explanation blue bibcodes open ADS page with paths to full text
Author name code: mueller-edith
ADS astronomy entries on 2022-09-14
author:"Mueller, Edith A."
---------------------------------------------------------
Title: Overview of the Instrumentation for the Dark Energy
Spectroscopic Instrument
Authors: Abareshi, B.; Aguilar, J.; Ahlen, S.; Alam, Shadab; Alexander,
David M.; Alfarsy, R.; Allen, L.; Allende Prieto, C.; Alves, O.;
Ameel, J.; Armengaud, E.; Asorey, J.; Aviles, Alejandro; Bailey,
S.; Balaguera-Antolínez, A.; Ballester, O.; Baltay, C.; Bault,
A.; Beltran, S. F.; Benavides, B.; BenZvi, S.; Berti, A.; Besuner,
R.; Beutler, Florian; Bianchi, D.; Blake, C.; Blanc, P.; Blum, R.;
Bolton, A.; Bose, S.; Bramall, D.; Brieden, S.; Brodzeller, A.;
Brooks, D.; Brownewell, C.; Buckley-Geer, E.; Cahn, R. N.; Cai, Z.;
Canning, R.; Carnero Rosell, A.; Carton, P.; Casas, R.; Castander,
F. J.; Cervantes-Cota, J. L.; Chabanier, S.; Chaussidon, E.; Chuang,
C.; Circosta, C.; Cole, S.; Cooper, A. P.; da Costa, L.; Cousinou,
M. -C.; Cuceu, A.; Davis, T. M.; Dawson, K.; de la Cruz-Noriega, R.;
de la Macorra, A.; de Mattia, A.; Della Costa, J.; Demmer, P.; Derwent,
M.; Dey, A.; Dey, B.; Dhungana, G.; Ding, Z.; Dobson, C.; Doel, P.;
Donald-McCann, J.; Donaldson, J.; Douglass, K.; Duan, Y.; Dunlop, P.;
Edelstein, J.; Eftekharzadeh, S.; Eisenstein, D. J.; Enriquez-Vargas,
M.; Escoffier, S.; Evatt, M.; Fagrelius, P.; Fan, X.; Fanning, K.;
Fawcett, V. A.; Ferraro, S.; Ereza, J.; Flaugher, B.; Font-Ribera,
A.; Forero-Romero, J. E.; Frenk, C. S.; Fromenteau, S.; Gänsicke,
B. T.; Garcia-Quintero, C.; Garrison, L.; Gaztañaga, E.; Gerardi,
F.; Gil-Marín, H.; Gontcho, S. Gontcho A; Gonzalez-Morales, Alma
X.; Gonzalez-de-Rivera, G.; Gonzalez-Perez, V.; Gordon, C.; Graur,
O.; Green, D.; Grove, C.; Gruen, D.; Gutierrez, G.; Guy, J.; Hahn,
C.; Harris, S.; Herrera, D.; Herrera-Alcantar, Hiram K.; Honscheid,
K.; Howlett, C.; Huterer, D.; Iršič, V.; Ishak, M.; Jelinsky, P.;
Jiang, L.; Jimenez, J.; Jing, Y. P.; Joyce, R.; Jullo, E.; Juneau,
S.; Karaçaylı, N. G.; Karamanis, M.; Karcher, A.; Karim, T.; Kehoe,
R.; Kent, S.; Kirkby, D.; Kisner, T.; Kitaura, F.; Koposov, S. E.;
Kovács, A.; Kremin, A.; Krolewski, Alex; L'Huillier, B.; Lahav,
O.; Lambert, A.; Lamman, C.; Lan, Ting-Wen; Landriau, M.; Lane, S.;
Lang, D.; Lange, J. U.; Lasker, J.; Le Guillou, L.; Leauthaud, A.;
Le Van Suu, A.; Levi, Michael E.; Li, T. S.; Magneville, C.; Manera,
M.; Manser, Christopher J.; Marshall, B.; McCollam, W.; McDonald, P.;
Meisner, Aaron M.; Mezcua, J. Mena-Fernández M.; Miller, T.; Miquel,
R.; Montero-Camacho, P.; Moon, J.; Martini, J. Paul; Meneses-Rizo, J.;
Moustakas, J.; Mueller, E.; Muñoz-Gutiérrez, Andrea; Myers, Adam D.;
Nadathur, S.; Najita, J.; Napolitano, L.; Neilsen, E.; Newman, Jeffrey
A.; Nie, J. D.; Ning, Y.; Niz, G.; Norberg, P.; Noriega, Hernán E.;
O'Brien, T.; Obuljen, A.; Palanque-Delabrouille, N.; Palmese, A.;
Zhiwei, P.; Pappalardo, D.; Peng, X.; Percival, W. J.; Perruchot,
S.; Pogge, R.; Poppett, C.; Porredon, A.; Prada, F.; Prochaska, J.;
Pucha, R.; Pérez-Fernández, A.; Pérez-Ráfols, I.; Rabinowitz, D.;
Raichoor, A.; Ramirez-Solano, S.; Ramírez-Pérez, César; Ravoux, C.;
Reil, K.; Rezaie, M.; Rocher, A.; Rockosi, C.; Roe, N. A.; Roodman,
A.; Ross, A. J.; Rossi, G.; Ruggeri, R.; Ruhlmann-Kleider, V.; Sabiu,
C. G.; Safonova, S.; Said, K.; Saintonge, A.; Salas Catonga, Javier;
Samushia, L.; Sanchez, E.; Saulder, C.; Schaan, E.; Schlafly, E.;
Schlegel, D.; Schmoll, J.; Scholte, D.; Schubnell, M.; Secroun,
A.; Seo, H.; Serrano, S.; Sharples, Ray M.; Sholl, Michael J.;
Silber, Joseph Harry; Silva, D. R.; Sirk, M.; Siudek, M.; Smith, A.;
Sprayberry, D.; Staten, R.; Stupak, B.; Tan, T.; Tarlé, Gregory; Sien
Tie, Suk; Tojeiro, R.; Ureña-López, L. A.; Valdes, F.; Valenzuela,
O.; Valluri, M.; Vargas-Magaña, M.; Verde, L.; Walther, M.; Wang,
B.; Wang, M. S.; Weaver, B. A.; Weaverdyck, C.; Wechsler, R.; Wilson,
Michael J.; Yang, J.; Yu, Y.; Yuan, S.; Yèche, Christophe; Zhang,
H.; Zhang, K.; Zhao, Cheng; Zhou, Rongpu; Zhou, Zhimin; Zou, H.; Zou,
J.; Zou, S.; Zu, Y.
2022arXiv220510939A Altcode:
The Dark Energy Spectroscopic Instrument (DESI) has embarked on an
ambitious five-year survey to explore the nature of dark energy with
spectroscopy of 40 million galaxies and quasars. DESI will determine
precise redshifts and employ the Baryon Acoustic Oscillation
method to measure distances from the nearby universe to z >
3.5, as well as measure the growth of structure and probe potential
modifications to general relativity. In this paper we describe the
significant instrumentation we developed for the DESI survey. The new
instrumentation includes a wide-field, 3.2-deg diameter prime-focus
corrector that focuses the light onto 5020 robotic fiber positioners
on the 0.812 m diameter, aspheric focal surface. The positioners and
their fibers are divided among ten wedge-shaped petals. Each petal is
connected to one of ten spectrographs via a contiguous, high-efficiency,
nearly 50 m fiber cable bundle. The ten spectrographs each use a pair of
dichroics to split the light into three channels that together record
the light from 360 - 980 nm with a resolution of 2000 to 5000. We
describe the science requirements, technical requirements on the
instrumentation, and management of the project. DESI was installed at
the 4-m Mayall telescope at Kitt Peak, and we also describe the facility
upgrades to prepare for DESI and the installation and functional
verification process. DESI has achieved all of its performance goals,
and the DESI survey began in May 2021. Some performance highlights
include RMS positioner accuracy better than 0.1", SNR per \sqrtÅ >
0.5 for a z > 2 quasar with flux 0.28e-17 erg/s/cm^2/A at 380 nm
in 4000s, and median SNR = 7 of the [OII] doublet at 8e-17 erg/s/cm^2
in a 1000s exposure for emission line galaxies at z = 1.4 - 1.6. We
conclude with highlights from the on-sky validation and commissioning
of the instrument, key successes, and lessons learned. (abridged)
---------------------------------------------------------
Title: Classification of 11 supernovae by DEBass
Authors: Lidman, C.; Dhaka, S.; Hall, M.; Melton, M.; Muller, E.;
Ireland, M.; Sharp, R.; Abbot, H.; Armstrong, P.; Taylor, G.; Tucker,
B. E.; Brout, D.
2021ATel14925....1L Altcode:
We report spectroscopic classifications and redshifts of 11 supernovae
observed by DEBass. The targets were supplied by ATLAS and ZTF. The
spectra (350-900nm) were obtained with the WiFeS instrument (Dopita
et al. 2007 Ap & SS, 327, 245) on the ANU 2.3-metre telescope.
---------------------------------------------------------
Title: Supernova 1987A: 3D Mixing and Light Curves for Explosion
Models Based on Binary-merger Progenitors
Authors: Utrobin, V. P.; Wongwathanarat, A.; Janka, H. -Th.; Müller,
E.; Ertl, T.; Menon, A.; Heger, A.
2021ApJ...914....4U Altcode: 2021arXiv210209686U
Six binary-merger progenitors of supernova 1987A (SN 1987A) with
properties close to those of the blue supergiant Sanduleak -69°202
are exploded by neutrino heating and evolved until long after
shock breakout in 3D and continued for light-curve calculations
in spherical symmetry. Our results confirm previous findings for
single-star progenitors: (1) 3D neutrino-driven explosions with SN
1987A-like energies synthesize <SUP>56</SUP>Ni masses consistent
with the radioactive light-curve tail; (2) hydrodynamic models mix
hydrogen inward to minimum velocities below 40 km s<SUP>-1</SUP>
compatible with spectral observations of SN 1987A; and (3) for given
explosion energy the efficiency of outward radioactive <SUP>56</SUP>Ni
mixing depends mainly on high growth factors of Rayleigh-Taylor
instabilities at the (C+O)/He and He/H composition interfaces and a
weak interaction of fast plumes with the reverse shock occurring below
the He/H interface. All binary-merger models possess presupernova
radii matching the photometric radius of Sanduleak -69°202 and a
structure of the outer layers allowing them to reproduce the observed
initial luminosity peak in the first ~7 days. Models that mix about
0.5 M<SUB>⊙</SUB> of hydrogen into the He-shell and exhibit strong
outward mixing of <SUP>56</SUP>Ni with maximum velocities exceeding the
3000 km s<SUP>-1</SUP> observed for the bulk of ejected <SUP>56</SUP>Ni
have light-curve shapes in good agreement with the dome of the SN 1987A
light curve. A comparative analysis of the best representatives of our
3D neutrino-driven explosion models of SN 1987A based on single-star and
binary-merger progenitors reveals that only one binary model fulfills
all observational constraints, except one.
---------------------------------------------------------
Title: Calibrating core overshooting parameters with two-dimensional
hydrodynamical simulations
Authors: Higl, J.; Müller, E.; Weiss, A.
2021A&A...646A.133H Altcode: 2020arXiv201205262H
The extent of mixed regions around convective zones is one of the
biggest uncertainties in stellar evolution. One-dimensional overshooting
descriptions introduce a free parameter (f<SUB>ov</SUB>) that is,
in general, not well constrained from observations. Especially
in small central convective regions, the value is highly
uncertain due to its tight connection to the pressure scale
height. Long-term multi-dimensional hydrodynamic simulations can
be used to study the size of the overshooting region as well as
the involved mixing processes. Here we show how one can calibrate
an overshooting parameter by performing two-dimensional Maestro
simulations of zero-age-main-sequence stars ranging from 1.3 to 3.5
M<SUB>⊙</SUB>. The simulations cover the convective cores of the stars
and a large fraction of the surrounding radiative envelope. We follow
the convective flow for at least 20 convective turnover times, while
the longest simulation covers 430 turnover time scales. This allows us
to study how the mixing as well as the convective boundary itself evolve
with time, and how the resulting entrainment can be interpreted in terms
of overshooting parameters. We find that increasing the overshooting
parameter f<SUB>ov</SUB> beyond a certain value in the initial model of
our simulations changes the mixing behaviour completely. This result can
be used to put limits on the overshooting parameter. We find 0.010 <
f<SUB>ov</SUB> < 0.017 to be in good agreement with our simulations
of a 3.5 M<SUB>⊙</SUB> mass star. We also identify a diffusive mixing
component due to internal gravity waves that is active throughout the
convectively stable layer, but it is most likely overestimated in our
simulations. Furthermore, applying our calibration method to simulations
of less massive stars suggests a need for a mass-dependent overshooting
description where the mixing in terms of the pressure scale height is
reduced for small convective cores.
---------------------------------------------------------
Title: ESPRESSO high-resolution transmission spectroscopy of WASP-76 b
Authors: Tabernero, H. M.; Zapatero Osorio, M. R.; Allart, R.; Borsa,
F.; Casasayas-Barris, N.; Demangeon, O.; Ehrenreich, D.; Lillo-Box,
J.; Lovis, C.; Pallé, E.; Sousa, S. G.; Rebolo, R.; Santos,
N. C.; Pepe, F.; Cristiani, S.; Adibekyan, V.; Allende Prieto, C.;
Alibert, Y.; Barros, S. C. C.; Bouchy, F.; Bourrier, V.; D'Odorico,
V.; Dumusque, X.; Faria, J. P.; Figueira, P.; Génova Santos, R.;
González Hernández, J. I.; Hojjatpanah, S.; Lo Curto, G.; Lavie,
B.; Martins, C. J. A. P.; Martins, J. H. C.; Mehner, A.; Micela,
G.; Molaro, P.; Nunes, N. J.; Poretti, E.; Seidel, J. V.; Sozzetti,
A.; Suárez Mascareño, A.; Udry, S.; Aliverti, M.; Affolter, M.;
Alves, D.; Amate, M.; Avila, G.; Bandy, T.; Benz, W.; Bianco, A.;
Broeg, C.; Cabral, A.; Conconi, P.; Coelho, J.; Cumani, C.; Deiries,
S.; Dekker, H.; Delabre, B.; Fragoso, A.; Genoni, M.; Genolet, L.;
Hughes, I.; Knudstrup, J.; Kerber, F.; Landoni, M.; Lizon, J. L.;
Maire, C.; Manescau, A.; Di Marcantonio, P.; Mégevand, D.; Monteiro,
M.; Monteiro, M.; Moschetti, M.; Mueller, E.; Modigliani, A.; Oggioni,
L.; Oliveira, A.; Pariani, G.; Pasquini, L.; Rasilla, J. L.; Redaelli,
E.; Riva, M.; Santana-Tschudi, S.; Santin, P.; Santos, P.; Segovia,
A.; Sosnowska, D.; Spanò, P.; Tenegi, F.; Iwert, O.; Zanutta, A.;
Zerbi, F.
2021A&A...646A.158T Altcode: 2020arXiv201112197T
<BR /> Aims: We report on ESPRESSO high-resolution transmission
spectroscopic observations of two primary transits of the highly
irradiated, ultra-hot Jupiter-sized planet, WASP-76b. We investigated
the presence of several key atomic and molecular features of interest
that may reveal the atmospheric properties of the planet. <BR />
Methods: We extracted two transmission spectra of WASP-76b with R ≈
140 000 using a procedure that allowed us to process the full ESPRESSO
wavelength range (3800-7880 Å) simultaneously. We observed that at
a high signal-to-noise ratio, the continuum of ESPRESSO spectra shows
`wiggles', which are likely caused by an interference pattern outside
the spectrograph. To search for the planetary features, we visually
analysed the extracted transmission spectra and cross-correlated
the observations against theoretical spectra of different atomic and
molecular species. <BR /> Results: The following atomic features are
detected: Li I, Na I, Mg I, Ca II, Mn I, K I, and Fe I. All are detected
with a confidence level between 9.2 σ (Na I) and 2.8 σ (Mg I). We did
not detect the following species: Ti I, Cr I, Ni I, TiO, VO, and ZrO. We
impose the following 1 σ upper limits on their detectability: 60,
77, 122, 6, 8, and 8 ppm, respectively. <BR /> Conclusions: We report
the detection of Li I on WASP-76b for the first time. In addition,
we confirm the presence of Na I and Fe I as previously reported in
the literature. We show that the procedure employed in this work can
detect features down to the level of ~0.1% in the transmission spectrum
and ~10 ppm by means of a cross-correlation method. We discuss the
presence of neutral and singly ionised features in the atmosphere of
WASP-76b. <P />Based on guaranteed time observations collected at the
European Southern Observatory under ESO programme 1102.C-0744 by the
ESPRESSO Consortium.
---------------------------------------------------------
Title: The SEDIGISM survey: First Data Release and overview of the
Galactic structure
Authors: Schuller, F.; Urquhart, J. S.; Csengeri, T.; Colombo,
D.; Duarte-Cabral, A.; Mattern, M.; Ginsburg, A.; Pettitt, A. R.;
Wyrowski, F.; Anderson, L.; Azagra, F.; Barnes, P.; Beltran, M.;
Beuther, H.; Billington, S.; Bronfman, L.; Cesaroni, R.; Dobbs, C.;
Eden, D.; Lee, M. -Y.; Medina, S. -N. X.; Menten, K. M.; Moore, T.;
Montenegro-Montes, F. M.; Ragan, S.; Rigby, A.; Riener, M.; Russeil,
D.; Schisano, E.; Sanchez-Monge, A.; Traficante, A.; Zavagno, A.;
Agurto, C.; Bontemps, S.; Finger, R.; Giannetti, A.; Gonzalez,
E.; Hernandez, A. K.; Henning, T.; Kainulainen, J.; Kauffmann, J.;
Leurini, S.; Lopez, S.; Mac-Auliffe, F.; Mazumdar, P.; Molinari, S.;
Motte, F.; Muller, E.; Nguyen-Luong, Q.; Parra, R.; Perez-Beaupuits,
J. -P.; Schilke, P.; Schneider, N.; Suri, S.; Testi, L.; Torstensson,
K.; Veena, V. S.; Venegas, P.; Wang, K.; Wienen, M.
2021MNRAS.500.3064S Altcode: 2020arXiv201201527S; 2020MNRAS.tmp.2600S; 2020MNRAS.500.3064S
The SEDIGISM (Structure, Excitation and Dynamics of the Inner
Galactic Interstellar Medium) survey used the APEX telescope to map 84
deg<SUP>2</SUP> of the Galactic plane between ℓ = -60° and +31°
in several molecular transitions, including <SUP>13</SUP>CO (2 -
1) and C<SUP>18</SUP>O (2 - 1), thus probing the moderately dense
(∼10<SUP>3</SUP> cm<SUP>-3</SUP>) component of the interstellar
medium. With an angular resolution of 30 arcsec and a typical 1σ
sensitivity of 0.8-1.0 K at 0.25 km s<SUP>-1</SUP> velocity resolution,
it gives access to a wide range of structures, from individual
star-forming clumps to giant molecular clouds and complexes. The
coverage includes a good fraction of the first and fourth Galactic
quadrants, allowing us to constrain the large-scale distribution of
cold molecular gas in the inner Galaxy. In this paper, we provide an
updated overview of the full survey and the data reduction procedures
used. We also assess the quality of these data and describe the data
products that are being made publicly available as part of this First
Data Release (DR1). We present integrated maps and position-velocity
maps of the molecular gas and use these to investigate the correlation
between the molecular gas and the large-scale structural features
of the Milky Way such as the spiral arms, Galactic bar and Galactic
Centre. We find that approximately 60 per cent of the molecular
gas is associated with the spiral arms and these appear as strong
intensity peaks in the derived Galactocentric distribution. We also
find strong peaks in intensity at specific longitudes that correspond
to the Galactic Centre and well-known star-forming complexes, revealing
that the <SUP>13</SUP>CO emission is concentrated in a small number
of complexes rather than evenly distributed along spiral arms.
---------------------------------------------------------
Title: The SEDIGISM survey: molecular clouds in the inner Galaxy
Authors: Duarte-Cabral, A.; Colombo, D.; Urquhart, J. S.; Ginsburg,
A.; Russeil, D.; Schuller, F.; Anderson, L. D.; Barnes, P. J.;
Beltrán, M. T.; Beuther, H.; Bontemps, S.; Bronfman, L.; Csengeri,
T.; Dobbs, C. L.; Eden, D.; Giannetti, A.; Kauffmann, J.; Mattern,
M.; Medina, S. -N. X.; Menten, K. M.; Lee, M. -Y.; Pettitt, A. R.;
Riener, M.; Rigby, A. J.; Traficante, A.; Veena, V. S.; Wienen,
M.; Wyrowski, F.; Agurto, C.; Azagra, F.; Cesaroni, R.; Finger,
R.; Gonzalez, E.; Henning, T.; Hernandez, A. K.; Kainulainen, J.;
Leurini, S.; Lopez, S.; Mac-Auliffe, F.; Mazumdar, P.; Molinari, S.;
Motte, F.; Muller, E.; Nguyen-Luong, Q.; Parra, R.; Perez-Beaupuits,
J. -P.; Montenegro-Montes, F. M.; Moore, T. J. T.; Ragan, S. E.;
Sánchez-Monge, A.; Sanna, A.; Schilke, P.; Schisano, E.; Schneider,
N.; Suri, S.; Testi, L.; Torstensson, K.; Venegas, P.; Wang, K.;
Zavagno, A.
2021MNRAS.500.3027D Altcode: 2020MNRAS.tmp.2609D; 2020arXiv201201502D; 2020MNRAS.500.3027D
We use the <SUP>13</SUP>CO (2-1) emission from the SEDIGISM (Structure,
Excitation, and Dynamics of the Inner Galactic InterStellar Medium)
high-resolution spectral-line survey of the inner Galaxy, to extract
the molecular cloud population with a large dynamic range in spatial
scales, using the Spectral Clustering for Interstellar Molecular
Emission Segmentation (SCIMES) algorithm. This work compiles a cloud
catalogue with a total of 10 663 molecular clouds, 10 300 of which
we were able to assign distances and compute physical properties. We
study some of the global properties of clouds using a science sample,
consisting of 6664 well-resolved sources and for which the distance
estimates are reliable. In particular, we compare the scaling relations
retrieved from SEDIGISM to those of other surveys, and we explore the
properties of clouds with and without high-mass star formation. Our
results suggest that there is no single global property of a cloud
that determines its ability to form massive stars, although we
find combined trends of increasing mass, size, surface density,
and velocity dispersion for the sub-sample of clouds with ongoing
high-mass star formation. We then isolate the most extreme clouds in
the SEDIGISM sample (i.e. clouds in the tails of the distributions)
to look at their overall Galactic distribution, in search for hints of
environmental effects. We find that, for most properties, the Galactic
distribution of the most extreme clouds is only marginally different
to that of the global cloud population. The Galactic distribution of
the largest clouds, the turbulent clouds and the high-mass star-forming
clouds are those that deviate most significantly from the global cloud
population. We also find that the least dynamically active clouds
(with low velocity dispersion or low virial parameter) are situated
further afield, mostly in the least populated areas. However, we suspect
that part of these trends may be affected by some observational biases
(such as completeness and survey limitations), and thus require further
follow up work in order to be confirmed.
---------------------------------------------------------
Title: A precise architecture characterization of the π Mensae
planetary system
Authors: Damasso, M.; Sozzetti, A.; Lovis, C.; Barros, S. C. C.; Sousa,
S. G.; Demangeon, O. D. S.; Faria, J. P.; Lillo-Box, J.; Cristiani,
S.; Pepe, F.; Rebolo, R.; Santos, N. C.; Zapatero Osorio, M. R.;
González Hernández, J. I.; Amate, M.; Pasquini, L.; Zerbi, F. M.;
Adibekyan, V.; Abreu, M.; Affolter, M.; Alibert, Y.; Aliverti, M.;
Allart, R.; Allende Prieto, C.; Álvarez, D.; Alves, D.; Avila, G.;
Baldini, V.; Bandy, T.; Benz, W.; Bianco, A.; Borsa, F.; Bossini,
D.; Bourrier, V.; Bouchy, F.; Broeg, C.; Cabral, A.; Calderone,
G.; Cirami, R.; Coelho, J.; Conconi, P.; Coretti, I.; Cumani, C.;
Cupani, G.; D'Odorico, V.; Deiries, S.; Dekker, H.; Delabre, B.; Di
Marcantonio, P.; Dumusque, X.; Ehrenreich, D.; Figueira, P.; Fragoso,
A.; Genolet, L.; Genoni, M.; Génova Santos, R.; Hughes, I.; Iwert,
O.; Kerber, F.; Knudstrup, J.; Landoni, M.; Lavie, B.; Lizon, J. -L.;
Lo Curto, G.; Maire, C.; Martins, C. J. A. P.; Mégevand, D.; Mehner,
A.; Micela, G.; Modigliani, A.; Molaro, P.; Monteiro, M. A.; Monteiro,
M. J. P. F. G.; Moschetti, M.; Mueller, E.; Murphy, M. T.; Nunes,
N.; Oggioni, L.; Oliveira, A.; Oshagh, M.; Pallé, E.; Pariani, G.;
Poretti, E.; Rasilla, J. L.; Rebordão, J.; Redaelli, E. M.; Riva, M.;
Santana Tschudi, S.; Santin, P.; Santos, P.; Ségransan, D.; Schmidt,
T. M.; Segovia, A.; Sosnowska, D.; Spanò, P.; Suárez Mascareño,
A.; Tabernero, H.; Tenegi, F.; Udry, S.; Zanutta, A.
2020A&A...642A..31D Altcode: 2020arXiv200706410D
Context. The bright star π Men was chosen as the first target for a
radial velocity follow-up to test the performance of ESPRESSO, the new
high-resolution spectrograph at the European Southern Observatory's Very
Large Telescope. The star hosts a multi-planet system (a transiting
4 M<SUB>⊕</SUB> planet at ~0.07 au and a sub-stellar companion on
a ~2100-day eccentric orbit), which is particularly suitable for a
precise multi-technique characterization. <BR /> Aims: With the new
ESPRESSO observations, which cover a time span of 200 days, we aim
to improve the precision and accuracy of the planet parameters and
search for additional low-mass companions. We also take advantage of
the new photometric transits of π Men c observed by TESS over a time
span that overlaps with that of the ESPRESSO follow-up campaign. <BR
/> Methods: We analysed the enlarged spectroscopic and photometric
datasets and compared the results to those in the literature. We
further characterized the system by means of absolute astrometry with
HIPPARCOS and Gaia. We used the high-resolution spectra of ESPRESSO for
an independent determination of the stellar fundamental parameters. <BR
/> Results: We present a precise characterization of the planetary
system around π Men. The ESPRESSO radial velocities alone (37 nightly
binned data with typical uncertainty of 10 cm s<SUP>-1</SUP>) allow
for a precise retrieval of the Doppler signal induced by π Men c. The
residuals show a root mean square of 1.2 m s<SUP>-1</SUP>, which is half
that of the HARPS data; based on the residuals, we put limits on the
presence of additional low-mass planets (e.g. we can exclude companions
with a minimum mass less than ~2 M<SUB>⊕</SUB> within the orbit of
π Men c). We improve the ephemeris of π Men c using 18 additional
TESS transits, and, in combination with the astrometric measurements,
we determine the inclination of the orbital plane of π Men b with high
precision (i<SUB>b</SUB> =45.8<SUB>-1.1</SUB><SUP>+1.4</SUP> deg). This
leads to the precise measurement of its absolute mass m<SUB>b</SUB>
=14.1<SUB>-0.4</SUB><SUP>+0.5</SUP> M<SUB>Jup</SUB>, indicating that π
Men b can be classified as a brown dwarf. <BR /> Conclusions: The π
Men system represents a nice example of the extreme precision radial
velocities that can be obtained with ESPRESSO for bright targets. Our
determination of the 3D architecture of the π Men planetary system
and the high relative misalignment of the planetary orbital planes put
constraints on and challenge the theories of the formation and dynamical
evolution of planetary systems. The accurate measurement of the mass of
π Men b contributes to make the brown dwarf desert a bit greener. <P
/>Tables B.1 and B.2 are only available at the CDS via anonymous ftp to
<A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/642/A31">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/642/A31</A>
<P />Based (in part) on Guaranteed Time Observations collected at the
European Southern Observatory (ESO) under ESO programme(s) 1102.C-0744,
1102.C-0958, and 1104.C-0350 by the ESPRESSO Consortium.
---------------------------------------------------------
Title: Characterization of the K2-38 planetary system. Unraveling
one of the densest planets known to date
Authors: Toledo-Padrón, B.; Lovis, C.; Suárez Mascareño, A.;
Barros, S. C. C.; González Hernández, J. I.; Sozzetti, A.; Bouchy,
F.; Zapatero Osorio, M. R.; Rebolo, R.; Cristiani, S.; Pepe, F. A.;
Santos, N. C.; Sousa, S. G.; Tabernero, H. M.; Lillo-Box, J.; Bossini,
D.; Adibekyan, V.; Allart, R.; Damasso, M.; D'Odorico, V.; Figueira,
P.; Lavie, B.; Lo Curto, G.; Mehner, A.; Micela, G.; Modigliani,
A.; Nunes, N. J.; Pallé, E.; Abreu, M.; Affolter, M.; Alibert, Y.;
Aliverti, M.; Allende Prieto, C.; Alves, D.; Amate, M.; Avila, G.;
Baldini, V.; Bandy, T.; Benatti, S.; Benz, W.; Bianco, A.; Broeg,
C.; Cabral, A.; Calderone, G.; Cirami, R.; Coelho, J.; Conconi,
P.; Coretti, I.; Cumani, C.; Cupani, G.; Deiries, S.; Dekker, H.;
Delabre, B.; Demangeon, O.; Di Marcantonio, P.; Ehrenreich, D.;
Fragoso, A.; Genolet, L.; Genoni, M.; Génova Santos, R.; Hughes,
I.; Iwert, O.; Knudstrup, J.; Landoni, M.; Lizon, J. L.; Maire,
C.; Manescau, A.; Martins, C. J. A. P.; Mégevand, D.; Molaro, P.;
Monteiro, M. J. P. F. G.; Monteiro, M. A.; Moschetti, M.; Mueller,
E.; Oggioni, L.; Oliveira, A.; Oshagh, M.; Pariani, G.; Pasquini, L.;
Poretti, E.; Rasilla, J. L.; Redaelli, E.; Riva, M.; Santana Tschudi,
S.; Santin, P.; Santos, P.; Segovia, A.; Sosnowska, D.; Spanò, P.;
Tenegi, F.; Udry, S.; Zanutta, A.; Zerbi, F.
2020A&A...641A..92T Altcode: 2020arXiv200701081T
Context. An accurate characterization of the known exoplanet population
is key to understanding the origin and evolution of planetary
systems. Determining true planetary masses through the radial velocity
(RV) method is expected to experience a great improvement thanks to
the availability of ultra-stable echelle spectrographs. <BR /> Aims: We
took advantage of the extreme precision of the new-generation echelle
spectrograph ESPRESSO to characterize the transiting planetary system
orbiting the G2V star K2-38 located at 194 pc from the Sun with V ~
11.4. This system is particularly interesting because it could contain
the densest planet detected to date. <BR /> Methods: We carried out
a photometric analysis of the available K2 photometric light curve of
this star to measure the radius of its two known planets, K2-38b and
K2-38c, with P<SUB>b</SUB> = 4.01593 ± 0.00050 d and P<SUB>c</SUB> =
10.56103 ± 0.00090 d, respectively. Using 43 ESPRESSO high-precision
RV measurements taken over the course of 8 months along with the 14
previously published HIRES RV measurements, we modeled the orbits
of the two planets through a Markov chain Monte Carlo analysis,
significantly improving their mass measurements. <BR /> Results: Using
ESPRESSO spectra, we derived the stellar parameters, T<SUB>eff</SUB>
= 5731 ± 66, log g = 4.38 ± 0.11 dex, and [Fe/H] = 0.26 ±
0.05 dex, and thus the mass and radius of K2-38, M<SUB>⋆</SUB> =
1.03<SUB>-0.02</SUB><SUP>+0.04</SUP> M<SUB>⊕</SUB> and R<SUB>⋆</SUB>
= 1.06<SUB>-0.06</SUB><SUP>+0.09</SUP> R<SUB>⊕</SUB>. We
determine new values for the planetary properties of both planets. We
characterize K2-38b as a super-Earth with R<SUB>P</SUB> = 1.54 ± 0.14
R<SUB>⊕</SUB> and M<SUB>p</SUB> = 7.3<SUB>-1.0</SUB><SUP>+1.1</SUP>
M<SUB>⊕</SUB>, and K2-38c as a sub-Neptune with
R<SUB>P</SUB> = 2.29 ± 0.26 R<SUB>⊕</SUB> and M<SUB>p</SUB> =
8.3<SUB>-1.3</SUB><SUP>+1.3</SUP> M<SUB>⊕</SUB>. Combining the radius
and mass measurements, we derived a mean density of ρ<SUB>p</SUB> =
11.0<SUB>-2.8</SUB><SUP>+4.1</SUP> g cm<SUP>-3</SUP> for K2-38b and
ρ<SUB>p</SUB> = 3.8<SUB>-1.1</SUB><SUP>+1.8</SUP> g cm<SUP>-3</SUP>
for K2-38c, confirming K2-38b as one of the densest planets known to
date. <BR /> Conclusions: The best description for the composition
of K2-38b comes from an iron-rich Mercury-like model, while K2-38c
is better described by a rocky-model with H2 envelope. The maximum
collision stripping boundary shows how giant impacts could be the cause
for the high density of K2-38b. The irradiation received by each planet
places them on opposite sides of the radius valley. We find evidence of
a long-period signal in the RV time-series whose origin could be linked
to a 0.25-3 M<SUB>J</SUB> planet or stellar activity. <P />The ESPRESSO
RVs used in this paper are only available at the CDS via anonymous ftp
to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/641/A92">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/641/A92</A>
<P />Based (in part) on Guaranteed Time Observations collected at
the European Southern Observatory under ESO programmes1102.C-0744,
112.C-0958, and 1104.C-0350 by the ESPRESSO Consortium.
---------------------------------------------------------
Title: VizieR Online Data Catalog: pi Men radial velocity curves
(Damasso+, 2020)
Authors: Damasso, M.; Sozzetti, A.; Lovis, C.; Barros, S. C. C.; Sousa,
S. G.; Demangeon, O. D. S.; Faria, J. P.; Lillo-Box, J.; Cristiani,
S.; Pepe, F.; Rebolo, R.; Santos, N. C.; Zapatero Osorio, M. R.;
Gonzalez Hernandez, J. I.; Amate, M.; Pasquini, L.; Zerbi, F. M.;
Adibekyan, V.; Abreu, M.; Aolter, M.; Alibert, Y.; Aliverti, M.;
Allart, R.; Allende Prieto, C.; Alvarez, D.; Alves, D.; Avila, G.;
Baldini, V.; Bandy, T.; Benz, W.; Bianco, A.; Borsa, F.; Bossini,
D.; Bourrier, V.; Bouchy, F.; Broeg, C.; Cabral, A.; Calderone,
G.; Cirami, R.; Coelho, J.; Conconi, P.; Coretti, I.; Cumani, C.;
Cupani, G.; D'Odorico, V.; Deiries, S.; Dekker, H.; Delabre, B.; di
Marcantonio, P.; Dumusque, X.; Ehrenreich, D.; Figueira, P.; Fragoso,
A.; Genolet, L.; Genoni, M.; Genova Santos, R.; Hughes, I.; Iwert,
O.; F. Kerber; Knudstrup, J.; Landoni, M.; Lavie, B.; Lizon, J. -L.;
Lo Curto, G.; Maire, C.; J. A. P. Martins, C.; Megevand, D.; Mehner,
A.; Micela, G.; Modigliani, A.; Molaro, P.; Monteiro, M. A.; Monteiro,
M. J. P. F. G.; Moschetti, M.; Mueller, E.; Murphy, M. T.; Nunes,
N.; Oggioni, L.; Olive, Ira A.; Oshagh, M.; Palle, E.; Pariani, G.;
Poretti, E.; Rasilla, J. L.; Rebordao, J.; Redaelli, E. M.; Riva, M.;
Santana Tschudi, S.; Santin, P.; Santos, P.; Segransan, D.; Schmidt,
T. M.; Segovia, A.; Sosnowska, D.; Spano, P.; Suarez Mascareno, A.;
Tabernero, H.; Tenegi, F.; Udry, S.; Zanutta, A.
2020yCat..36420031D Altcode:
The observations of pi Men with ESPRESSO (using the instrument in single
Unit Telescope mode with a median resolving power R=138000 over the
378.2 and 788.7nm wavelength range) were carried out within one of the
sub-programmes of the Guaranteed Time Observations (GTOs), aimed at
using the very precise RVs to characterize (i.e. measure masses and
bulk densities) transiting planets discovered by TESS and Kepler's
second light K2 mission (see Pepe et al. 2020 (A&A, submitted)
for a detailed discussion of the ESPRESSO on-sky performance). The
pi Men system was observed starting from September 2018, right
before the end of the commissioning phase of the instrument, up to
March 2019. We collected 275 spectra over 37 nights (multiple and
consecutive exposures per night) during a total time span of 201
days. The spectra were acquired with a typical exposure time of 120s,
providing a median signal-to-noise ratio S/N=243 per extracted pixel
at λ=500nm. In this work we also use previously unreleased spectra
from CORALIE to extract additional RVs. The pi Men system was observed
with CORALIE from November 1998 to February 2020, during which time 60
spectra with typical exposure times of 300-600s (S/N=82-124 at 550nm)
were collected. <P />Radial velocities extracted from ESPRESSO and
CORALIE spectra, and spectroscopic stellar activity diagnostics from
ESPRESSO. <P />(2 data files).
---------------------------------------------------------
Title: Revisiting Proxima with ESPRESSO
Authors: Suárez Mascareño, A.; Faria, J. P.; Figueira, P.; Lovis,
C.; Damasso, M.; González Hernández, J. I.; Rebolo, R.; Cristiani,
S.; Pepe, F.; Santos, N. C.; Zapatero Osorio, M. R.; Adibekyan, V.;
Hojjatpanah, S.; Sozzetti, A.; Murgas, F.; Abreu, M.; Affolter, M.;
Alibert, Y.; Aliverti, M.; Allart, R.; Allende Prieto, C.; Alves,
D.; Amate, M.; Avila, G.; Baldini, V.; Bandi, T.; Barros, S. C. C.;
Bianco, A.; Benz, W.; Bouchy, F.; Broeng, C.; Cabral, A.; Calderone,
G.; Cirami, R.; Coelho, J.; Conconi, P.; Coretti, I.; Cumani, C.;
Cupani, G.; D'Odorico, V.; Deiries, S.; Delabre, B.; Di Marcantonio,
P.; Dumusque, X.; Ehrenreich, D.; Fragoso, A.; Genolet, L.; Genoni,
M.; Génova Santos, R.; Hughes, I.; Iwert, O.; Kerber, F.; Knusdstrup,
J.; Landoni, M.; Lavie, B.; Lillo-Box, J.; Lizon, J.; Lo Curto, G.;
Maire, C.; Manescau, A.; Martins, C. J. A. P.; Mégevand, D.; Mehner,
A.; Micela, G.; Modigliani, A.; Molaro, P.; Monteiro, M. A.; Monteiro,
M. J. P. F. G.; Moschetti, M.; Mueller, E.; Nunes, N. J.; Oggioni,
L.; Oliveira, A.; Pallé, E.; Pariani, G.; Pasquini, L.; Poretti, E.;
Rasilla, J. L.; Redaelli, E.; Riva, M.; Santana Tschudi, S.; Santin,
P.; Santos, P.; Segovia, A.; Sosnowska, D.; Sousa, S.; Spanò, P.;
Tenegi, F.; Udry, S.; Zanutta, A.; Zerbi, F.
2020A&A...639A..77S Altcode: 2020arXiv200512114S
Context. The discovery of Proxima b marked one of the most important
milestones in exoplanetary science in recent years. Yet the limited
precision of the available radial velocity data and the difficulty
in modelling the stellar activity calls for a confirmation of the
Earth-mass planet. <BR /> Aims: We aim to confirm the presence
of Proxima b using independent measurements obtained with the new
ESPRESSO spectrograph, and refine the planetary parameters taking
advantage of its improved precision. <BR /> Methods: We analysed 63
spectroscopic ESPRESSO observations of Proxima (Gl 551) taken during
2019. We obtained radial velocity measurements with a typical radial
velocity photon noise of 26 cm s<SUP>-1</SUP>. We combined these data
with archival spectroscopic observations and newly obtained photometric
measurements to model the stellar activity signals and disentangle
them from planetary signals in the radial velocity (RV) data. We ran a
joint Markov chain Monte Carlo analysis on the time series of the RV and
full width half maximum of the cross-correlation function to model the
planetary and stellar signals present in the data, applying Gaussian
process regression to deal with the stellar activity signals. <BR />
Results: We confirm the presence of Proxima b independently in the
ESPRESSO data and in the combined ESPRESSO+ HARPS+UVES dataset. The
ESPRESSO data on its own shows Proxima b at a period of 11.218 ±
0.029 days, with a minimum mass of 1.29 ± 0.13 M<SUB>⊕</SUB>. In
the combined dataset we measure a period of 11.18427 ± 0.00070 days
with a minimum mass of 1.173 ± 0.086 M<SUB>⊕</SUB>. We get a clear
measurement of the stellar rotation period (87 ± 12 d) and its induced
RV signal, but no evidence of stellar activity as a potential cause
for the 11.2 days signal. We find some evidence for the presence
of a second short-period signal, at 5.15 days with a semi-amplitude
of only 40 cm s<SUP>-1</SUP>. If caused by a planetary companion, it
would correspond to a minimum mass of 0.29 ± 0.08 M<SUB>⊕</SUB>. We
find that forthe case of Proxima, the full width half maximum of the
cross-correlation function can be used as a proxy for the brightness
changes and that its gradient with time can be used to successfully
detrend the RV data from part of the influence of stellar activity. The
activity-induced RV signal in the ESPRESSO data shows a trend in
amplitude towards redder wavelengths. Velocities measured using the
red end of the spectrograph are less affected by activity, suggesting
that the stellar activity is spot dominated. This could be used to
create differential RVs that are activity dominated and can be used to
disentangle activity-induced and planetary-induced signals. The data
collected excludes the presence of extra companions with masses above
0.6 M<SUB>⊕</SUB> at periods shorter than 50 days. <P />The data used
in this paper are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/639/A77">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/639/A77</A>
<P />Based [in part] on Guaranteed Time Observations collected at the
European Southern Observatory under ESO programme 1102.C-0744. by the
ESPRESSO Consortium. <P />This work makes use of observations from
the LCOGT network.
---------------------------------------------------------
Title: VizieR Online Data Catalog: K2-38 ESPRESSO RVs (Toledo-Padron+,
2020)
Authors: Toledo-Padron B. . Lovis, C.; Suarez Mascareno, A.; Barros,
S. C. C.; Gonzalez Hernandez, J. I.; Sozzetti, A.; Bouchy, F.; Zapatero
Osorio, M. R.; Rebolo, R.; Cristiani, S.; Pepe, F. A.; Santos, N. C.;
Sousa, S. G.; Tabernero, H. M.; Lillo-Box, J.; Bossini, D.; Adibekyan,
V.; Allart, R.; Damasso, M.; D'Odorico, V.; Figueira, P.; Lavie, B.;
Lo Curto, G.; Mehner, A.; Micela, G.; Modigliani, A.; Nunes, N. J.;
Palle, E.; Abreu, M.; Affolter, M.; Alibert, Y.; Aliverti, M.; Allende
Prieto, C.; Alves, D.; Amate, M.; Avila, G.; Baldini, V.; Bandy, T.;
Benatti, S.; Benz, W.; Bianco, A.; Broeg, C.; Cabral, A.; Calderone,
G.; Cirami, R.; Coelho, J.; Conconi, P.; Coretti, I.; Cumani, C.;
Cupani, G.; Deiries, S.; Dekker, H.; Delabre, B.; Demangeon, O.; di
Marcantonio, P.; Ehrenreich, D.; Fragoso, A.; Genolet, L.; Genoni, M.;
Genova Santos, R.; Hughes, I.; Iwert, O.; Knudstrup, J.; Landoni, M.;
Lizon, J. L.; Maire, C.; Manescau, A.; Martins, C. J. A. P.; Megevand,
D.; Molaro, P.; Monteiro, M. J. P. F. G.; Monteiro, M. A.; Moschetti,
M.; Mueller, E.; Oggioni, L.; Oliveira, A.; O'Shagh, M.; Pariani, G.;
Pasquini, L.; Poretti, E.; Rasilla, J. L.; Redaelli, E.; Riva, M.;
Santana Tschudi, S.; Santin, P.; Santos, P.; Segovia, A.; Sosnowska,
D.; Spano, P.; Tenegi, F.; Udry, S.; Zanutta, A.; Zerbi, F.
2020yCat..36410092T Altcode:
We used the public version of the ESPRESSO pipeline
Data-Reduction-Software (DRS) to compute the RVs of K2-38. The pipeline
provides a crosscorrelation function (CCF) for each spectrum using a G2
mask that covers the entire wavelength range of the instrument (between
3800 and 7880Å). The CCFs were built using a RV step of 0.5km/s within
a range between -55 and -15km/s centered on the systemic velocity of
the star. This RV time-series presents a RV precision of 1.0m/s with a
RMS of 3.6m/s, an extremely good result for a relatively faint G2 star
(V=11.34) like K2-38. <P />(1 data file).
---------------------------------------------------------
Title: The origin of continental carbonates in Andean salars:
A multi-tracer geochemical approach in Laguna Pastos Grandes (Bolivia)
Authors: Muller, E.; Gaucher, E. C.; Durlet, C.; Moquet, J. S.;
Moreira, M.; Rouchon, V.; Louvat, P.; Bardoux, G.; Noirez, S.;
Bougeault, C.; Vennin, E.; Gérard, E.; Chavez, M.; Virgone, A.;
Ader, M.
2020GeCoA.279..220M Altcode:
In continental volcanic settings, abundant carbonate precipitation
can occur with atypical facies compared to marine settings. The
(bio-)chemical processes responsible for their development and early
diagenesis are typically complex and not fully understood. In the
Bolivian Altiplano, Laguna Pastos Grandes hosts a 40-km<SUP>2</SUP>
carbonate platform with a great diversity of facies and provides an
ideal natural laboratory to understand the processes responsible for
the precipitation of carbonates in a continental province dominated
by volcanism. In order to trace the origin of both water and solutes
in the lagoon, the major element and stable isotope compositions
(δ<SUP>2</SUP>H-δ<SUP>18</SUP>O, δ<SUP>37</SUP>Cl, δ<SUP>7</SUP>Li,
δ<SUP>11</SUP>B and <SUP>87</SUP>Sr/<SUP>86</SUP>Sr) of the spring
and stream waters were characterized, as well as the stable isotope
compositions (δ<SUP>13</SUP>C, δ<SUP>15</SUP>N) and noble gas isotope
ratios of hydrothermal gases associated with spring waters. The results
show that thermal springs discharging on the carbonate platform are
close to saturation with calcite. PHREEQC modeling, together with
fluid geochemistry and temperature estimated from a combination of
geothermometers, indicate that Ca in these springs is inherited from
the alteration of the volcanic bedrock by aqueous fluids heated at
∼225 °C and enriched in magmatic mantle-derived CO<SUB>2</SUB>. Our
results clearly show that the main driver for the precipitation of
modern carbonates in Laguna Pastos Grandes is the deeply sourced
CO<SUB>2</SUB>, which boosts the alteration of volcanic rocks at depth.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Proxima Cen RV, FWHM and fluxes
(Suarez Mascareno+, 2020)
Authors: Suarez Mascareno, A.; Faria, J. P.; Figueira, P.; Lovis,
C.; Damasso, M.; Gonzalez Hernandez, J. I.; Rebolo, R.; Cristiano,
S.; Pepe, F.; Santos, N. C.; Zapatero Osorio, M. R.; Adibekyan, V.;
Hojjatpanah, S.; Sozzetti, A.; Murgas, F.; Abreu, M.; Affolter, M.;
Alibert, Y.; Aliverti, M.; Allart, R.; Allende Prieto, C.; Alves,
D.; Amate, M.; Avila, G.; Baldini, V.; Bandi, T.; Barros, S. C. C.;
Bianco, A.; Benz, W.; Bouchy, F.; Broeng, C.; Cabral, A.; Calderone,
G.; Cirami, R.; Coleho, J.; Conconi, P.; Coretti, I.; Cumani, C.;
Cupani, G.; D Odorico, V.; Deiries, S.; Delabre, B.; di Marcantonio,
P.; Dumusque, X.; Ehrenreich, D.; Fragoso, A.; Genolet, L.; Genoni,
M.; Genova Santos, R.; Hughes, I.; Iwert, O.; Kerber, F.; Knusdrtrup,
J.; Landoni, M.; Lavie, B.; Lillo-Box, J.; Lizon, J.; Lo Curto, G.;
Maire, C.; Manescau, A.; Martins, C. J. A. P.; Megevand, D.; Mehner,
A.; Micela, G.; Modigliani, A.; Molaro, P.; Monteiro, M. A.; Monteiro,
M. J. P. F. G.; Moschetti, M.; Mueller, E.; Nunes, N. J.; Oggioni,
L.; Oliveira, A.; Palle, E.; Pariani, G.; Pasquini, L.; Poretti E!,
.; Rasill, A. J. L.; Redaelli, E.; Riva, M.; Santana Tschudi, S.;
Santin, P.; Santos, P.; Segovia, A.; Sosnowska, D.; Sousa, S.; Snano,
P.; Tenegi, F.; Udry, S.; Zanutta, A.; Zerbi, F.
2020yCat..36390077S Altcode:
We obtained 67 individual spectra as part of the ESPRESSO GTO,
as part of programme ID 1102.C-744 (PI: F.Pepe). Measurements were
taken in ESPRESSO's 1UT high resolution (HR) mode with 15 minutes of
integration time. More information on the different observing modes
can be found on the ESO instrument page. ESPRESSO is equipped with its
own pipeline providing extracted and wavelength-calibrated spectra,
as well as RV measurements. The RV measurements are determined by a
Gaussian fit of the cross-correlation function (CCF) of the spectrum
with a binary mask computed from a stellar template. The mask was
created using an ESPRESSO spectrum of Proxima as a template. Lines were
identified through an automatic line-searching algorithm based on the
spectrum derivative. The pipeline, version 2.0.0, is fully available
to download from the ESO pipeline website. <P />In combination with
the ESPRESSO data we include the measurements taken between 2003 and
2017 with the High Accuracy Radial velocity Planet Searcher (HARPS)
spectrograph. These data where obtained by the Geneva/Grenoble survey
and the RedDots project, under programmes 072.C-0488, 082.C-0718,
183.C-0437, 191.C-0505, 096.C-0082, 099.C-0205, and 099.C-0880. This
dataset is comprised of 196 individual measurements that include
two high cadence campaigns in 2016 and 2017. The RVs were calculated
using the TERRA package and have been obtained from. In 2015 HARPS was
updated with new fibres, which improved its stability but also caused
an RV offset with respect to previous measurements. For this reason we
treat both HARPS datasets independently. The majority of the data were
obtained without simultaneous calibration, which limits the stability of
HARPS to a level of 1m/s. <P />Along with the previous data we include
the RVs taken with the Ultraviolet and Visual Echelle Spectrograph
(UVES) and analysed in Dmasso et al. 2020. This dataset consists of 77
nightly binned UVES RVs obtained between 2000 and 2007. The UVES data
were obtained in one of the early RV surveys for planets around M-dwarfs
under ESO programme IDs: 65.L-0428, 66.C-0446, 267.C-5700, 68.C-0415,
69.C-0722, 70.C-0044, 71.C-0498, 072.C-0495, 173.C-0606, and 078.C-0829
(PI: M. Kuerster). The data reduction and RV measurement is described in
Butler et al., 2019AJ....158..251B. Cat. J/AJ/158/251). The UVES data do
not include a measurement of the FWHM, as it is not easily available due
to calibration by the iodine gas absorption cell. <P />(3 data files).
---------------------------------------------------------
Title: Impact of SDSS Clustering Measurements on the Cosmological
Model
Authors: Mueller, E.; eBOSS Collaboration; Dawson, K.; Bautista, J.;
de Mattia, A.; Rossi, G.; Hou, J.; Zarrouk, P.; Percival, W.
2020AAS...23541307M Altcode:
In the past decades, understanding the cosmic expansion and growth of
structure of our Universe has been the primary focus of cosmological
research. Large scale structure measurements of BAO and RSD are crucial
to improve our knowledge of the underlying physical mechanisms that
govern our Universe as well as to test the predictions of the LCDM
(Lambda Cold Dark Matter) model, the standard cosmological model. In
this talk, I present the cosmological implications of the final BOSS
and eBOSS spectroscopic programs including constraints on dark energy
and massive neutrinos.
---------------------------------------------------------
Title: N-Body Simulations and Model Testing
Authors: Rossi, G.; Dawson, K.; Percival, W.; Bautista, J.; de Mattia,
A.; Hou, J.; Zarrouk, P.; Mueller, E.
2020AAS...23541304R Altcode:
Quantifying the systematic error budget in redshift space distortion
measurements from galaxy surveys is an essential step towards the
determination of unbiased estimates of the cosmic growth rate. We
developed a set of mock data challenges (including a blind series)
to simulate clustering studies with eBOSS Luminous Red Galaxies,
Emission Line Galaxies, and Quasars. The data challenge catalogs were
based on high-fidelity mocks constructed from state-of-the-art N-body
simulations such as the Outer Rim. In this talk, I will present results
from those mock challenges and I will quantify the systematic error
budget for the final growth estimates in eBOSS. I will also briefly
touch upon the novel series of EZmocks, critical to quantifying the
precision of the final eBOSS clustering results. Results from our
study have broader application, as similar mock-making techniques
and systematic corrections will be applied to DESI galaxy and quasar
clustering studies.
---------------------------------------------------------
Title: Introduction: the Extended Baryon Spectroscopic Survey
Authors: Dawson, K. S.; Percival, W.; Bautista, J.; Hou, J.; de Mattia,
A.; Mueller, E.; Myers, A.; Rossi, G.; Zarrouk, P.; Zhao, G.
2020AAS...23541301D Altcode:
The Extended Baryon Oscillation Spectroscopic Survey (eBOSS) concluded
observations of the cosmic distance scale and the growth of structure
in February, 2019. The full sample of galaxy surveys within the Sloan
Digital Sky Survey allows an exploration of Baryon Acoustic Oscillations
(BAO) and redshift-space distortions (RSD) out to redshifts z <
3.5. I will present an overview of the survey and observational
techniques as an introduction to the special session on final eBOSS
results.
---------------------------------------------------------
Title: Emission Line Galaxies as a Distinct Tracer
Authors: de Mattia, A.; Bautista, J.; Dawson, K.; Hou, J.; Mueller,
E.; Percival, W. J.; Rossi, G.; Zarrouk, P.; Zhao, G.
2020AAS...23541303D Altcode:
The Emission Line Galaxy (ELG) sample of the Extended Baryon Oscillation
Spectroscopic Survey (eBOSS) is one of the two largest ELG catalogs
to date with its 170,000 galaxies. Designed to probe galaxies at high
redshift (0.6 < z < 1.1) and at high density, this program
is a pathfinder to next generation spectroscopic surveys such as
the Dark Energy Spectroscopic Instrument (DESI), which will probe
100 times more galaxies. In this talk, I will explain how the ELG
photometric selection impacts the clustering signal and present the
various analysis techniques developed to ensure robust cosmological
measurements. To conclude, I will present the best estimates derived
for the growth rate of structure and lessons for future galaxy surveys.
---------------------------------------------------------
Title: GRAVITY and the Galactic Centre
Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler,
T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.;
Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy,
M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast,
R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti,
A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet,
É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.;
Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit,
W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert,
G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.;
Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.;
Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.;
Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.;
Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.;
Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.;
Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler,
S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.;
Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum,
L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.;
Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.;
Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki,
M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère,
V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen,
R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.;
Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière,
P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.;
Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro,
J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.;
Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc,
T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto,
A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray,
T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.;
Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer,
S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.;
Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub,
O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.;
Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.;
van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.;
Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann,
F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez,
J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G.
2019Msngr.178...26G Altcode:
On a clear night, our home galaxy, the Milky Way, is visible as a
starry ribbon across the sky. Its core is located in the constellation
of Sagittarius, approximately where the bright glow is interrupted
by the darkest dust filaments. There, hidden, lies a massive black
hole. To peer through the obscuring clouds and see the stars and gas
near the black hole we use GRAVITY. The main GRAVITY results are the
detection of gra- vitational redshift, the most precise mass- distance
measurement, the test of the equivalence principle, and the detection
of orbital motion near the black hole.
---------------------------------------------------------
Title: An Image of the Dust Sublimation Region in the Nucleus of
NGC 1068
Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler,
T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.;
Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy,
M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast,
R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti,
A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet,
É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.;
Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit,
W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert,
G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.;
Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.;
Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.;
Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.;
Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.;
Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.;
Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler,
S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.;
Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum,
L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.;
Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.;
Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki,
M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère,
V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen,
R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.;
Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière,
P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.;
Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro,
J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.;
Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc,
T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto,
A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray,
T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.;
Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer,
S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.;
Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub,
O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.;
Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.;
van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.;
Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann,
F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez,
J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G.
2019Msngr.178...24G Altcode:
The superb resolution of the Very Large Telescope Interferometer
(VLTI) and the unrivalled sensitivity of GRAVITY have allowed us to
reconstruct the first detailed image of the dust sublimation region in
an active galaxy. In the nearby archetypal Seyfert 2 galaxy NGC 1068,
the 2 µm continuum emission traces a highly inclined thin ring-like
structure with a radius of 0.24 pc. The observed morphology challenges
the picture of a geometrically and optically thick torus.
---------------------------------------------------------
Title: Spatially Resolved Accretion-Ejection in Compact Binaries
with GRAVITY
Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler,
T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.;
Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy,
M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast,
R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti,
A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet,
É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.;
Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit,
W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert,
G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.;
Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.;
Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.;
Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.;
Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.;
Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.;
Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler,
S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.;
Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum,
L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.;
Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.;
Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki,
M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère,
V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen,
R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.;
Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière,
P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.;
Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro,
J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.;
Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc,
T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto,
A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray,
T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.;
Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer,
S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.;
Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub,
O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.;
Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.;
van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.;
Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann,
F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez,
J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G.
2019Msngr.178...29G Altcode:
The GRAVITY instrument at the Very Large Telescope Interferometer has
led to the first spatially resolved observations of X-ray binaries at
scales comparable to the binary orbit, providing unprecedented spatial
information on their accretion-ejection mechanisms. In particular,
observations of the hypercritical accretor SS433 have revealed a
variety of spatial structures at the heart of this exotic microquasar,
including bipolar outflows, super-Keplerian equatorial outflows and
extended baryonic jets photoionised by collimated ultraviolet radiation.
---------------------------------------------------------
Title: Hunting Exoplanets with Single-Mode Optical Interferometry
Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler,
T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.;
Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy,
M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast,
R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti,
A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet,
É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.;
Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit,
W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert,
G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.;
Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.;
Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.;
Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.;
Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.;
Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.;
Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler,
S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.;
Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum,
L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.;
Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.;
Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki,
M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère,
V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen,
R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.;
Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière,
P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.;
Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro,
J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.;
Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc,
T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto,
A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray,
T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.;
Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer,
S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.;
Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub,
O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.;
Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.;
van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.;
Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann,
F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez,
J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G.
2019Msngr.178...47G Altcode:
The GRAVITY instrument was primarily conceived for imaging and
astrometry of the Galactic centre. However, its sensitivity and
astrometric capabilities have also enabled interferometry to reach
a new domain of astrophysics: exoplanetology. In March 2019, the
GRAVITY collaboration published the first spectrum and astrometry of an
exoplanet obtained by optical interferometry. In this article, we show
how this observation is paving the way to even more exciting discoveries
— finding new planets, and characterising their atmospheres.
---------------------------------------------------------
Title: Spatially Resolving the Inner Gaseous Disc of the Herbig Star
51 Oph through its CO Ro-vibration Emission
Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler,
T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.;
Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy,
M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast,
R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti,
A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet,
É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.;
Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit,
W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert,
G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.;
Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.;
Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.;
Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.;
Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.;
Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.;
Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler,
S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.;
Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum,
L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.;
Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.;
Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki,
M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère,
V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen,
R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.;
Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière,
P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.;
Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro,
J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.;
Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc,
T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto,
A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray,
T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.;
Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer,
S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.;
Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub,
O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.;
Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.;
van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.;
Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann,
F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez,
J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G.
2019Msngr.178...40G Altcode:
Near-infrared interferometry gives us the opportunity to
spatially resolve the circumstellar environment of young stars at
sub-astronomical-unit (au) scales, which a standalone telescope could
not reach. In particular, the sensitivity of GRAVITY on the VLTI allows
us to spatially resolve the CO overtone emission at 2.3 microns. In
this article, we present a new method of using the model of the CO
spectrum to reconstruct the differential phase signal and extract the
geometry and size of the emitting region.
---------------------------------------------------------
Title: Spatially Resolving the Quasar Broad Emission Line Region
Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler,
T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.;
Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy,
M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast,
R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti,
A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet,
É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.;
Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit,
W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert,
G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.;
Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.;
Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.;
Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.;
Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.;
Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.;
Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler,
S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.;
Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum,
L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.;
Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.;
Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki,
M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère,
V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen,
R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.;
Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière,
P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.;
Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro,
J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.;
Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc,
T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto,
A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray,
T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.;
Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer,
S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.;
Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub,
O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.;
Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.;
van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.;
Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann,
F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez,
J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G.
2019Msngr.178...20A Altcode:
The angular resolution of the Very Large Telescope Interferometer
(VLTI) and the excellent sensitivity of GRAVITY have led to the
first detection of spatially resolved kinematics of high velocity
atomic gas near an accreting super- massive black hole, revealing
rotation on sub-parsec scales in the quasar 3C 273 at a distance of
550 Mpc. The observations can be explained as the result of circular
orbits in a thick disc configuration around a 300 million solar mass
black hole. Within an ongoing Large Programme, this capability will
be used to study the kinematics of atomic gas and its relation to hot
dust in a sample of quasars and Seyfert galaxies. We will measure a
new radius-luminosity relation from spatially resolved data and test
the current methods used to measure black hole mass in large surveys.
---------------------------------------------------------
Title: Multiple Star Systems in the Orion Nebula
Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler,
T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.;
Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy,
M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast,
R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti,
A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet,
É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.;
Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit,
W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert,
G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.;
Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.;
Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.;
Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.;
Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.;
Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.;
Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler,
S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.;
Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum,
L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.;
Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.;
Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki,
M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère,
V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen,
R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.;
Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière,
P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.;
Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro,
J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.;
Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc,
T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto,
A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray,
T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.;
Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer,
S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.;
Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub,
O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.;
Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.;
van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.;
Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann,
F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez,
J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G.
2019Msngr.178...36G Altcode:
GRAVITY observations reveal that most massive stars in the
Orion Trapezium cluster live in multiple systems. Our deep,
milliarcsecond-resolution interferometry fills the gap at 1-100
astronomical units (au), which is not accessible to traditional imaging
and spectroscopy, but is crucial to uncovering the mystery of high-mass
star formation.The new observations find a significantly higher
companion fraction than earlier studies of mostly OB associations. The
observed distribution of mass ratios declines steeply with mass and
follows a Salpeter power-law initial mass function. The observations
therefore exclude stellar mergers as the dominant formation mechanism
for massive stars in Orion.
---------------------------------------------------------
Title: Images at the Highest Angular Resolution with GRAVITY: The
Case of η Carinae
Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler,
T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.;
Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy,
M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast,
R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti,
A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet,
É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.;
Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit,
W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert,
G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.;
Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.;
Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.;
Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.;
Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.;
Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.;
Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler,
S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.;
Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum,
L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.;
Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.;
Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki,
M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère,
V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen,
R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.;
Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière,
P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.;
Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro,
J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.;
Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc,
T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto,
A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray,
T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.;
Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer,
S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.;
Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub,
O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.;
Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.;
van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.;
Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann,
F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez,
J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G.
2019Msngr.178...31G Altcode:
The main goal of an interferometer is to probe the physics of
astronomical objects at the highest possible angular resolution. The
most intuitive way of doing this is by reconstructing images from the
interferometric data. GRAVITY at the Very Large Telescope Interferometer
(VLTI) has proven to be a fantastic instrument in this endeavour. In
this article, we describe the reconstruction of the wind-wind collision
cavity of the massive binary η Car with GRAVITY across two spectral
lines: HeI and Brγ.
---------------------------------------------------------
Title: Probing the Discs of Herbig Ae/Be Stars at Terrestrial Orbits
Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler,
T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.;
Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy,
M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast,
R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti,
A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet,
É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.;
Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit,
W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert,
G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.;
Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.;
Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.;
Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.;
Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.;
Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.;
Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler,
S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.;
Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum,
L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.;
Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.;
Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki,
M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère,
V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen,
R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.;
Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière,
P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.;
Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro,
J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.;
Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc,
T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto,
A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray,
T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.;
Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer,
S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.;
Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub,
O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.;
Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.;
van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.;
Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann,
F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez,
J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G.
2019Msngr.178...38G Altcode:
More than 4000 exoplanets are known to date in systems that differ
greatly from our Solar System. In particular, inner exoplanets tend
to follow orbits around their parent star that are much more compact
than that of Earth. These systems are also extremely diverse, covering
a range of intrinsic properties. Studying the main physi- cal processes
at play in the innermost regions of the protoplanetary discs is crucial
to understanding how these planets form and migrate so close to their
host. With GRAVITY, we focused on the study of near-infrared emission
of a sample of young intermediate- mass stars, the Herbig Ae/Be stars.
---------------------------------------------------------
Title: Vertical shear mixing in stellar radiative zones
Authors: Prat, V.; Guilet, J.; Vialler, M.; Müller, E.
2019EAS....82..167P Altcode:
Jean-Paul Zahn's formalism for vertical shear mixing is used in several
stellar evolution codes, but the physics of the shear instability in
stellar radiative zones is still not completely understood. Over the
last few years, numerical simulations have provided new constraints on
the shear instability, including the effect of thermal diffusion and
chemical stratification. We present here new simulations that show
the effect of viscosity on the vertical turbulent transport due to
the shear instability.
---------------------------------------------------------
Title: Gravitational waves from 3D core-collapse supernova models:
The impact of moderate progenitor rotation
Authors: Andresen, H.; Müller, E.; Janka, H. -Th; Summa, A.; Gill,
K.; Zanolin, M.
2019MNRAS.486.2238A Altcode: 2018arXiv181007638A; 2019MNRAS.tmp..977A
We present predictions for the gravitational wave (GW) emission of 3D
supernova simulations performed for a 15 solar-mass progenitor with the
PROMETHEUS-VERTEX code using energy-dependent, three-flavour neutrino
transport. The progenitor adopted from stellar evolution calculations
including magnetic fields had a fairly low specific angular momentum
(j<SUB>Fe</SUB> ≲ 10<SUP>15</SUP> cm<SUP>2</SUP> s<SUP>-1</SUP>)
in the iron core (central angular velocity Ω<SUB>Fe,c</SUB> ∼
0.2 rad s<SUP>-1</SUP>), which we compared to simulations without
rotation and with artificially enhanced rotation (j<SUB>Fe</SUB> ≲
2 × 10<SUP>16</SUP> cm<SUP>2</SUP> s<SUP>-1</SUP>; Ω<SUB>Fe,c</SUB>
∼ 0.5 rad s<SUP>-1</SUP>). Our results confirm that the time-domain
GW signals of SNe are stochastic, but possess deterministic components
with characteristic patterns at low frequencies (≲200 Hz), caused by
mass motions due to the standing accretion shock instability (SASI),
and at high frequencies, associated with gravity-mode oscillations
in the surface layer of the proto-neutron star (PNS). Non-radial
mass motions in the post-shock layer as well as PNS convection are
important triggers of GW emission, whose amplitude scales with the
power of the hydrodynamic flows. There is no monotonic increase of
the GW amplitude with rotation, but a clear correlation with the
strength of SASI activity. Our slowly rotating model is a fainter GW
emitter than the non-rotating model because of weaker SASI activity
and damped convection in the post-shock layer and PNS. In contrast,
the faster rotating model exhibits a powerful SASI spiral mode during
its transition to explosion, producing the highest GW amplitudes with
a distinctive drift of the low-frequency emission peak from ∼80-100
to ∼40-50 Hz. This migration signifies shock expansion, whereas
non-exploding models are discriminated by the opposite trend.
---------------------------------------------------------
Title: Titanium hidden in dust
Authors: Iyudin, A. F.; Müller, E.; Obergaulinger, M.
2019MNRAS.485.3288I Altcode: 2019MNRAS.tmp..424I; 2019arXiv190202249I
Cassiopeia A, one of the most intriguing Galactic supernova remnants,
has been a target of many observational efforts including most recent
observations by Atacama Large Millimeter/submillimeter Array (ALMA),
Hubble, Herschel, Spitzer, NuSTAR, INTEGRAL, and other observatories. We
use recent gamma-ray lines observations of the radioactive products
of Cas A supernova explosive nucleosynthesis and spectral energy
densities derived for Cas A at infrared wavelengths to speculate
about the possibility of radioactive {}^{44}_{}Ti being locked into
large dust grains. This suggestion is also supported by the possible
observation of a pre-supernova outburst about 80 yr before the
actual Cas A supernova explosion in 1671 AD by Italian astronomer
G. D. Cassini. The plausibility of such a scenario is discussed
also with reference to recent supernovae, and to the contribution of
core-collapse supernovae to the overall dust production in the Galaxy.
---------------------------------------------------------
Title: Three-dimensional mixing and light curves: constraints on
the progenitor of supernova 1987A
Authors: Utrobin, V. P.; Wongwathanarat, A.; Janka, H. -Th.; Müller,
E.; Ertl, T.; Woosley, S. E.
2019A&A...624A.116U Altcode: 2018arXiv181211083U
With the same method as used previously, we investigate neutrino-driven
explosions of a larger sample of blue supergiant models. The
blue supergiants were evolved as single-star progenitors. The
larger sample includes three new presupernova stars. The results
are compared with light-curve observations of the peculiar type
IIP supernova 1987A (SN 1987A). The explosions were modeled
in 3D with the neutrino-hydrodynamics code PROMETHEUS-HOTB, and
light-curve calculations were performed in spherical symmetry with
the radiation-hydrodynamics code CRAB, starting at a stage of nearly
homologous expansion. Our results confirm the basic findings of the
previous work: 3D neutrino-driven explosions with SN 1987A-like energies
synthesize an amount of <SUP>56</SUP>Ni that is consistent with the
radioactive tail of the light curve. Moreover, the models mix hydrogen
inward to minimum velocities below 400 km s<SUP>-1</SUP> as required
by spectral observations and a 3D analysis of molecular hydrogen in SN
1987A. Hydrodynamic simulations with the new progenitor models, which
possess smaller radii than the older ones, show much better agreement
between calculated and observed light curves in the initial luminosity
peak and during the first 20 days. A set of explosions with similar
energies demonstrated that a high growth factor of Rayleigh-Taylor
instabilities at the (C+O)/He composition interface combined with a
weak interaction of fast Rayleigh-Taylor plumes, where the reverse
shock occurs below the He/H interface, provides a sufficient condition
for efficient outward mixing of <SUP>56</SUP>Ni into the hydrogen
envelope. This condition is realized to the required extent only in one
of the older stellar models, which yielded a maximum velocity of around
3000 km s<SUP>-1</SUP> for the bulk of ejected <SUP>56</SUP>Ni, but
failed to reproduce the helium-core mass of 6 M<SUB>⊙</SUB> inferred
from the absolute luminosity of the presupernova star. We conclude that
none of the single-star progenitor models proposed for SN 1987A to
date satisfies all constraints set by observations. <P />Data of the
presupernova models for blue supergiants, the angle-averaged profiles
of the 3D explosion models, and the corresponding bolometric light
curves are available in electronic form at the CDS via anonymous ftp <A
href="http://cdsarc.u-strasbg.fr/">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A116">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A116</A>
---------------------------------------------------------
Title: VizieR Online Data Catalog: Constraints on the progenitor of
SN 1987A (Utrobin+, 2019)
Authors: Utrobin, V. P.; Wongwathanarat, A.; Janka, H. -T.; Mueller,
E.; Ertl, T.; Woosley, S. E.
2019yCat..36240116U Altcode:
7 presupernova models for blue supergiants B15, W16, W18, W18r,
W18x, W20, and N20 were used as initial data for 3D simulations of
neutrino-driven explosions and the corresponding hydrodynamic models
B15-2, W16-3, W18, W18r-2, W18x-2, W20, and N20-P with SN 1987A-like
explosion energies were calculated. 3D models B15-2, W16-3, W18,
W18r-2, W18x-2, W20, and N20-P were mapped to spherically symmetric
configurations at a stage of almost homologous expansion: 61218.22s,
88487.02s, 55204.19s, 89773.06s, 89134.01s, 61243.24s, and 56861.61s,
respectively. These 1D configurations were used as initial data for
simulations of bolometric light curves. <P />(28 data files).
---------------------------------------------------------
Title: ePESSTO Transient Classification Report for 2018-12-03
Authors: Pursiainen; M; Castro; N; Gutierrez; P, C.; Muller; T;
Yaron, O.
2018TNSCR2051....1P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: GRAVITY chromatic imaging of η Car's core. Milliarcsecond
resolution imaging of the wind-wind collision zone (Brγ, He I)
Authors: GRAVITY Collaboration; Sanchez-Bermudez, J.; Weigelt,
G.; Bestenlehner, J. M.; Kervella, P.; Brandner, W.; Henning, Th.;
Müller, A.; Perrin, G.; Pott, J. -U.; Schöller, M.; van Boekel, R.;
Abuter, R.; Accardo, M.; Amorim, A.; Anugu, N.; Ávila, G.; Benisty,
M.; Berger, J. P.; Blind, N.; Bonnet, H.; Bourget, P.; Brast, R.;
Buron, A.; Cantalloube, F.; Caratti O Garatti, A.; Cassaing, F.;
Chapron, F.; Choquet, E.; Clénet, Y.; Collin, C.; Coudé Du Foresto,
V.; de Wit, W.; de Zeeuw, T.; Deen, C.; Delplancke-Ströbele, F.;
Dembet, R.; Derie, F.; Dexter, J.; Duvert, G.; Ebert, M.; Eckart,
A.; Eisenhauer, F.; Esselborn, M.; Fédou, P.; Garcia, P. J. V.;
Garcia Dabo, C. E.; Garcia Lopez, R.; Gao, F.; Gendron, E.; Genzel,
R.; Gillessen, S.; Haubois, X.; Haug, M.; Haussmann, F.; Hippler,
S.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.; Hummel, C. A.;
Jakob, G.; Jochum, L.; Jocou, L.; Karl, M.; Kaufer, A.; Kellner, S.;
Kendrew, S.; Kern, L.; Kiekebusch, M.; Klein, R.; Kolb, J.; Kulas, M.;
Lacour, S.; Lapeyrère, V.; Lazareff, B.; Le Bouquin, J. -B.; Léna,
P.; Lenzen, R.; Lévêque, S.; Lippa, M.; Magnard, Y.; Mehrgan, L.;
Mellein, M.; Mérand, A.; Moreno-Ventas, J.; Moulin, T.; Müller,
E.; Müller, F.; Neumann, U.; Oberti, S.; Ott, T.; Pallanca, L.;
Panduro, J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.;
Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Duc, T. P.; Plewa, P. M.;
Popovic, D.; Rabien, S.; Ramirez, A.; Ramos, J.; Rau, C.; Riquelme,
M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rosales, A.; Rousset, G.;
Scheithauer, S.; Schuhler, N.; Spyromilio, J.; Straub, O.; Straubmeier,
C.; Sturm, E.; Suarez, M.; Tristram, K. R. W.; Ventura, N.; Vincent,
F.; Waisberg, I.; Wank, I.; Widmann, F.; Wieprecht, E.; Wiest, M.;
Wiezorrek, E.; Wittkowski, M.; Woillez, J.; Wolff, B.; Yazici, S.;
Ziegler, D.; Zins, G.
2018A&A...618A.125G Altcode: 2018arXiv180802141G
Context. η Car is one of the most intriguing luminous blue variables in
the Galaxy. Observations and models of the X-ray, ultraviolet, optical,
and infrared emission suggest a central binary in a highly eccentric
orbit with a 5.54 yr period residing in its core. 2D and 3D radiative
transfer and hydrodynamic simulations predict a primary with a dense and
slow stellar wind that interacts with the faster and lower density wind
of the secondary. The wind-wind collision scenario suggests that the
secondary's wind penetrates the primary's wind creating a low-density
cavity in it, with dense walls where the two winds interact. However,
the morphology of the cavity and its physical properties are not yet
fully constrained. <BR /> Aims: We aim to trace the inner ∼5-50
au structure of η Car's wind-wind interaction, as seen through Brγ
and, for the first time, through the He I 2s-2p line. <BR /> Methods:
We have used spectro-interferometric observations with the K-band
beam-combiner GRAVITY at the VLTI. The analyses of the data include
(i) parametrical model-fitting to the interferometric observables,
(ii) a CMFGEN model of the source's spectrum, and (iii) interferometric
image reconstruction. <BR /> Results: Our geometrical modeling of the
continuum data allows us to estimate its FWHM angular size close to
2 mas and an elongation ratio ɛ = 1.06 ± 0.05 over a PA = 130° ±
20°. Our CMFGEN modeling of the spectrum helped us to confirm that
the role of the secondary should be taken into account to properly
reproduce the observed Brγ and He I lines. Chromatic images across the
Brγ line reveal a southeast arc-like feature, possibly associated to
the hot post-shocked winds flowing along the cavity wall. The images
of the He I 2s-2p line served to constrain the 20 mas (∼50 au)
structure of the line-emitting region. The observed morphology of He
I suggests that the secondary is responsible for the ionized material
that produces the line profile. Both the Brγ and the He I 2s-2p maps
are consistent with previous hydrodynamical models of the colliding
wind scenario. Future dedicated simulations together with an extensive
interferometric campaign are necessary to refine our constraints on
the wind and stellar parameters of the binary, which finally will help
us predict the evolutionary path of η Car.
---------------------------------------------------------
Title: Papaloizou-Pringle instability suppression by the
magnetorotational instability in relativistic accretion discs
Authors: Bugli, M.; Guilet, J.; Müller, E.; Del Zanna, L.;
Bucciantini, N.; Montero, P. J.
2018MNRAS.475..108B Altcode: 2017arXiv170701860B
Geometrically thick tori with constant specific angular momentum
have been widely used in the last decades to construct numerical
models of accretion flows on to black holes. Such discs are prone
to a global non-axisymmetric hydrodynamic instability, known as
Papaloizou-Pringle instability (PPI), which can redistribute angular
momentum and also lead to an emission of gravitational waves. It is,
however, not clear yet how the development of the PPI is affected by the
presence of a magnetic field and by the concurrent development of the
magnetorotational instability (MRI). We present a numerical analysis
using three-dimensional GRMHD simulations of the interplay between
the PPI and the MRI considering, for the first time, an analytical
magnetized equilibrium solution as initial condition. In the purely
hydrodynamic case, the PPI selects as expected the large-scale m =
1 azimuthal mode as the fastest growing and non-linearly dominant
mode. However, when the torus is threaded by a weak toroidal
magnetic field, the development of the MRI leads to the suppression
of large-scale modes and redistributes power across smaller scales. If
the system starts with a significantly excited m = 1 mode, the PPI can
be dominant in a transient phase, before being ultimately quenched by
the MRI. Such dynamics may well be important in compact star mergers
and tidal disruption events.
---------------------------------------------------------
Title: Emission line models for the lowest mass core-collapse
supernovae - I. Case study of a 9 M<SUB>⊙</SUB> one-dimensional
neutrino-driven explosion
Authors: Jerkstrand, A.; Ertl, T.; Janka, H. -T.; Müller, E.;
Sukhbold, T.; Woosley, S. E.
2018MNRAS.475..277J Altcode: 2017arXiv171004508J
A large fraction of core-collapse supernovae (CCSNe), 30-50 per
cent, are expected to originate from the low-mass end of progenitors
with M<SUB>ZAMS</SUB> = 8-12 M<SUB>⊙</SUB>. However, degeneracy
effects make stellar evolution modelling of such stars challenging,
and few predictions for their supernova light curves and spectra have
been presented. Here, we calculate synthetic nebular spectra of a 9
M<SUB>⊙</SUB> Fe CCSN model exploded with the neutrino mechanism. The
model predicts emission lines with FWHM ∼ 1000 km s<SUP>-1</SUP>,
including signatures from each deep layer in the metal core. We compare
this model to the observations of the three subluminous IIP SNe with
published nebular spectra; SN 1997D, SN 2005cs and SN 2008bk. The
predictions of both line profiles and luminosities are in good agreement
with SN 1997D and SN 2008bk. The close fit of a model with no tuning
parameters provides strong evidence for an association of these objects
with low-mass Fe CCSNe. For SN 2005cs, the interpretation is less clear,
as the observational coverage ended before key diagnostic lines from
the core had emerged. We perform a parametrized study of the amount
of explosively made stable nickel, and find that none of these three
SNe show the high <SUP>58</SUP>Ni/<SUP>56</SUP>Ni ratio predicted
by current models of electron capture SNe (ECSNe) and ECSN-like
explosions. Combined with clear detection of lines from O and He shell
material, these SNe rather originate from Fe core progenitors. We argue
that the outcome of self-consistent explosion simulations of low-mass
stars, which gives fits to many key observables, strongly suggests that
the class of subluminous Type IIP SNe is the observational counterpart
of the lowest mass CCSNe.
---------------------------------------------------------
Title: Isolated massive star formation . Myth or reality?
Authors: Gouliermis, D. A.; Stephens, I. W.; Looney, L. W.; Gruendl,
R. A.; Chu, Y. -H.; Weisz, D. R.; Seale, J. P.; Chen, C. -H. R.;
Wong, T.; Hughes, A.; Pineda, J. L.; Ott, J.; Muller, E.
2018MmSAI..89...57G Altcode:
High-mass stars apparently formed in the field challenge the
paradigm of clustered star formation. To understand the conditions
that favor isolated massive star formation, we employed the Hubble
Space Telescope to observe the seven most isolated massive YSOs in the
LMC. Our investigation shows that while they are quite remote from any
star-forming region, these YSOs are not isolated at all. HST revealed a
plethora of Pre-Main-Sequence stars, forming compact clusters around the
YSOs, and sparsely distributed across the observed regions. Contrary to
previous studies, these observations suggest that high-mass stars may
not be able to form in clusters smaller than 100 M_⊙, and that the
lack of isolation is at odds with random sampling of the stellar IMF.
---------------------------------------------------------
Title: Magneto-elastic oscillations modulating the emission of
magnetars
Authors: Gabler, M.; Cerdá-Durán, P.; Mate, A.; Stergioulas, N.;
Font, J. A.; Müller, E.
2017AN....338.1105G Altcode: 2017arXiv170906806G
Magneto-elastic oscillations of neutron stars are believed to explain
the observed quasi-periodic oscillations (QPOs) in the decaying tail of
the giant flares of highly magnetized neutron stars (magnetars). Strong
efforts by theoretical modeling from different groups have increased
our understanding of this phenomenon significantly. Here we discuss
some constraints on the matter in neutron stars that arise if
the interpretation of the observations in terms of superfluid
magneto-elastic oscillations is correct. To explain the observed
modulation of the light curve of the giant flare, we describe a model
that allows the QPOs to couple to the stellar exterior through the
magnetic field. In this magnetosphere, the shaking magnetic field
induces currents that provide scattering targets for resonant cyclotron
scattering of photons, which is calculated with a Monte Carlo approach
and coupled to a code that calculates the momentum distribution of the
charge carriers as a one-dimensional accelerator problem. We show first
results of a simplified, but self-consistent momentum distribution,
that is a water-bag distribution, and the corresponding spectra.
---------------------------------------------------------
Title: The wind and the magnetospheric accretion onto the T Tauri
star S Coronae Australis at sub-au resolution
Authors: GRAVITY Collaboration; Garcia Lopez, R.; Perraut, K.; Caratti
O Garatti, A.; Lazareff, B.; Sanchez-Bermudez, J.; Benisty, M.;
Dougados, C.; Labadie, L.; Brandner, W.; Garcia, P. J. V.; Henning,
Th.; Ray, T. P.; Abuter, R.; Amorim, A.; Anugu, N.; Berger, J. P.;
Bonnet, H.; Buron, A.; Caselli, P.; Clénet, Y.; Coudé Du Foresto,
V.; de Wit, W.; Deen, C.; Delplancke-Ströbele, F.; Dexter, J.;
Eckart, A.; Eisenhauer, F.; Garcia Dabo, C. E.; Gendron, E.; Genzel,
R.; Gillessen, S.; Haubois, X.; Haug, M.; Haussmann, F.; Hippler,
S.; Hubert, Z.; Hummel, C. A.; Horrobin, M.; Jocou, L.; Kellner, S.;
Kervella, P.; Kulas, M.; Kolb, J.; Lacour, S.; Le Bouquin, J. -B.;
Léna, P.; Lippa, M.; Mérand, A.; Müller, E.; Ott, T.; Panduro, J.;
Paumard, T.; Perrin, G.; Pfuhl, O.; Ramirez, A.; Rau, C.; Rohloff,
R. -R.; Rousset, G.; Scheithauer, S.; Schöller, M.; Straubmeier,
C.; Sturm, E.; Thi, W. F.; van Dishoeck, E.; Vincent, F.; Waisberg,
I.; Wank, I.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Woillez, J.;
Yazici, S.; Zins, G.
2017A&A...608A..78G Altcode: 2017arXiv170901348G
<BR /> Aims: To investigate the inner regions of protoplanetary
discs, we performed near-infrared interferometric observations
of the classical T Tauri binary system S CrA. <BR /> Methods: We
present the first VLTI-GRAVITY high spectral resolution (R ~ 4000)
observations of a classical T Tauri binary, S CrA (composed of S
CrA N and S CrA S and separated by ~1.̋4), combining the four 8m
telescopes in dual-field mode. <BR /> Results: Our observations in
the near-infrared K-band continuum reveal a disc around each binary
component, with similar half-flux radii of about 0.1 au at d ~ 130 pc,
inclinations (i = 28 ± 3° and i = 22 ± 6°), and position angles (PA
= 0°± 6° and PA = -2°± 12°), suggesting that they formed from the
fragmentation of a common disc. The S CrA N spectrum shows bright He I
and Brγ line emission exhibiting inverse P Cygni profiles, typically
associated with infalling gas. The continuum-compensated Brγ line
visibilities of S CrA N show the presence of a compact Brγ emitting
region whose radius is about ~0.06 au, which is twice as big as the
truncation radius. This component is mostly tracing a wind. Moreover,
a slight radius change between the blue- and red-shifted Brγ line
components is marginally detected. <BR /> Conclusions: The presence
of an inverse P Cygni profile in the He I and Brγ lines, along with
the tentative detection of a slightly larger size of the blue-shifted
Brγ line component, hint at the simultaneous presence of a wind and
magnetospheric accretion in S CrA N.
---------------------------------------------------------
Title: Light-curve Analysis of Ordinary Type IIP Supernovae Based
on Neutrino-driven Explosion Simulations in Three Dimensions
Authors: Utrobin, V. P.; Wongwathanarat, A.; Janka, H. -Th.;
Müller, E.
2017ApJ...846...37U Altcode: 2017arXiv170403800U
Type II-plateau supernovae (SNe IIP) are the most numerous subclass
of core-collapse SNe originating from massive stars. In the framework
of the neutrino-driven explosion mechanism, we study the properties
of the SN outburst for a red supergiant progenitor model and compare
the corresponding light curves with observations of the ordinary Type
IIP SN 1999em. Three-dimensional (3D) simulations of (parametrically
triggered) neutrino-driven explosions are performed with the (explicit,
finite-volume, Eulerian, multifluid hydrodynamics) code Prometheus,
using a presupernova model of a 15 M <SUB>⊙</SUB> star as initial
data. On approaching homologous expansion, the hydrodynamic and
composition variables of the 3D models are mapped to a spherically
symmetric configuration, and the simulations are continued with
the (implicit, Lagrangian, radiation hydrodynamics) code Crab to
follow the evolution of the blast wave during the SN outburst. Our 3D
neutrino-driven explosion model with an explosion energy of about 0.5×
{10}<SUP>51</SUP> erg produces <SUP>56</SUP>Ni in rough agreement with
the amount deduced from fitting the radioactively powered light-curve
tail of SN 1999em. The considered presupernova model, 3D explosion
simulations, and light-curve calculations can explain the basic
observational features of SN 1999em, except for those connected
to the presupernova structure of the outer stellar layers. Our 3D
simulations show that the distribution of <SUP>56</SUP>Ni-rich matter
in velocity space is asymmetric with a strong dipole component that is
consistent with the observations of SN 1999em. The monotonic decline
in luminosity from the plateau to the radioactive tail in ordinary
SNe IIP is a manifestation of the intense turbulent mixing at the He/H
composition interface.
---------------------------------------------------------
Title: VizieR Online Data Catalog: AzTEC/ASTE survey at 1.1mm toward
the SMC (Takekoshi+, 2017)
Authors: Takekoshi, T.; Minamidani, T.; Komugi, S.; Kohno, K.; Tosaki,
T.; Sorai, K.; Muller, E.; Mizuno, N.; Kawamura, A.; Onishi, T.; Fukui,
Y.; Ezawa, H.; Oshima, T.; Scott, K. S.; Austermann, J. E.; Matsuo,
H.; Aretxaga, I.; Hughes, D. H.; Kawabe, R.; Wilson, G. W.; Yun, M. S.
2017yCat..18350055T Altcode:
Continuum observations at 1.1mm toward the SMC were conducted with the
AzTEC instrument installed on the ASTE telescope in the Atacama desert,
Chile. The angular resolution is 28" at FWHM. The observations covered
a total of a 4.5deg<SUP>2</SUP> field of the SMC by connecting four
patches of scans that are denominated as southwest (SW), northeast
(NE), Wing, and N88, as shown in Figure 1. Observations were performed
from 2008 October 7 to December 26. <P />(5 data files).
---------------------------------------------------------
Title: Submilliarcsecond Optical Interferometry of the High-mass
X-Ray Binary BP Cru with VLTI/GRAVITY
Authors: Waisberg, I.; Dexter, J.; Pfuhl, O.; Abuter, R.; Amorim,
A.; Anugu, N.; Berger, J. P.; Blind, N.; Bonnet, H.; Brandner, W.;
Buron, A.; Clénet, Y.; de Wit, W.; Deen, C.; Delplancke-Ströbele, F.;
Dembet, R.; Duvert, G.; Eckart, A.; Eisenhauer, F.; Fédou, P.; Finger,
G.; Garcia, P.; Garcia Lopez, R.; Gendron, E.; Genzel, R.; Gillessen,
S.; Haubois, X.; Haug, M.; Haussmann, F.; Henning, Th.; Hippler, S.;
Horrobin, M.; Hubert, Z.; Jochum, L.; Jocou, L.; Kervella, P.; Kok, Y.;
Kulas, M.; Lacour, S.; Lapeyrère, V.; Le Bouquin, J. -B.; Léna, P.;
Lippa, M.; Mérand, A.; Müller, E.; Ott, T.; Pallanca, L.; Panduro,
J.; Paumard, T.; Perraut, K.; Perrin, G.; Rabien, S.; Ramírez, A.;
Ramos, J.; Rau, C.; Rohloff, R. -R.; Rousset, G.; Sanchez-Bermudez, J.;
Scheithauer, S.; Schöller, M.; Straubmeier, C.; Sturm, E.; Vincent,
F.; Wank, I.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski,
M.; Woillez, J.; Yazici, S.; GRAVITY Collaboration
2017ApJ...844...72W Altcode: 2017arXiv170502351G
We observe the high-mass X-ray binary (HMXB) BP Cru using interferometry
in the near-infrared K band with VLTI/GRAVITY. Continuum visibilities
are at most partially resolved, consistent with the predicted size of
the hypergiant. Differential visibility amplitude ({{Δ }}| V| ∼ 5 %
) and phase ({{Δ }}φ ∼ 2^\circ ) signatures are observed across
the He I 2.059 μ {{m}} and Brγ lines, the latter seen strongly in
emission, unusual for the donor star’s spectral type. For a baseline
B∼ 100 m, the differential phase rms ∼ 0\buildrel{\circ}\over{.} 2
corresponds to an astrometric precision of ∼ 2 μ {as}. We generalize
expressions for image centroid displacements and variances in the
marginally resolved limit of interferometry to spectrally resolved data,
and use them to derive model-independent properties of the emission
such as its asymmetry, extension, and strong wavelength dependence. We
propose geometric models based on an extended and distorted wind and/or
a high-density gas stream, which has long been predicted to be present
in this system. The observations show that optical interferometry is
now able to resolve HMXBs at the spatial scale where accretion takes
place, and therefore to probe the effects of the gravitational and
radiation fields of the compact object on its environment.
---------------------------------------------------------
Title: Observing the Sun with the Atacama Large
Millimeter/submillimeter Array (ALMA): Fast-Scan Single-Dish Mapping
Authors: White, S. M.; Iwai, K.; Phillips, N. M.; Hills, R. E.; Hirota,
A.; Yagoubov, P.; Siringo, G.; Shimojo, M.; Bastian, T. S.; Hales,
A. S.; Sawada, T.; Asayama, S.; Sugimoto, M.; Marson, R. G.; Kawasaki,
W.; Muller, E.; Nakazato, T.; Sugimoto, K.; Brajša, R.; Skokić, I.;
Bárta, M.; Kim, S.; Remijan, A. J.; de Gregorio, I.; Corder, S. A.;
Hudson, H. S.; Loukitcheva, M.; Chen, B.; De Pontieu, B.; Fleishmann,
G. D.; Gary, D. E.; Kobelski, A.; Wedemeyer, S.; Yan, Y.
2017SoPh..292...88W Altcode: 2017arXiv170504766W
The Atacama Large Millimeter/submillimeter Array (ALMA) radio
telescope has commenced science observations of the Sun starting
in late 2016. Since the Sun is much larger than the field of view
of individual ALMA dishes, the ALMA interferometer is unable to
measure the background level of solar emission when observing the
solar disk. The absolute temperature scale is a critical measurement
for much of ALMA solar science, including the understanding of energy
transfer through the solar atmosphere, the properties of prominences,
and the study of shock heating in the chromosphere. In order to provide
an absolute temperature scale, ALMA solar observing will take advantage
of the remarkable fast-scanning capabilities of the ALMA 12 m dishes
to make single-dish maps of the full Sun. This article reports on the
results of an extensive commissioning effort to optimize the mapping
procedure, and it describes the nature of the resulting data. Amplitude
calibration is discussed in detail: a path that uses the two loads in
the ALMA calibration system as well as sky measurements is described
and applied to commissioning data. Inspection of a large number of
single-dish datasets shows significant variation in the resulting
temperatures, and based on the temperature distributions, we derive
quiet-Sun values at disk center of 7300 K at λ =3 mm and 5900 K at
λ =1.3 mm. These values have statistical uncertainties of about 100
K, but systematic uncertainties in the temperature scale that may be
significantly larger. Example images are presented from two periods
with very different levels of solar activity. At a resolution of about
25<SUP>″</SUP>, the 1.3 mm wavelength images show temperatures on
the disk that vary over about a 2000 K range. Active regions and plages
are among the hotter features, while a large sunspot umbra shows up as
a depression, and filament channels are relatively cool. Prominences
above the solar limb are a common feature of the single-dish images.
---------------------------------------------------------
Title: Gravitational wave signals from 3D neutrino hydrodynamics
simulations of core-collapse supernovae
Authors: Andresen, H.; Müller, B.; Müller, E.; Janka, H. -Th.
2017MNRAS.468.2032A Altcode: 2016arXiv160705199A
We present gravitational wave (GW) signal predictions from four
3D multigroup neutrino hydrodynamics simulations of core-collapse
supernovae of progenitors with 11.2, 20 and 27 M<SUB>⊙</SUB>. GW
emission in the pre-explosion phase strongly depends on whether the
post-shock flow is dominated by the standing accretion shock instability
(SASI) or convection and differs considerably from 2D models. SASI
activity produces a strong signal component below 250 Hz through
asymmetric mass motions in the gain layer and a non-resonant coupling to
the proto-neutron star (PNS). Both convection- and SASI-dominated models
show GW emission above 250 Hz, but with considerably lower amplitudes
than in 2D. This is due to a different excitation mechanism for
high-frequency l = 2 motions in the PNS surface, which are predominantly
excited by PNS convection in 3D. Resonant excitation of high-frequency
surface g modes in 3D by mass motions in the gain layer is suppressed
compared to 2D because of smaller downflow velocities and a lack
of high-frequency variability in the downflows. In the exploding 20
M<SUB>⊙</SUB> model, shock revival results in enhanced low-frequency
emission due to a change of the preferred scale of the convective eddies
in the PNS convection zone. Estimates of the expected excess power
in two frequency bands suggest that second-generation detectors will
only be able to detect very nearby events, but that third-generation
detectors could distinguish SASI- and convection-dominated models at
distances of ∼ 10 kpc.
---------------------------------------------------------
Title: First light for GRAVITY: Phase referencing optical
interferometry for the Very Large Telescope Interferometer
Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Amorim,
A.; Anugu, N.; Ávila, G.; Azouaoui, N.; Benisty, M.; Berger, J. P.;
Blind, N.; Bonnet, H.; Bourget, P.; Brandner, W.; Brast, R.; Buron,
A.; Burtscher, L.; Cassaing, F.; Chapron, F.; Choquet, É.; Clénet,
Y.; Collin, C.; Coudé Du Foresto, V.; de Wit, W.; de Zeeuw, P. T.;
Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; Dexter,
J.; Duvert, G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn,
M.; Fédou, P.; Finger, G.; Garcia, P.; Garcia Dabo, C. E.; Garcia
Lopez, R.; Gendron, E.; Genzel, R.; Gillessen, S.; Gonte, F.; Gordo,
P.; Grould, M.; Grözinger, U.; Guieu, S.; Haguenauer, P.; Hans,
O.; Haubois, X.; Haug, M.; Haussmann, F.; Henning, Th.; Hippler,
S.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.; Hummel, C. A.;
Jakob, G.; Janssen, A.; Jochum, L.; Jocou, L.; Kaufer, A.; Kellner,
S.; Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Klein, R.;
Kok, Y.; Kolb, J.; Kulas, M.; Lacour, S.; Lapeyrère, V.; Lazareff,
B.; Le Bouquin, J. -B.; Lèna, P.; Lenzen, R.; Lévêque, S.; Lippa,
M.; Magnard, Y.; Mehrgan, L.; Mellein, M.; Mérand, A.; Moreno-Ventas,
J.; Moulin, T.; Müller, E.; Müller, F.; Neumann, U.; Oberti, S.; Ott,
T.; Pallanca, L.; Panduro, J.; Pasquini, L.; Paumard, T.; Percheron,
I.; Perraut, K.; Perrin, G.; Pflüger, A.; Pfuhl, O.; Phan Duc, T.;
Plewa, P. M.; Popovic, D.; Rabien, S.; Ramírez, A.; Ramos, J.; Rau,
C.; Riquelme, M.; Rohloff, R. -R.; Rousset, G.; Sanchez-Bermudez,
J.; Scheithauer, S.; Schöller, M.; Schuhler, N.; Spyromilio, J.;
Straubmeier, C.; Sturm, E.; Suarez, M.; Tristram, K. R. W.; Ventura,
N.; Vincent, F.; Waisberg, I.; Wank, I.; Weber, J.; Wieprecht, E.;
Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez, J.; Wolff, B.;
Yazici, S.; Ziegler, D.; Zins, G.
2017A&A...602A..94G Altcode: 2017arXiv170502345G
GRAVITY is a new instrument to coherently combine the light of the
European Southern Observatory Very Large Telescope Interferometer to
form a telescope with an equivalent 130 m diameter angular resolution
and a collecting area of 200 m<SUP>2</SUP>. The instrument comprises
fiber fed integrated optics beam combination, high resolution
spectroscopy, built-in beam analysis and control, near-infrared
wavefront sensing, phase-tracking, dual-beam operation, and laser
metrology. GRAVITY opens up to optical/infrared interferometry the
techniques of phase referenced imaging and narrow angle astrometry,
in many aspects following the concepts of radio interferometry. This
article gives an overview of GRAVITY and reports on the performance and
the first astronomical observations during commissioning in 2015/16. We
demonstrate phase-tracking on stars as faint as m<SUB>K</SUB> ≈
10 mag, phase-referenced interferometry of objects fainter than
m<SUB>K</SUB> ≈ 15 mag with a limiting magnitude of m<SUB>K</SUB>
≈ 17 mag, minute long coherent integrations, a visibility accuracy
of better than 0.25%, and spectro-differential phase and closure
phase accuracy better than 0.5°, corresponding to a differential
astrometric precision of better than ten microarcseconds (μas). The
dual-beam astrometry, measuring the phase difference of two objects
with laser metrology, is still under commissioning. First observations
show residuals as low as 50 μas when following objects over several
months. We illustrate the instrument performance with the observations
of archetypical objects for the different instrument modes. Examples
include the Galactic center supermassive black hole and its fast
orbiting star S2 for phase referenced dual-beam observations and
infrared wavefront sensing, the high mass X-ray binary BP Cru and the
active galactic nucleus of PDS 456 for a few μas spectro-differential
astrometry, the T Tauri star S CrA for a spectro-differential visibility
analysis, ξ Tel and 24 Cap for high accuracy visibility observations,
and η Car for interferometric imaging with GRAVITY.
---------------------------------------------------------
Title: Accretion-ejection morphology of the microquasar SS 433
resolved at sub-au scale
Authors: GRAVITY Collaboration; Petrucci, P. -O.; Waisberg, I.; Le
Bouquin, J. -B.; Dexter, J.; Dubus, G.; Perraut, K.; Kervella, P.;
Abuter, R.; Amorim, A.; Anugu, N.; Berger, J. P.; Blind, N.; Bonnet,
H.; Brandner, W.; Buron, A.; Choquet, É.; Clénet, Y.; de Wit, W.;
Deen, C.; Eckart, A.; Eisenhauer, F.; Finger, G.; Garcia, P.; Garcia
Lopez, R.; Gendron, E.; Genzel, R.; Gillessen, S.; Gonte, F.; Haubois,
X.; Haug, M.; Haussmann, F.; Henning, Th.; Hippler, S.; Horrobin,
M.; Hubert, Z.; Jochum, L.; Jocou, L.; Kok, Y.; Kolb, J.; Kulas, M.;
Lacour, S.; Lazareff, B.; Lèna, P.; Lippa, M.; Mérand, A.; Müller,
E.; Ott, T.; Panduro, J.; Paumard, T.; Perrin, G.; Pfuhl, O.; Ramos,
J.; Rau, C.; Rohloff, R. -R.; Rousset, G.; Sanchez-Bermudez, J.;
Scheithauer, S.; Schöller, M.; Straubmeier, C.; Sturm, E.; Vincent,
F.; Wank, I.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski,
M.; Woillez, J.; Yazici, S.; Zins, G.
2017A&A...602L..11G Altcode: 2017arXiv170502359G
We present the first optical observation of the microquasar SS
433 at sub-milliarcsecond (mas) scale obtained with the GRAVITY
instrument on the Very Large Telescope interferometer (VLTI). The
3.5-h exposure reveals a rich K-band spectrum dominated by hydrogen
Brγand He I lines, as well as (red-shifted)emission lines coming
from the jets. The K-band-continuum-emitting region is dominated
by a marginally resolved point source (<1 mas) embedded inside a
diffuse background accounting for 10% of the total flux. The jet line
positions agree well with the ones expected from the jet kinematic
model, an interpretation also supported by the consistent sign (i.e.,
negative/positive for the receding/approaching jet component) of the
phase shifts observed in the lines. The significant visibility drop
across the jet lines, together with the small and nearly identical
phases for all baselines, point toward a jet that is offset by less
than 0.5 mas from the continuum source and resolved in the direction
of propagation, with a typical size of 2 mas. The jet position angle of
~80° is consistent with the expected one at the observation date. Jet
emission so close to the central binary system would suggest that line
locking, if relevant to explain the amplitude and stability of the
0.26c jet velocity, operates on elements heavier than hydrogen. The
Brγprofile is broad and double peaked. It is better resolved than the
continuum and the change of the phase signal sign across the line on
all baselines suggests an East-West-oriented geometry similar to the
jet direction and supporting a (polar) disk wind origin. <P />Based
on observations made with VLTI/Gravity instrument.
---------------------------------------------------------
Title: VizieR Online Data Catalog: YSO candidates in the Magellanic
Bridge (Chen+, 2014)
Authors: Chen, C. -H. R.; Indebetouw, R.; Muller, E.; Kawamura, A.;
Gordon, K. D.; Sewilo, M.; Whitney, B. A.; Fukui, Y.; Madden, S. C.;
Meade, M. R.; Meixner, M.; Oliveira, J. M.; Robitaille, T. P.; Seale,
J. P.; Shiao, B.; van Loon, J. Th.
2017yCat..17850162C Altcode:
The Spitzer observations of the Bridge were obtained as part of
the Legacy Program "Surveying the Agents of Galaxy Evolution in the
Tidally-Stripped, Low-Metallicity Small Magellanic Cloud" (SAGE-SMC;
Gordon et al. 2011AJ....142..102G). These observations included images
taken at 3.6, 4.5, 5.8, and 8.0 um bands with the InfraRed Array Camera
(IRAC) and at 24, 70, and 160 um bands with the Multiband Imaging
Photometer for Spitzer (MIPS). The details of data processing are given
in Gordon et al. (2011AJ....142..102G). To construct multi-wavelength
SEDs for sources in the Spitzer catalog, we have expanded it by
adding photometry from optical and NIR surveys covering the Bridge,
i.e., BRI photometry from the Super COSMOS Sky Surveys (SSS; Hambly et
al. 2001MNRAS.326.1279H) and JHKs photometry from the Two Micron All Sky
Survey (2MASS; Skrutskie et al. 2006AJ....131.1163S, Cat. VII/233). <P
/>(5 data files).
---------------------------------------------------------
Title: SEDIGISM: Structure, excitation, and dynamics of the inner
Galactic interstellar medium
Authors: Schuller, F.; Csengeri, T.; Urquhart, J. S.; Duarte-Cabral,
A.; Barnes, P. J.; Giannetti, A.; Hernandez, A. K.; Leurini, S.;
Mattern, M.; Medina, S. -N. X.; Agurto, C.; Azagra, F.; Anderson,
L. D.; Beltrán, M. T.; Beuther, H.; Bontemps, S.; Bronfman, L.; Dobbs,
C. L.; Dumke, M.; Finger, R.; Ginsburg, A.; Gonzalez, E.; Henning,
T.; Kauffmann, J.; Mac-Auliffe, F.; Menten, K. M.; Montenegro-Montes,
F. M.; Moore, T. J. T.; Muller, E.; Parra, R.; Perez-Beaupuits,
J. -P.; Pettitt, A.; Russeil, D.; Sánchez-Monge, Á.; Schilke, P.;
Schisano, E.; Suri, S.; Testi, L.; Torstensson, K.; Venegas, P.;
Wang, K.; Wienen, M.; Wyrowski, F.; Zavagno, A.
2017A&A...601A.124S Altcode: 2017arXiv170104712S
Context. The origin and life-cycle of molecular clouds are still
poorly constrained, despite their importance for understanding the
evolution of the interstellar medium. Many large-scale surveys of
the Galactic plane have been conducted recently, allowing for rapid
progress in this field. Nevertheless, a sub-arcminute resolution
global view of the large-scale distribution of molecular gas,
from the diffuse medium to dense clouds and clumps, and of their
relationshipto the spiral structure, is still missing. <BR /> Aims:
We have carried out a systematic, homogeneous, spectroscopic survey of
the inner Galactic plane, in order to complement the many continuum
Galactic surveys available with crucial distance and gas-kinematic
information. Our aim is to combine this data set with recent infrared
to sub-millimetre surveys at similar angular resolutions. <BR />
Methods: The SEDIGISM survey covers 78 deg<SUP>2</SUP> of the inner
Galaxy (-60°≤ℓ≤ 18°, |b|≤ 0.5°) in the J = 2-1 rotational
transition of <SUP>13</SUP>CO. This isotopologue of CO is less abundant
than <SUP>12</SUP>CO by factors up to 100. Therefore, its emission
has low to moderate optical depths, and higher critical density,
making it an ideal tracer of the cold, dense interstellar medium. The
data have been observed with the SHFI single-pixel instrument
at APEX. The observational setup covers the <SUP>13</SUP>CO(2-1)
and C<SUP>18</SUP>O(2-1) lines, plus several transitions from other
molecules. <BR /> Results: The observations have been completed. Data
reduction is in progress, and the final data products will be made
available in the near future. Here we give a detailed description of
the survey and the dedicated data reduction pipeline. To illustrate
the scientific potential of this survey, preliminary results based on
a science demonstration field covering -20°≤ℓ ≤ -18.5° are
presented. Analysis of the <SUP>13</SUP>CO(2-1) data in this field
reveals compact clumps, diffuse clouds, and filamentary structures
at a range of heliocentric distances. By combining our data with
data in the (1-0) transition of CO isotopologues from the ThrUMMS
survey, we are able to compute a 3D realization of the excitation
temperature and optical depth in the interstellar medium. Ultimately,
this survey will provide a detailed, global view of the inner Galactic
interstellar medium at an unprecedented angular resolution of 30”. <P
/>This publication is based on data acquired with the Atacama Pathfinder
EXperiment (APEX) under programmes 092.F-9315(A) and 193.C-0584(A). APEX
is a collaboration between the Max-Planck-Institut für Radioastronomie,
the European Southern Observatory, and the Onsala Space Observatory.Full
Table 5 and Table A.1 are only available at the CDS via anonymous ftp
to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(<A href="http://130.79.128.5">http://130.79.128.5</A>) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/601/A124">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/601/A124</A>
---------------------------------------------------------
Title: VizieR Online Data Catalog: Clouds in SEDIGISM science
demonstration field (Schuller+, 2017)
Authors: Schuller, F.; Csengeri, T.; Urquhart, J. S.; Duarte-Cabral,
A.; Barnes, P. J.; Giannetti, A.; Hernandez, A. K.; Leurini, S.;
Mattern, M.; Medina, S. -N. X.; Agurto, C.; Azagra, F.; Anderson,
L. D.; Beltran, M. T.; Beuther, H.; Bontemps, S.; Bronfman, L.; Dobbs,
C. L.; Dumke, M.; Finger, R.; Ginsburg, A.; Gonzalez, E.; Henning,
T.; Kauffmann, J.; Mac-Auliffe, F.; Menten, K. M.; Montenegro-Montes,
F. M.; Moore, T. J. T.; Muller, E.; Parra, R.; Perez-Beaupuits,
J. -P.; Pettitt, A.; Russeil, D.; Sanchez-Monge, A.; Schilke, P.;
Schisano, E.; Suri, S.; Testi, L.; Torstensson, K.; Venegas, P.;
Wang, K.; Wienen, M.; Wyrowski, F.; Zavagno, A.
2017yCat..36010124S Altcode:
Properties of ATLASGAL compact sources located in the SEDIGISM
science demonstration field, and properties of molecular clouds and
complexes extracted from the <SUP>13</SUP>CO(2-1) data covering the
same field. The extraction of clouds was performed using the SCIMES
algorithm (Colombo et al., 2015MNRAS.454.2067C). <P />(2 data files).
---------------------------------------------------------
Title: The ALMA Science Archive
Authors: Stoehr, F.; Manning, A.; Moins, C.; Jenkins, D.; Lacy, M.;
Leon, S.; Muller, E.; Nakanishi, K.; Matthews, B.; Gaudet, S.; Murphy,
E.; Ashitagawa, K.; Kawamura, A.
2017Msngr.167....2S Altcode:
Science archives help to maximise the scientific return of astronomical
facilities. After placing science archives into a slightly larger
context, we describe the current status and capabilities of the ALMA
Science Archive. We present the design principles and technology
employed for three main contexts: query; result set display; and data
download. A summary of the ALMA data flow is also presented as are
access statistics to date.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Galactic
CHaMP. III. <SUP>12</SUP>CO dense clump properties (Barnes+,
Authors: Barnes, P. J.; Hernandez, A. K.; O'Dougherty, S. N.; Schap,
W. J., III; Muller, E.
2017yCat..18310067B Altcode:
In Phase II of the Mopra observing for the Census of High- and
Medium-mass Protostars (CHaMP) project during 2009-12, we tuned the
receiver to a central frequency of 111.3GHz and set up the Mopra
Spectrometer (MOPS) digital filterbank to map all the CHaMP clumps in
a second set of spectral lines at frequencies of 107-115GHz. This new
set of transitions most notably includes the J=1->0 lines for the
triad of CO-isotopologue species, <SUP>12</SUP>CO, <SUP>13</SUP>CO,
and C<SUP>18</SUP>O. <P />(3 data files).
---------------------------------------------------------
Title: Supernovae from the 8-10 M_⊙ range: the first spectral
models for the emission-line phase
Authors: Jerkstrand, A.; Ertl, T.; Janka, H. -T.; Müller, E.
2017MmSAI..88..278J Altcode:
Stars in the M<SUB>ZAMS</SUB>=8-10 M_⊙ range are expected to
account for about 1/3 of all core-collapse supernovae (SNe). Here we
describe calculations of the first spectral models in the nebular
phase (t>200d) for such SNe, and the diagnostic potential of
these. Comparison of a 9 M_⊙ SN model with SN 1997D suggests that
the observational class of subluminous Type IIP SNe is linked to
the low-mass end of progenitors. We discuss potential diagnostics of
electron capture supernovae from <SUP>58</SUP>Ni lines.
---------------------------------------------------------
Title: Magnetorotational Instability in Core-collapse Supernovae
Authors: Rembiasz, T.; Obergaulinger, M.; Guilet, J.; Cerdá-Durán,
P.; Aloy, M. A.; Müller, E.
2017AcPPS..10..361R Altcode: 2017arXiv170700983R
We discuss the relevance of the magnetorotational instability (MRI)
in core-collapse supernovae (CCSNe). Our recent numerical studies show
that in CCSNe, the MRI is terminated by parasitic instabilities of
the Kelvin-Helmholtz type. To determine whether the MRI can amplify
initially weak magnetic fields to dynamically relevant strengths in
CCSNe, we performed three-dimensional simulations of a region close to
the surface of a differentially rotating proto-neutron star in non-ideal
magnetohydrodynamics with two different numerical codes. We find
that under the conditions prevailing in proto-neutron stars, the MRI
can amplify the magnetic field by (only) one order of magnitude. This
severely limits the role of MRI channel modes as an agent amplifying the
magnetic field in proto-neutron stars starting from small seed fields.
---------------------------------------------------------
Title: Radiative and mechanical feedback into the molecular gas in
the Large Magellanic Cloud. I. N159W
Authors: Lee, M. -Y.; Madden, S. C.; Lebouteiller, V.; Gusdorf, A.;
Godard, B.; Wu, R.; Galametz, M.; Cormier, D.; Le Petit, F.; Roueff,
E.; Bron, E.; Carlson, L.; Chevance, M.; Fukui, Y.; Galliano, F.;
Hony, S.; Hughes, A.; Indebetouw, R.; Israel, F. P.; Kawamura, A.;
Le Bourlot, J.; Lesaffre, P.; Meixner, M.; Muller, E.; Nayak, O.;
Onishi, T.; Roman-Duval, J.; Sewiło, M.
2016A&A...596A..85L Altcode: 2016arXiv160604290L
We present Herschel SPIRE Fourier Transform Spectrometer (FTS)
observations of N159W, an active star-forming region in the Large
Magellanic Cloud (LMC). In our observations, a number of far-infrared
cooling lines, including carbon monoxide (CO) J = 4 → 3 to J =
12 → 11, [CI] 609 μm and 370 μm, and [NII] 205 μm, are clearly
detected. With an aim of investigating the physical conditions
and excitation processes of molecular gas, we first construct
CO spectral line energy distributions (SLEDs) on 10 pc scales by
combining the FTS CO transitions with ground-based low-J CO data
and analyze the observed CO SLEDs using non-LTE (local thermodynamic
equilibrium) radiative transfer models. We find that the CO-traced
molecular gas in N159W is warm (kinetic temperature of 153-754 K)
and moderately dense (H<SUB>2</SUB> number density of (1.1-4.5)
× 10<SUP>3</SUP> cm<SUP>-3</SUP>). To assess the impact of the
energetic processes in the interstellar medium on the physical
conditions of the CO-emitting gas, we then compare the observed
CO line intensities with the models of photodissociation regions
(PDRs) and shocks. We first constrain the properties of PDRs by
modeling Herschel observations of [OI] 145 μm, [CII] 158 μm, and
[CI] 370 μm fine-structure lines and find that the constrained PDR
components emit very weak CO emission. X-rays and cosmic-rays are
also found to provide a negligible contribution to theCO emission,
essentially ruling out ionizing sources (ultraviolet photons, X-rays,
and cosmic-rays) as the dominant heating source for CO in N159W. On the
other hand, mechanical heating by low-velocity C-type shocks with 10 km
s<SUP>-1</SUP> appears sufficient enough to reproduce the observed warm
CO. <P />Herschel is an ESA space observatory with science instruments
provided by European-led Principal Investigator consortia and with
important participation from NASA.The final reduced Herschel data
(FITS files) are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(<A href="http://130.79.128.5">http://130.79.128.5</A>) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/596/A85">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/596/A85</A>
---------------------------------------------------------
Title: APSARA: A multi-dimensional unsplit fourth-order explicit
Eulerian hydrodynamics code for arbitrary curvilinear grids
Authors: Wongwathanarat, A.; Grimm-Strele, H.; Müller, E.
2016A&A...595A..41W Altcode: 2016arXiv160704272W
We present a new fourth-order, finite-volume hydrodynamics code named
Apsara. The code employs a high-order, finite-volume method for mapped
coordinates with extensions for nonlinear hyperbolic conservation
laws. Apsara can handle arbitrary structured curvilinear meshes in
three spatial dimensions. The code has successfully passed several
hydrodynamic test problems, including the advection of a Gaussian
density profile and a nonlinear vortex and the propagation of linear
acoustic waves. For these test problems, Apsara produces fourth-order
accurate results in case of smooth grid mappings. The order of accuracy
is reduced to first-order when using the nonsmooth circular grid
mapping. When applying the high-order method to simulations of low-Mach
number flows, for example, the Gresho vortex and the Taylor-Green
vortex, we discover that Apsara delivers superior results to codes based
on the dimensionally split, piecewise parabolic method (PPM) widely
used in astrophysics. Hence, Apsara is a suitable tool for simulating
highly subsonic flows in astrophysics. In the first astrophysical
application, we perform implicit large eddy simulations (ILES)
of anisotropic turbulence in the context of core collapse supernova
(CCSN) and obtain results similar to those previously reported.
---------------------------------------------------------
Title: From ATLASGAL to SEDIGISM: Towards a Complete 3D View of the
Dense Galactic Interstellar Medium
Authors: Schuller, F.; Urquhart, J.; Bronfman, L.; Csengeri, T.;
Bontemps, S.; Duarte-Cabral, A.; Giannetti, A.; Ginsburg, A.; Henning,
T.; Immer, K.; Leurini, S.; Mattern, M.; Menten, K.; Molinari, S.;
Muller, E.; Sánchez-Monge, A.; Schisano, E.; Suri, S.; Testi, L.;
Wang, K.; Wyrowski, F.; Zavagno, A.
2016Msngr.165...27S Altcode: 2016Msngr.165...27U
The ATLASGAL survey has provided the first unbiased view of the inner
Galactic Plane at sub-millimetre wavelengths. This is the largest
ground-based survey of its kind to date, covering 420 square degrees
at a wavelength of 870 µm. The reduced data, consisting of images and
a catalogue of > 10<SUP>4</SUP> compact sources, are available from
the ESO Science Archive Facility through the Phase 3 infrastructure. The
extremely rich statistics of this survey initiated several follow-up
projects, including spectroscopic observations to explore molecular
complexity and high angular resolution imaging with the Atacama Large
Millimeter/submillimeter Array (ALMA), aimed at resolving individual
protostars. The most extensive follow-up project is SEDIGISM, a 3D
mapping of the dense interstellar medium over a large fraction of the
inner Galaxy. Some notable results of these surveys are highlighted.
---------------------------------------------------------
Title: On the maximum magnetic field amplification by the
magnetorotational instability in core-collapse supernovae
Authors: Rembiasz, T.; Guilet, J.; Obergaulinger, M.; Cerdá-Durán,
P.; Aloy, M. A.; Müller, E.
2016MNRAS.460.3316R Altcode: 2016arXiv160300466R; 2016MNRAS.tmp..888R
Whether the magnetorotational instability (MRI) can amplify initially
weak magnetic fields to dynamically relevant strengths in core-collapse
supernovae is still a matter of active scientific debate. Recent
numerical studies have shown that the first phase of MRI growth
dominated by channel flows is terminated by parasitic instabilities of
the Kelvin-Helmholtz type that disrupt MRI channel flows and quench
further magnetic field growth. However, it remains to be properly
assessed by what factor the initial magnetic field can be amplified
and how it depends on the initial field strength and the amplitude of
the perturbations. Different termination criteria leading to different
estimates of the amplification factor were proposed within the parasitic
model. To determine the amplification factor and test which criterion is
a better predictor of the MRI termination, we perform three-dimensional
shearing-disc and shearing-box simulations of a region close to the
surface of a differentially rotating protoneutron star in non-ideal
magnetohydrodynamics with two different numerical codes. We find that
independently of the initial magnetic field strength, the MRI channel
modes can amplify the magnetic field by, at most, a factor of 100. Under
the conditions found in protoneutron stars, a more realistic value for
the magnetic field amplification is of the order of 10. This severely
limits the role of the MRI channel modes as an agent amplifying the
magnetic field in protoneutron stars starting from small seed fields. A
further amplification should therefore rely on other physical processes,
such as for example an MRI-driven turbulent dynamo.
---------------------------------------------------------
Title: Shear mixing in stellar radiative zones. II. Robustness of
numerical simulations
Authors: Prat, V.; Guilet, J.; Viallet, M.; Müller, E.
2016A&A...592A..59P Altcode: 2015arXiv151204223P
Context. Recent numerical simulations suggest that the model by Zahn
(1992, A&A, 265, 115) for the turbulent mixing of chemical elements
due to differential rotation in stellar radiative zones is valid. <BR
/> Aims: We investigate the robustness of this result with respect
to the numerical configuration and Reynolds number of the flow. <BR
/> Methods: We compare results from simulations performed with two
different numerical codes, including one that uses the shearing-box
formalism. We also extensively study the dependence of the turbulent
diffusion coefficient on the turbulent Reynolds number. <BR /> Results:
The two numerical codes used in this study give consistent results. The
turbulent diffusion coefficient is independent of the size of the
numerical domain if at least three large turbulent structures fit in
the box. Generally, the turbulent diffusion coefficient depends on
the turbulent Reynolds number. However, our simulations suggest that
an asymptotic regime is obtained when the turbulent Reynolds number
is larger than 10<SUP>3</SUP>. <BR /> Conclusions: Shear mixing in
the regime of small Péclet numbers can be investigated numerically
both with shearing-box simulations and simulations using explicit
forcing. Our results suggest that Zahn's model is valid at large
turbulent Reynolds numbers.
---------------------------------------------------------
Title: System tests and on-sky commissioning of the GRAVITY-CIAO
wavefront sensors
Authors: Deen, C.; Kolb, J.; Oberti, S.; Bonnet, H.; Müller, E.;
Hubert, Z.; Zins, G.; Delplancke, F.; Haguenauer, P.; Pettazzi, L.;
Bourget, P.; Suarez-Valles, M.; Scheithauer, S.; Huber, A.; Esselborn,
M.; Clenét, Y.; Gendron, E.; Brandner, W.; Klein, R.; Lenzen, R.;
Neumann, Udo; Kulas, M.; Panduro, J.; Ramos, J.; Rohloff, R. -R.;
Henning, T.; Perraut, K.; Perrin, G.; Straubmeier, C.; Amorim, A.;
Eisenhauer, F.
2016SPIE.9909E..2MD Altcode:
GRAVITY is a near-infrared interferometric instrument that allows
astronomers to combine the light of the four unit or four auxiliary
telescopes of the ESO Very Large Telescope in Paranal, Chile. GRAVITY
will deliver extremely precise relative astrometry and spatially
resolved spectra. In order to study objects in regions of high
extinction (e.g. the Galactic Center, or star forming regions), GRAVITY
will use infrared wavefront sensors. The suite of four wavefront
sensors located in the Coudé room of each of the unit telescopes
are known as the Coudé Integrated Adaptive Optics (CIAO). The CIAO
wavefront sensors are being constructed by the Max Planck Institute for
Astronomy (MPIA) and are being installed and commissioned at Paranal
between February and September of 2016. This presentation will focus
on system tests performed in the MPIA adaptive optics laboratory in
Heidelberg, Germany in preparation for shipment to Paranal, as well
as on-sky data from the commissioning of the first instrument. We
will discuss the CIAO instruments, control strategy, optimizations,
and performance at the telescope.
---------------------------------------------------------
Title: Termination of the MRI via parasitic instabilities in
core-collapse supernovae: influence of numerical methods
Authors: Rembiasz, T.; Obergaulinger, M.; Cerdá-Durán, P.; Aloy,
M. Á.; Müller, E.
2016JPhCS.719a2009R Altcode: 2016arXiv160505200R
We study the influence of numerical methods and grid resolution
on the termination of the magnetorotational instability (MRI) by
means of parasitic instabilities in threedimensional shearing-disc
simulations reproducing typical conditions found in core-collapse
supernovae. Whether or not the MRI is able to amplify weak magnetic
fields in this context strongly depends, among other factors, on the
amplitude at which its growth terminates. The qualitative results of
our study do not depend on the numerical scheme. In all our models, MRI
termination is caused by Kelvin-Helmholtz instabilities, consistent with
theoretical predictions. Quantitatively, however, there are differences,
but numerical convergence can be achieved even at relatively low grid
resolutions if high-order reconstruction methods are used.
---------------------------------------------------------
Title: Termination of the magnetorotational instability via parasitic
instabilities in core-collapse supernovae
Authors: Rembiasz, T.; Obergaulinger, M.; Cerdá-Durán, P.; Müller,
E.; Aloy, M. A.
2016MNRAS.456.3782R Altcode: 2015arXiv150804799R
The magnetorotational instability (MRI) can be a powerful mechanism
amplifying the magnetic field in core-collapse supernovae. Whether
initially weak magnetic fields can be amplified by this instability
to dynamically relevant strengths is still a matter of debate. One of
the main uncertainties concerns the process that terminates the growth
of the instability. Parasitic instabilities of both Kelvin-Helmholtz
and tearing-mode type have been suggested to play a crucial role in
this process, disrupting MRI channel flows and quenching magnetic
field amplification. We perform two-dimensional and three-dimensional
sheering-disc simulations of a differentially rotating protoneutron
star layer in non-ideal magnetohydrodynamics with unprecedented high
numerical accuracy, finding that Kelvin-Helmholtz parasitic modes
dominate tearing modes in the regime of large hydrodynamic and magnetic
Reynolds numbers, as encountered close to the surface of protoneutron
stars. They also determine the maximum magnetic field stress achievable
during the exponential growth of the MRI. Our results are consistent
with the theory of parasitic instabilities based on a local stability
analysis. To simulate the Kelvin-Helmholtz instabilities properly, a
very high numerical resolution is necessary. Using ninth-order spatial
reconstruction schemes, we find that at least eight grid zones per
MRI channel are necessary to simulate the growth phase of the MRI
and reach an accuracy of ∼10 per cent in the growth rate, while
more than ∼60 zones per channel are required to achieve convergent
results for the value of the magnetic stress at MRI termination.
---------------------------------------------------------
Title: Candidate Filament Collision in the SMC; Energy Distribution
within the SFR N66/NGC346
Authors: Muller, E.; Kempen, T.; Mizuno, N.; Kawamura, A.; Minamidani,
T.
2015ASPC..499..251M Altcode:
The N66 nebula in the SMC is associated with NGC346, the brightest,
most magnificent and iconic star-forming region in the metal-poor and
CO-underluminous Small Magellanic Cloud. More than half the entire SMC
O-star population and 6% of the current-era starformation is located in
this small ∼ 80 pc region. The little research undertaken towards N66
focuses on only measurements of the CO and continuum surface-brightness,
without a detailed kinematic and energetic emphasis. We explore these
aspects here, and discuss a candidate formation scenario for this
astonishing, and entirely enigmatic structure in the SMC.
---------------------------------------------------------
Title: Dense Molecular Clumps Associated with the LMC Supergiant
Shell LMC 4 & LMC 5
Authors: Fujii, K.; Minamidani, T.; Mizuno, N.; Onishi, T.; Kawamura,
A.; Muller, E.; Dawson, J.; Fukui, Y.
2015ASPC..499..255F Altcode:
The <SUP>12</SUP>CO(J=3-2/1-0) and <SUP>13</SUP>CO(J=3-2/1-0)
observations with ASTE and Mopra telescopes have been carried out
toward the giant molecular clouds (GMCs) in the N48/N49 regions in the
Large Magellanic Cloud (LMC), which are located at the boundary of two
kpc-scale Supergiant Shell (SGS) LMC 4 & LMC 5. The star formation
is relatively evolved in the N48 region, which is just located at the
boundary of SGSs, than in the N49 region. The clumps in the N48 show
higher n(H<SUB>2</SUB>) and T<SUB>kin</SUB> than those in the N49, but
their densities are not so high as the LMC cluster forming clumps. The
collision of two SGSs actually enhances the star formation but further
evolution seem to be necessary for subsequent cluster formation.
---------------------------------------------------------
Title: Supernova 1987A: neutrino-driven explosions in three dimensions
and light curves
Authors: Utrobin, V. P.; Wongwathanarat, A.; Janka, H. -Th.;
Müller, E.
2015A&A...581A..40U Altcode: 2014arXiv1412.4122U
Context. The well-observed and well-studied type IIP Supernova 1987A
(SN 1987A), produced by the explosion of a blue supergiant in the Large
Magellanic Cloud, is a touchstone for the evolution of massive stars,
the simulation of neutrino-driven explosions, and the modeling of light
curves and spectra. <BR /> Aims: In the framework of the neutrino-driven
explosion mechanism, we study the dependence of explosion properties
on the structure of different blue supergiant progenitors and compare
the corresponding light curves with observations of SN 1987A. <BR
/> Methods: Three-dimensional (3D) simulations of neutrino-driven
explosions are performed with the explicit, finite-volume, Eulerian,
multifluid hydrodynamics code Prometheus, using of four available
presupernova models as initial data. At a stage of almost homologous
expansion, the hydrodynamical and composition variables of the 3D models
are mapped to a spherically symmetric configuration, and the simulations
are continued with the implicit, Lagrangian radiation-hydrodynamics code
Crab to follow the blast-wave evolution into the SN outburst. <BR />
Results: All of our 3D neutrino-driven explosion models, with explosion
energies compatible with SN 1987A, produce <SUP>56</SUP>Ni in rough
agreement with the amount deduced from fitting the radioactively powered
light-curve tail. Two of our models (based on the same progenitor)
yield maximum velocities of around 3000 km s<SUP>-1</SUP> for the bulk
of ejected <SUP>56</SUP>Ni, consistent with observational data. In all
of our models inward mixing of hydrogen during the 3D evolution leads to
minimum velocities of hydrogen-rich matter below 100 km s<SUP>-1</SUP>,
which is in good agreement with spectral observations. However, the
explosion of only one of the considered progenitors reproduces the
shape of the broad light curve maximum of SN 1987A fairly well. <BR
/> Conclusions: The considered presupernova models, 3D explosion
simulations, and light-curve calculations can explain the basic
observational features of SN 1987A, except for those connected to the
presupernova structure of the outer stellar layers. All progenitors
have presupernova radii that are too large to reproduce the narrow
initial luminosity peak, and the structure of their outer layers is
not suitable to match the observed light curve during the first 30-40
days. Only one stellar model has a structure of the helium core and the
He/H composition interface that enables sufficient outward mixing of
<SUP>56</SUP>Ni and inward mixing of hydrogen to produce a good match
of the dome-like shape of the observed light-curve maximum, but this
model falls short of the helium-core mass of 6 M<SUB>⊙</SUB> inferred
from the absolute luminosity of the presupernova star. The lack of an
adequate presupernova model for the well-studied SN 1987A is a real
and pressing challenge for the theory of the evolution of massive stars.
---------------------------------------------------------
Title: The Future of Astronomy and the ALMA Archive
Authors: Stoehr, F.; Lacy, M.; Leon, S.; Muller, E.; Kawamura, A.
2015ASPC..495...69S Altcode: 2015adass..24...69S
Astronomy is changing as the amount and complexity of data taken
grows. We argue that in the future observatories will compete for
astronomers to work with their data, that observatories will have to
reorient themselves to from providing good data only to providing
an excellent end-to-end user-experience with all its implications,
that science-grade data-reduction pipelines will become an integral
part of the design of a new observatory or instrument and that all
this evolution will have a deep impact on how astronomers will do
science. We show how ALMA's general design principles are in line with
this paradigm and how the ALMA archive fits into this picture.
---------------------------------------------------------
Title: The 2014 ALMA Long Baseline Campaign: An Overview
Authors: ALMA Partnership; Fomalont, E. B.; Vlahakis, C.; Corder,
S.; Remijan, A.; Barkats, D.; Lucas, R.; Hunter, T. R.; Brogan,
C. L.; Asaki, Y.; Matsushita, S.; Dent, W. R. F.; Hills, R. E.;
Phillips, N.; Richards, A. M. S.; Cox, P.; Amestica, R.; Broguiere,
D.; Cotton, W.; Hales, A. S.; Hiriart, R.; Hirota, A.; Hodge, J. A.;
Impellizzeri, C. M. V.; Kern, J.; Kneissl, R.; Liuzzo, E.; Marcelino,
N.; Marson, R.; Mignano, A.; Nakanishi, K.; Nikolic, B.; Perez,
J. E.; Pérez, L. M.; Toledo, I.; Aladro, R.; Butler, B.; Cortes,
J.; Cortes, P.; Dhawan, V.; Di Francesco, J.; Espada, D.; Galarza,
F.; Garcia-Appadoo, D.; Guzman-Ramirez, L.; Humphreys, E. M.; Jung,
T.; Kameno, S.; Laing, R. A.; Leon, S.; Mangum, J.; Marconi, G.;
Nagai, H.; Nyman, L. -A.; Radiszcz, M.; Rodón, J. A.; Sawada, T.;
Takahashi, S.; Tilanus, R. P. J.; van Kempen, T.; Vila Vilaro, B.;
Watson, L. C.; Wiklind, T.; Gueth, F.; Tatematsu, K.; Wootten, A.;
Castro-Carrizo, A.; Chapillon, E.; Dumas, G.; de Gregorio-Monsalvo, I.;
Francke, H.; Gallardo, J.; Garcia, J.; Gonzalez, S.; Hibbard, J. E.;
Hill, T.; Kaminski, T.; Karim, A.; Krips, M.; Kurono, Y.; Lopez, C.;
Martin, S.; Maud, L.; Morales, F.; Pietu, V.; Plarre, K.; Schieven,
G.; Testi, L.; Videla, L.; Villard, E.; Whyborn, N.; Zwaan, M. A.;
Alves, F.; Andreani, P.; Avison, A.; Barta, M.; Bedosti, F.; Bendo,
G. J.; Bertoldi, F.; Bethermin, M.; Biggs, A.; Boissier, J.; Brand,
J.; Burkutean, S.; Casasola, V.; Conway, J.; Cortese, L.; Dabrowski,
B.; Davis, T. A.; Diaz Trigo, M.; Fontani, F.; Franco-Hernandez, R.;
Fuller, G.; Galvan Madrid, R.; Giannetti, A.; Ginsburg, A.; Graves,
S. F.; Hatziminaoglou, E.; Hogerheijde, M.; Jachym, P.; Jimenez Serra,
I.; Karlicky, M.; Klaasen, P.; Kraus, M.; Kunneriath, D.; Lagos, C.;
Longmore, S.; Leurini, S.; Maercker, M.; Magnelli, B.; Marti Vidal,
I.; Massardi, M.; Maury, A.; Muehle, S.; Muller, S.; Muxlow, T.;
O'Gorman, E.; Paladino, R.; Petry, D.; Pineda, J. E.; Randall, S.;
Richer, J. S.; Rossetti, A.; Rushton, A.; Rygl, K.; Sanchez Monge,
A.; Schaaf, R.; Schilke, P.; Stanke, T.; Schmalzl, M.; Stoehr, F.;
Urban, S.; van Kampen, E.; Vlemmings, W.; Wang, K.; Wild, W.; Yang,
Y.; Iguchi, S.; Hasegawa, T.; Saito, M.; Inatani, J.; Mizuno, N.;
Asayama, S.; Kosugi, G.; Morita, K. -I.; Chiba, K.; Kawashima, S.;
Okumura, S. K.; Ohashi, N.; Ogasawara, R.; Sakamoto, S.; Noguchi, T.;
Huang, Y. -D.; Liu, S. -Y.; Kemper, F.; Koch, P. M.; Chen, M. -T.;
Chikada, Y.; Hiramatsu, M.; Iono, D.; Shimojo, M.; Komugi, S.; Kim,
J.; Lyo, A. -R.; Muller, E.; Herrera, C.; Miura, R. E.; Ueda, J.;
Chibueze, J.; Su, Y. -N.; Trejo-Cruz, A.; Wang, K. -S.; Kiuchi,
H.; Ukita, N.; Sugimoto, M.; Kawabe, R.; Hayashi, M.; Miyama, S.;
Ho, P. T. P.; Kaifu, N.; Ishiguro, M.; Beasley, A. J.; Bhatnagar,
S.; Braatz, J. A., III; Brisbin, D. G.; Brunetti, N.; Carilli, C.;
Crossley, J. H.; D'Addario, L.; Donovan Meyer, J. L.; Emerson, D. T.;
Evans, A. S.; Fisher, P.; Golap, K.; Griffith, D. M.; Hale, A. E.;
Halstead, D.; Hardy, E. J.; Hatz, M. C.; Holdaway, M.; Indebetouw, R.;
Jewell, P. R.; Kepley, A. A.; Kim, D. -C.; Lacy, M. D.; Leroy, A. K.;
Liszt, H. S.; Lonsdale, C. J.; Matthews, B.; McKinnon, M.; Mason,
B. S.; Moellenbrock, G.; Moullet, A.; Myers, S. T.; Ott, J.; Peck,
A. B.; Pisano, J.; Radford, S. J. E.; Randolph, W. T.; Rao Venkata,
U.; Rawlings, M. G.; Rosen, R.; Schnee, S. L.; Scott, K. S.; Sharp,
N. K.; Sheth, K.; Simon, R. S.; Tsutsumi, T.; Wood, S. J.
2015ApJ...808L...1A Altcode: 2015arXiv150404877P
A major goal of the Atacama Large Millimeter/submillimeter Array (ALMA)
is to make accurate images with resolutions of tens of milliarcseconds,
which at submillimeter (submm) wavelengths requires baselines up to
∼15 km. To develop and test this capability, a Long Baseline Campaign
(LBC) was carried out from 2014 September to late November, culminating
in end-to-end observations, calibrations, and imaging of selected
Science Verification (SV) targets. This paper presents an overview
of the campaign and its main results, including an investigation of
the short-term coherence properties and systematic phase errors over
the long baselines at the ALMA site, a summary of the SV targets and
observations, and recommendations for science observing strategies at
long baselines. Deep ALMA images of the quasar 3C 138 at 97 and 241 GHz
are also compared to VLA 43 GHz results, demonstrating an agreement at
a level of a few percent. As a result of the extensive program of LBC
testing, the highly successful SV imaging at long baselines achieved
angular resolutions as fine as 19 mas at ∼350 GHz. Observing with
ALMA on baselines of up to 15 km is now possible, and opens up new
parameter space for submm astronomy. <P />.
---------------------------------------------------------
Title: Three-dimensional simulations of core-collapse supernovae:
from shock revival to shock breakout
Authors: Wongwathanarat, A.; Müller, E.; Janka, H. -Th.
2015A&A...577A..48W Altcode: 2014arXiv1409.5431W
We present three-dimensional hydrodynamic simulations of the evolution
of core-collapse supernovae (SN) from blast-wave initiation by
the neutrino-driven mechanism to shock breakout from the stellar
surface, using an axis-free Yin-Yang grid and considering two 15
M<SUB>⊙</SUB> red supergiants (RSG) and two blue supergiants
(BSG) of 15 M<SUB>⊙</SUB> and 20 M<SUB>⊙</SUB>. We demonstrate
that the metal-rich ejecta in homologous expansion still carry
fingerprints of asymmetries at the beginning of the explosion, but
the final metal distribution is massively affected by the detailed
progenitor structure. The most extended and fastest metal fingers and
clumps are correlated with the biggest and fastest-rising plumes of
neutrino-heated matter, because these plumes most effectively seed the
growth of Rayleigh-Taylor (RT) instabilities at the C+O/He and He/H
composition-shell interfaces after the passage of the SN shock. The
extent of radial mixing, global asymmetry of the metal-rich ejecta,
RT-induced fragmentation of initial plumes to smaller-scale fingers,
and maximum Ni and minimum H velocities depend not only on the initial
asphericity and explosion energy (which determine the shock and initial
Ni velocities), but also on the density profiles and widths of C+O
core and He shell and on the density gradient at the He/H transition,
which leads to unsteady shock propagation and the formation of reverse
shocks. Both RSG explosions retain a large global metal asymmetry
with pronounced clumpiness and substructure, deep penetration of Ni
fingers into the H-envelope (with maximum velocities of 4000-5000
km s<SUP>-1</SUP> for an explosion energy around 1.5 bethe) and
efficient inward H-mixing. While the 15 M<SUB>⊙</SUB> BSG shares
these properties (maximum Ni speeds up to ~3500 km s<SUP>-1</SUP>),
the 20 M<SUB>⊙</SUB> BSG develops a much more roundish geometry
without pronounced metal fingers (maximum Ni velocities only ~2200 km
s<SUP>-1</SUP>) because of reverse-shock deceleration and insufficient
time for strong RT growth and fragmentation at the He/H interface.
---------------------------------------------------------
Title: Erratum: “The Herschel Inventory of the Agents of Galaxy
Evolution (Heritage) in the Magellanic Clouds, a Herschel Open
Time Key Program” <A href="/abs/2013AJ....146...62M">(2013, AJ,
146, 62)</A>
Authors: Meixner, M.; Panuzzo, P.; Roman-Duval, J.; Engelbracht, C.;
Babler, B.; Seale, J.; Hony, S.; Montiel, E.; Sauvage, M.; Gordon,
K.; Misselt, K.; Okumura, K.; Chanial, P.; Beck, T.; Bernard, J. -P.;
Bolatto, A.; Bot, C.; Boyer, M. L.; Carlson, L. R.; Clayton, G. C.;
Chen, C. -H. R.; Cormier, D.; Fukui, Y.; Galametz, M.; Galliano, F.;
Hora, J. L.; Hughes, A.; Indebetouw, R.; Israel, F. P.; Kawamura, A.;
Kemper, F.; Kim, S.; Kwon, E.; Lebouteiller, V.; Li, A.; Long, K. S.;
Madden, S. C.; Matsuura, M.; Muller, E.; Oliveira, J. M.; Onishi,
T.; Otsuka, M.; Paradis, D.; Poglitsch, A.; Reach, W. T.; Robitaille,
T. P.; Rubio, M.; Sargent, B.; Sewiło, M.; Skibba, R.; Smith, L. J.;
Srinivasan, S.; Tielens, A. G. G. M.; van Loon, J. Th.; Whitney, B.
2015AJ....149...88M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Modulating magnetar emission by magneto-elastic oscillations
Authors: Gabler, M.; Cerdá-Durán, P.; Font, J. A.; Stergioulas,
N.; Müller, E.
2014AN....335..240G Altcode:
We present a new numerical tool to calculate the emission of highly
magnetized neutron stars (magnetars) and apply it to describe the
quasi-periodic oscillations (QPOs) observed in magnetar giant flares. In
previous work we have developed a model of magneto-elastic oscillations
of magnetars that allows to reproduce the observed frequencies. These
QPOs can couple to the star's exterior through the magnetic field and
induce currents in the magnetosphere that provide scattering targets
for resonant cyclotron scattering of the photons. The scattering is
calculated with a Monte-Carlo approach and it is coupled to a code
that calculates the momentum distribution of the charge carriers as an
one-dimensional accelerator problem. As a first test of the method we
calculate the modulation of the quiescent emission of the neutron star
by the magneto-elastic QPOs for a prescribed momentum distribution of
the charge carriers. The necessary amplitudes of the QPOs at the surface
of the star to modulate the emission significantly are {⪉ 1} km.
---------------------------------------------------------
Title: Hydrodynamic simulations of the interaction of supernova shock
waves with a clumpy environment: the case of the RX J0852.0-4622
(Vela Jr) supernova remnant
Authors: Obergaulinger, M.; Iyudin, A. F.; Müller, E.; Smoot, G. F.
2014MNRAS.437..976O Altcode: 2013MNRAS.tmp.2632O; 2014arXiv1408.0895O
Observations in all electromagnetic bands show that many supernova
remnants (SNRs) have a very aspherical shape. This can be the result
of asymmetries in the supernova explosion or a clumpy circumstellar
medium. We study the generation of inhomogeneities and the mixing
of elements arising from these two sources in multidimensional
hydrodynamic simulations of the propagation of a supernova blast
wave into a cloudy environment. We model a specific SNR, Vela Jr
(RX J0852.0-4622). By comparing our results with recent observations,
we can constrain the properties of the explosion. We find that a very
energetic explosion of several 10<SUP>51</SUP> erg occurring roughly
about 800 years ago is consistent with the shape and emission of the
SNR, as well as a supernova with an energy closer to the canonical
value of 10<SUP>51</SUP> erg a few thousand years ago.
---------------------------------------------------------
Title: MALT90: The Millimetre Astronomy Legacy Team 90 GHz Survey
Authors: Jackson, J. M.; Rathborne, J. M.; Foster, J. B.; Whitaker,
J. S.; Sanhueza, P.; Claysmith, C.; Mascoop, J. L.; Wienen, M.;
Breen, S. L.; Herpin, F.; Duarte-Cabral, A.; Csengeri, T.; Longmore,
S. N.; Contreras, Y.; Indermuehle, B.; Barnes, P. J.; Walsh, A. J.;
Cunningham, M. R.; Brooks, K. J.; Britton, T. R.; Voronkov, M. A.;
Urquhart, J. S.; Alves, J.; Jordan, C. H.; Hill, T.; Hoq, S.;
Finn, S. C.; Bains, I.; Bontemps, S.; Bronfman, L.; Caswell, J. L.;
Deharveng, L.; Ellingsen, S. P.; Fuller, G. A.; Garay, G.; Green,
J. A.; Hindson, L.; Jones, P. A.; Lenfestey, C.; Lo, N.; Lowe, V.;
Mardones, D.; Menten, K. M.; Minier, V.; Morgan, L. K.; Motte, F.;
Muller, E.; Peretto, N.; Purcell, C. R.; Schilke, P.; Bontemps,
Schneider-N.; Schuller, F.; Titmarsh, A.; Wyrowski, F.; Zavagno, A.
2013PASA...30...57J Altcode: 2013arXiv1310.1131J
The Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey aims
to characterise the physical and chemical evolution of high-mass
star-forming clumps. Exploiting the unique broad frequency range and
on-the-fly mapping capabilities of the Australia Telescope National
Facility Mopra 22 m single-dish telescope <SUP>1</SUP> , MALT90 has
obtained 3' × 3' maps towards ~2 000 dense molecular clumps identified
in the ATLASGAL 870 μm Galactic plane survey. The clumps were selected
to host the early stages of high-mass star formation and to span
the complete range in their evolutionary states (from prestellar,
to protostellar, and on to H II regions and photodissociation
regions). Because MALT90 mapped 16 lines simultaneously with excellent
spatial (38 arcsec) and spectral (0.11 km s<SUP>-1</SUP>) resolution,
the data reveal a wealth of information about the clumps' morphologies,
chemistry, and kinematics. In this paper we outline the survey strategy,
observing mode, data reduction procedure, and highlight some early
science results. All MALT90 raw and processed data products are
available to the community. With its unprecedented large sample of
clumps, MALT90 is the largest survey of its type ever conducted and
an excellent resource for identifying interesting candidates for
high-resolution studies with ALMA.
---------------------------------------------------------
Title: The HERSCHEL Inventory of The Agents of Galaxy Evolution in
the Magellanic Clouds, a Herschel Open Time Key Program
Authors: Meixner, M.; Panuzzo, P.; Roman-Duval, J.; Engelbracht, C.;
Babler, B.; Seale, J.; Hony, S.; Montiel, E.; Sauvage, M.; Gordon,
K.; Misselt, K.; Okumura, K.; Chanial, P.; Beck, T.; Bernard, J. -P.;
Bolatto, A.; Bot, C.; Boyer, M. L.; Carlson, L. R.; Clayton, G. C.;
Chen, C. -H. R.; Cormier, D.; Fukui, Y.; Galametz, M.; Galliano, F.;
Hora, J. L.; Hughes, A.; Indebetouw, R.; Israel, F. P.; Kawamura, A.;
Kemper, F.; Kim, S.; Kwon, E.; Lebouteiller, V.; Li, A.; Long, K. S.;
Madden, S. C.; Matsuura, M.; Muller, E.; Oliveira, J. M.; Onishi,
T.; Otsuka, M.; Paradis, D.; Poglitsch, A.; Reach, W. T.; Robitaille,
T. P.; Rubio, M.; Sargent, B.; Sewiło, M.; Skibba, R.; Smith, L. J.;
Srinivasan, S.; Tielens, A. G. G. M.; van Loon, J. Th.; Whitney, B.
2013AJ....146...62M Altcode:
We present an overview of the HERschel Inventory of The Agents of
Galaxy Evolution (HERITAGE) in the Magellanic Clouds project, which
is a Herschel Space Observatory open time key program. We mapped the
Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) at 100,
160, 250, 350, and 500 μm with the Spectral and Photometric Imaging
Receiver (SPIRE) and Photodetector Array Camera and Spectrometer (PACS)
instruments on board Herschel using the SPIRE/PACS parallel mode. The
overriding science goal of HERITAGE is to study the life cycle of
matter as traced by dust in the LMC and SMC. The far-infrared and
submillimeter emission is an effective tracer of the interstellar
medium (ISM) dust, the most deeply embedded young stellar objects
(YSOs), and the dust ejected by the most massive stars. We describe
in detail the data processing, particularly for the PACS data, which
required some custom steps because of the large angular extent of a
single observational unit and overall the large amount of data to be
processed as an ensemble. We report total global fluxes for the LMC
and SMC and demonstrate their agreement with measurements by prior
missions. The HERITAGE maps of the LMC and SMC are dominated by the ISM
dust emission and bear most resemblance to the tracers of ISM gas rather
than the stellar content of the galaxies. We describe the point source
extraction processing and the criteria used to establish a catalog for
each waveband for the HERITAGE program. The 250 μm band is the most
sensitive and the source catalogs for this band have ~25,000 objects for
the LMC and ~5500 objects for the SMC. These data enable studies of ISM
dust properties, submillimeter excess dust emission, dust-to-gas ratio,
Class 0 YSO candidates, dusty massive evolved stars, supernova remnants
(including SN1987A), H II regions, and dust evolution in the LMC and
SMC. All images and catalogs are delivered to the Herschel Science
Center as part of the community support aspects of the project. These
HERITAGE images and catalogs provide an excellent basis for future
research and follow up with other facilities.
---------------------------------------------------------
Title: The CoCoNuT code: from neutron star oscillations to supernova
explosions
Authors: Cerdá-Durán, P.; Gabler, M.; Müller, E.; Font, J. A.;
Stergioulas, N.; Obergaulinger, M.; Aloy, M. A.; DeBrye, N.;
Cordero-Carrión, I.; Ibáñez, J. M.
2013hsa7.conf..940C Altcode:
CoCoNuT is a numerical code, that evolves the General relativistic
magneto-hydrodynamics equations coupled to the Einstein equations in
the CFC approximation. Its main purpose is to simulate astrophysical
scenarios in which strong gravity is important such as the collapse
of massive stars and the evolution of neutron stars. I review recent
results of the numerical code regarding neutron star oscillations and
core collapse supernova and its observational consequences.
---------------------------------------------------------
Title: Modulating magnetar emission by magneto-elastic oscillations
Authors: Gabler, M.; Cerdá-Durán, P.; Font, J.; Stergioulas, N.;
Müller, E.
2013ffep.confE..23G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Three-dimensional neutrino-driven supernovae: Neutron star
kicks, spins, and asymmetric ejection of nucleosynthesis products
Authors: Wongwathanarat, A.; Janka, H. -Th.; Müller, E.
2013A&A...552A.126W Altcode: 2012arXiv1210.8148W
We present three-dimensional (3D) simulations of supernova explosions of
nonrotating stars, triggered by the delayed neutrino-heating mechanism
with a suitable choice of the core-neutrino luminosity. Our results show
that asymmetric mass ejection caused by hydrodynamic instabilities can
accelerate the neutron star (NS) up to recoil velocities of more than
700 km s<SUP>-1</SUP> by the "gravitational tug-boat mechanism", which
is sufficient to explain most observed pulsar space velocities. The
associated NS spin periods for our nonrotating progenitors are about
100 ms to 8000 ms without any obvious correlation between spin and
kick magnitudes or directions. This suggests that faster spins and a
possible spin-kick alignment might require angular momentum in the
progenitor core prior to collapse. Our simulations for the first
time demonstrate a clear correlation between the size of the NS
kick and anisotropic production and distribution of heavy elements
created by explosive burning behind the shock. In the case of large
pulsar kicks, the explosion is significantly stronger opposite to the
kick vector. Therefore the bulk of the explosively fused iron-group
elements, in particular nickel, are ejected mostly in large clumps
against the kick direction. This contrasts with the case of low
recoil velocity, where the nickel-rich lumps are more isotropically
distributed. Explosively produced intermediate-mass nuclei heavier
than <SUP>28</SUP>Si (like <SUP>40</SUP>Ca and <SUP>44</SUP>Ti) also
exhibit significant enhancement in the hemisphere opposite to the
direction of fast NS motion, while the distribution of <SUP>12</SUP>C,
<SUP>16</SUP>O, and <SUP>20</SUP>Ne is not affected, and that of
<SUP>24</SUP>Mg only marginally. Mapping the spatial distribution of the
heavy elements in supernova remnants with identified pulsar motion may
offer an important diagnostic test of the kick mechanism. Unlike kick
scenarios based on anisotropic neutrino emission, our hydrodynamical
acceleration model predicts enhanced ejection of iron-group elements and
of their nuclear precursors in the opposite direction to the NS recoil.
---------------------------------------------------------
Title: Resolved Schmidt-Kennicutt Relation for Star Forming Regions
in the Galaxy and Magellanic Clouds
Authors: Chen, C. -H. R.; Indebetouw, R.; Muller, E.; Messineo, M.;
Menten, K. M.; SAGE-SMC Team
2013IAUS..292..307C Altcode:
The relationship between star formation rate (SFR) and the gas surface
density (Σ<SUB>gas</SUB>) is one of the most critical links between
star formation and galaxy evolution. The observed SFR- Σ<SUB>gas</SUB>
relation, the "Schmidt-Kennicutt (S-K) law", is tight when properties
are averaged over kpc, but breaks down at the scale of giant molecular
clouds (GMCs). To understand the physics governing the variations at GMC
scales and the tight correlation at kpc scales, spatially and temporally
resolved data covering a wide range of linear scale are needed. We have
used the Spitzer surveys of the Large Magellanic Cloud and Magellanic
Bridge to identify massive young stellar objects (YSOs), estimate
"instantaneous" SFRs, and compare them to the S-K relation. These
instantaneous SFRs are further compared to that estimated from
integrated Hα and 24 μm luminosities to examine how SFRs vary on
10 Myr timescales. We have also used SINFONI near-IR integral field
spectra of two Galactic mini-starbursts W31 and W43 to determine their
underlying massive stellar content, estimate the SFRs, and compare to
the S-K relation. To investigate evironmental effects on star formation,
we have used complete YSO samples in the LMC and the Bridge to estimate
global star formation efficiencies (SFE) in these two systems.
---------------------------------------------------------
Title: Comet 168P/Hergenrother
Authors: Hergenrother, C. W.; Mueller, E. A.; Sekanina, Z.
2012CBET.3318....1H Altcode:
Carl W. Hergenrother, Lunar and Planetary Laboratory, University of
Arizona, reports the detection of an additional companion (denoted G)
to those announced on CBET 3295. Co-added R-band images were obtained
with the Kitt Peak 2.1-m reflector by Yanga Fernandez and Emily Kramer
(University of Central Florida); the data were made available by
Beatrice E. A. Mueller (Planetary Science Institute). Companion G
was detected at the following separations and position angles from
the central condensation of the primary: Nov. 11.35 UT, 9".7, 168.0
deg; Nov. 12.29, 9".8, 163.9 deg. On Nov. 11.35, the companion was
diffuse with no apparent central condensation and elongated towards the
anti-solar direction with dimensions of 2".4 by 1".8. On Nov. 12.29,
the companion appeared fainter, with dimensions of 1".8 x 1".5,
elongated towards the anti-solar direction. Z. Sekanina, Jet Propulsion
Laboratory, reports that the motion of this additional fragment G
is consistent with the separation from the primary nucleus A at the
beginning of September, with a very low velocity of about 0.1 m/s. The
fragment was subjected to a nongravitational deceleration of 15 +/-
1 units of 10**-5} solar attraction. Although the accuracy of the
results is not high, it appears that this is the only fragment whose
separation dates back to the first outburst and must have survived
for at least 10 weeks. In terms of the nongravitational deceleration,
this is the only fragment that rivals fragment B. Predicted separation
distances of component G from component A and position angles at 0 h
ET: Nov. 29, 12".0, 167 deg; Dec. 9, 12".8, 170 deg; Dec. 19, 13".2,
176 deg; Dec. 29, 13".5, 183 deg.
---------------------------------------------------------
Title: Giant Molecular Clouds and Star Formation in the Tidal
Molecular Arm of NGC 4039
Authors: Espada, D.; Komugi, S.; Muller, E.; Nakanishi, K.; Saito,
M.; Tatematsu, K.; Iguchi, S.; Hasegawa, T.; Mizuno, N.; Iono, D.;
Matsushita, S.; Trejo, A.; Chapillon, E.; Takahashi, S.; Su, Y. N.;
Kawamura, A.; Akiyama, E.; Hiramatsu, M.; Nagai, H.; Miura, R. E.;
Kurono, Y.; Sawada, T.; Higuchi, A. E.; Tachihara, K.; Saigo, K.;
Kamazaki, T.
2012ApJ...760L..25E Altcode: 2012arXiv1211.0767E
The properties of tidally induced arms provide a means to study
molecular cloud formation and the subsequent star formation under
environmental conditions which, in principle, are different from
quasi-stationary spiral arms. We report the properties of a newly
discovered molecular gas arm of likely tidal origin at the south
of NGC 4039 and the overlap region in the Antennae galaxies,
with a resolution of 1farcs68 × 0farcs85, using the Atacama
Large Millimeter/submillimeter Array science verification CO(2-1)
data. The arm extends 3.4 kpc (34”) and is characterized by
widths of lsim200 pc (2”) and velocity widths of typically ΔV ~=
10-20 km s<SUP>-1</SUP>. About 10 clumps are strung out along this
structure, most of them unresolved, with average surface densities
of Σ<SUB>gas</SUB> ~= 10-100 M <SUB>⊙</SUB> pc<SUP>-2</SUP>, and
masses of (1-8)×10<SUP>6</SUP> M <SUB>⊙</SUB>. These structures
resemble the morphology of beads on a string, with an almost equidistant
separation between the beads of about 350 pc, which may represent a
characteristic separation scale for giant molecular associations. We
find that the star formation efficiency at a resolution of 6”(600 pc)
is in general a factor of 10 higher than in disk galaxies and other
tidal arms and bridges. This arm is linked, based on the distribution
and kinematics, to the base of the western spiral arm of NGC 4039,
but its morphology is different to that predicted by high-resolution
simulations of the Antennae galaxies.
---------------------------------------------------------
Title: Comet 168P/Hergenrother
Authors: Mueller, E. A.; Stevenson, R. A.; Bauer, J. M.; Masiero,
J. R.; Mainzer, A. K.; Sekanina, Z.; Sostero, G.; Hergenrother, C. W.
2012CBET.3295....5M Altcode:
Hergenrother also reports four separate companions to 168P observed in
data taken between Oct. 26.42 and Nov. 8.29 UT. The data for all dates
from the Kitt Peak 2.1-m reflector were obtained by Yanga Fernandez and
Emily Kramer and made available by Beatrice E. A. Mueller. Data from
the Faulkes 2.0-m reflector were obtained by Sostero et al. (see above)
on Oct. 26, by the Dollar Academy and Queen's College on Nov. 2, and
by the Maui Community College on Nov. 3 as part of Faulkes Telescope
Education project. Date UT P.A. Sep. Comp. Telescope/ 2012 (deg) (")
measurer Oct. 26.42 191.1 2.1 B Faulkes/Hergenrother Nov. 2.44 167.4 3.3
B Faulkes/Hergenrother 3.28 165.3 3.1 B Faulkes/Hergenrother 6.28 160.9
3.3 B Faulkes/Hergenrother 6.30 164.8 3.6 B Kitt Peak/Hergenrother
7.30 162.4 3.6 B Kitt Peak/Hergenrother 7.32 165.6 3.5 B Kitt
Peak/Hergenrother Oct. 26.42 139.8 3.8 C Faulkes/Hergenrother Nov. 2.44
133.7 5.8 C Faulkes/Hergenrother 3.28 131.7 6.4 C Faulkes/Hergenrother
Nov. 2.44 159.3 5.2 E Kitt Peak/Hergenrother 3.28 151.0 5.0 E Kitt
Peak/Hergenrother 7.31 159.1 6.0 E Kitt Peak/Hergenrother 8.27 164.0
5.7 E Kitt Peak/Hergenrother 8.29 165.3 5.7 E Kitt Peak/Hergenrother
Nov. 6.28 148.3 9.1 F Kitt Peak/Hergenrother 6.30 149.1 9.3 F
Kitt Peak/Hergenrother 7.31 143.9 9.5 F Kitt Peak/Hergenrother
R. A. Stevenson, J. M. Bauer, J. R. Masiero, and A. K. Mainzer, Jet
Propulsion Laboratory, report CCD observations of comet 168P taken
from the Gemini-North telescope atop Mauna Kea, Hawaii, following the
report by Sostero et al. (see above) of the outburst and detection
of a fragement on Oct. 26.4 UT. Fragment B was detected 2".4 from the
primary nuclear condensation on Oct. 28.4 at a position angle of 172.9
deg using 10-s exposures; the brightness of the fragment is 29 percent
of the brightest region, which is presumed to be the location of the
nucleus. Two additional fragments were detected in 30-s (unstacked)
exposures taken on Nov. 2.3: Fragment B was detected 2".9 from the
primary nuclear condensation at a position angle of 162.5 deg, with a
relative brightness of 27 percent with respect to the nucleus-centered
region. Fragment C was detected 6".2 from the nucleus- centered region
at a position angle of 132.1 deg with a brightness of 25 percent
relative to the nucleus-centered region. Fragment D was detected 11".4
from the nuclear condensation at a position angle of 145.1 deg with a
relative brightness of 9 percent to the nucleus-centered region. All
fragments appear diffuse and without central condensations. Brightnesses
were measured using sky-subtracted aperture photometry; apertures
were 1".022 in radius (with projected on-sky radii of 399 and 422 km
for Oct. 28 and Nov. 2, respectively). Fragment B is separating from
the primary nuclear condensation with a projected on-sky velocity of
0.6 +/- 0.1 m/s (1-sigma uncertainty), measured using r-band (630 nm)
data from the 8-m Gemini-North telescope (Oct. 28.4 and Nov. 2.3)
and J-band (1.25-micron) and H-band (1.651-micron) images from the
3.5-m WIYN telescope (Oct. 29.2, 30.1, and Nov. 1.1). Z. Sekanina,
Jet Propulsion Laboratory, reports that four of the five companions
apparently broke off from the primary nucleus A. Based on 9 offsets
from Oct. 26-Nov. 7, companion B was found to have separated on
Sept. 17.5 +/- 2.5 UT with a velocity of 0.18 +/- 0.05 m/s and was
subjected to a nongravitational deceleration of 15 +/- 3 units of
10**-5} solar attraction. Very similar solutions were obtained on
the assumption that the separation of B coincided with the onset of
an outburst on Sept. 22. For companion C, from four offsets between
Oct. 26 and Nov. 3, Sekanina derived a separation on Oct. 7.0 +/-
1.5 UT, with a velocity of 0.3 +/- 0.1 m/s, and a deceleration of
53 +/- 12 units. Very similar solutions resulted assuming that the
separation of C coincided with the onset of another outburst, on October
1. For companion D, the offset from Nov. 2 gave only very approximate
parameters, a separation around Sept. 28 (probably coinciding with
the same outburst as the separation of C) and a deceleration of 70
units. Companion E does not appear to have derived from A, but it may
have split off from B within days after B broke off from A. Companion
F was found to have separated from A on Sept. 24 (again at about the
time of the outburst of Sept. 22) and was subjected to a deceleration
of about 40 units. As the mass of material moved in the direction in
which fragment C also appeared, and fragment C split off around the
time of the Oct. 1 outburst, the mass of material was also a product of
that same outburst. The apparent tendency of some companions to grow
elongated with time suggests that they already represent clusters of
subfragments subjected to a range of decelerations, thus entering an
advanced phase of disintegration. Because all the companions appear
to be short-lived (as also implied by their high decelerations), the
following ephemerides are terminated by the end of November. Predicted
separation distances from nucleus A and position angles at 0h ET:
Nov. 9, 3".9, 163 deg (B); 8".4, 133 deg (C); 15".2, 144 deg (D); 6".1,
159 deg (E); 10".1, 147 deg (F); Nov. 19, 5".2, 160 deg (B); 12".0,
133 deg (C); 20".6, 144 deg (D); 8".0, 157 deg (E); 13".4, 146 deg
(F); Nov. 29, 6".2, 161 deg (B); 15".1, 135 deg (C); 25".0, 146 deg
(D); 9".5, 158 deg (E); 16'.0, 148 deg (F).
---------------------------------------------------------
Title: On multigrid solution of the implicit equations of
hydrodynamics. Experiments for the compressible Euler equations in
general coordinates
Authors: Kifonidis, K.; Müller, E.
2012A&A...544A..47K Altcode:
<BR /> Aims: We describe and study a family of new multigrid
iterative solvers for the multidimensional, implicitly discretized
equations of hydrodynamics. Schemes of this class are free of the
Courant-Friedrichs-Lewy condition. They are intended for simulations
in which widely differing wave propagation timescales are present. A
preferred solver in this class is identified. Applications to some
simple stiff test problems that are governed by the compressible Euler
equations, are presented to evaluate the convergence behavior, and the
stability properties of this solver. Algorithmic areas are determined
where further work is required to make the method sufficiently efficient
and robust for future application to difficult astrophysical flow
problems. <BR /> Methods: The basic equations are formulated and
discretized on non-orthogonal, structured curvilinear meshes. Roe's
approximate Riemann solver and a second-order accurate reconstruction
scheme are used for spatial discretization. Implicit Runge-Kutta
(ESDIRK) schemes are employed for temporal discretization. The resulting
discrete equations are solved with a full-coarsening, non-linear
multigrid method. Smoothing is performed with multistage-implicit
smoothers. These are applied here to the time-dependent equations
by means of dual time stepping. <BR /> Results: For steady-state
problems, our results show that the efficiency of the present
approach is comparable to the best implicit solvers for conservative
discretizations of the compressible Euler equations that can be
found in the literature. The use of red-black as opposed to symmetric
Gauss-Seidel iteration in the multistage-smoother is found to have only
a minor impact on multigrid convergence. This should enable scalable
parallelization without having to seriously compromise the method's
algorithmic efficiency. For time-dependent test problems, our results
reveal that the multigrid convergence rate degrades with increasing
Courant numbers (i.e. time step sizes). Beyond a Courant number of
nine thousand, even complete multigrid breakdown is observed. Local
Fourier analysis indicates that the degradation of the convergence rate
is associated with the coarse-grid correction algorithm. An implicit
scheme for the Euler equations that makes use of the present method
was, nevertheless, able to outperform a standard explicit scheme on
a time-dependent problem with a Courant number of order 1000. <BR />
Conclusions: For steady-state problems, the described approach enables
the construction of parallelizable, efficient, and robust implicit
hydrodynamics solvers. The applicability of the method to time-dependent
problems is presently restricted to cases with moderately high Courant
numbers. This is due to an insufficient coarse-grid correction of the
employed multigrid algorithm for large time steps. Further research
will be required to help us to understand and overcome the observed
multigrid convergence difficulties for time-dependent problems.
---------------------------------------------------------
Title: Magneto-elastic Oscillations and Magnetar QPOs
Authors: Stergioulas, N.; Gabler, M.; Cerdá-Durán, P.; Font, J. A.;
Müller, E.
2012ASPC..459..167S Altcode:
The origin of the quasi-periodic oscillations (QPOs) observed
in the giant flares of soft gamma-ray repeaters (SGRs) remains
uncertain. Current models explore the idea that long-term quasi-periodic
oscillations are trapped at the turning points of the continuum of
torsional magneto-elastic oscillations in the magnetar's interior. After
reviewing recent work in this field, we describe our latest efforts
using two-dimensional, general-relativistic, magneto-hydrodynamical
simulations, coupled to evolutions of shear waves in the solid crust,
in order to explore the viability of this model when a purely dipolar
magnetic field is assumed. We demonstrate the existence of three
different regimes (a) B < 5 × 10<SUP>13</SUP> G, where crustal shear
modes dominate the evolution; (b) 5 × 10<SUP>13</SUP> G < B <
10<SUP>15</SUP> G, where Alfvén QPOs are mainly confined to the core
of the star and the crustal shear modes are damped very efficiently;
and (c) B > 10<SUP>15</SUP> G, where magneto-elastic oscillations
reach the surface and approach the behavior of purely Alfvén QPOs. Our
results do not leave much room for a crustal-mode interpretation of
observed QPOs in SGR giant flares, in the case of a purely dipolar
magnetic field. On the other hand, the observed QPOs could originate
from Alfvén-like, global, turning-point QPOs in models with dipolar
magnetic field strengths in the narrow range of 5 × 10<SUP>15</SUP> G
≤ B ≤ 1.4 × 10<SUP>16</SUP> G. To agree with estimates for magnetic
field strengths in known magnetars, a more complicated magnetic field
structure or superfluidity of the neutrons and superconductivity of
the protons should be taken into account.
---------------------------------------------------------
Title: Three-dimensional Core-Collapse Supernova Simulations on the
Yin-Yang Grid
Authors: Wongwathanarat, A.; Janka, H.; Müller, E.
2012ASPC..453...95W Altcode:
We perform a set of neutrino-driven core collapse supernova simulations
in three dimensions studying the hydrodynamical neutron star (NS) kick
mechanism. The computational cost is reduced significantly with the help
of an axis-free overlapping grid technique in spherical geometry called
the “Yin-Yang” grid. Our simulations follow the evolution of core
collapse supernovae from 15 ms after bounce until approximately 1.4
s later. For the first time in three dimensions, our results produce
neutron star kick velocities up to ∼600 km/s. Such a high kick
velocity results from the highly asymmetric mass distribution in the
post-shock region exerting a net gravitational pull on the proto-neutron
star on a timescale of a few seconds. With this kick scenario proposed
by Scheck et al., NS recoil velocities larger than ∼1000 km/s might
as well be possible but require a larger set of models for statistical
reasons (connected with the stochastic development of asymmetries). Our
simulations also confirm an enhanced production of heavy elements
in the direction roughly opposite to the NS recoil direction. This
produces a detectable hemispheric asymmetry in the distribution of
heavy elements which can be used to constrain the NS kick mechanism.
---------------------------------------------------------
Title: 2012 LT7 = 2009 MH1
Authors: Fuse, T.; Miyazaki, S.; Spencer, J. R.; Tholen, D. J.;
Toshida, F.; Buie, M. W.; Borncamp, D. M.; Gay, P. L.; Wasserman,
L. H.; Karoji, H.; Kinoshita, D.; Yanagisawa, T.; Furusawa, H.;
Yoshida, F.; Yamashida, T.; Tajitsu, A.; Little, P.; McMahon, C.; Lee,
A.; Scheulen, F.; Sauro, C.; Robinson, C.; Berry, S.; Abbate, T.;
Abrahamson, T.; Adam, M.; Adamson, J.; Agbedor, A.; Alexander, B.;
Allan, U.; Alldredge, X.; Allen, A. M. H.; Alton, D.; Alves, M. P.;
Alves, V. S.; Amerongen, O.; Anderson, W. L.; Andrews, J.; Anstett,
M.; Applebaum, K.; Arrington, J.; Ashton, E. T. F.; Astl, W.; Atkins,
L. G.; Badker, K.; Badnaruk, B.; Baeten, E.; Bailey, R. C.; Balick,
R.; Ball, J. L.; Barnett, B. E.; Bartel, J. S.; Bartholomew, C.;
Baumgaertner, P.; Becker, A.; Bedard, E.; Beer, I.; Begg, J.; Begonja,
J.; Bel, P.; Bevc, J.; Bezugly, V. A.; Bianchini, G.; Biel, M.;
Bigelow, B.; Billiani, M.; Bishop, J.; Blanaru, M. C.; Blystone, S.;
Boden, G.; Boesch, T.; Bohnes, R.; Boland, C.; Bomeny, F.; Borck, J.;
Boschat, M.; Boscher, G. P. A.; Boutilier, M. A.; Boyd, S.; Bradford,
N. B.; Bratcher, S.; Brayshaw, P.; Brinkmann, A.; Brittain, C.; Brogan,
D.; Brooks, R.; Browne, D.; Brydon, T.; Burluraux, D.; Butler, C.;
Caado, P.; Cairns, N. G.; Callebout, F.; Cameron, D.; Campbell, P.;
Campos, J.; Candeias, J.; Caracciolo, A.; Carlino, S.; Carpenter, A.;
Carrascal, C.; Carruthers, J.; Carsenty, U.; Castro, F.; Chadwick,
L. D.; Chaghafi, E.; Chamberlain, B.; Champion, K.; Chandler, C.;
Cheng, J. K. H.; Chestnov, D.; Chinery, C.; Chisholm, J.; CIvinskas,
A.; Clark, A.; Cleaver, D.; Cline, M.; Clingenpeel, S.; Collins, B.;
Conseil, E.; Corfield, S.; Costello, R.; Costin, R.; Cotton, M.;
Craddock, C.; Crosio, M.; Cross, J. A.; Crossland, B.; Crowe, C.;
Cruze, S.; Damerell-Moss, R.; Danker, J.; Darcy, M.; David, G.; Dawey,
J. M. A.; De A Barreto, V. P.; De Grandis, C.; de Vries, D.; de Witt,
S.; Dekker, K.; Delille, S.; Demers, J.; Dether, A.; Devine, K.; Dias,
W. A.; Diecks, S.; Dimitrova, E.; Doll, K. M.; Dowden, P.; Duggan,
P. N.; Dumitriu, A.; Duncan, L. M.; Dungworth, G.; Dunlea, P.; Dzierwa,
D.; Edwards, A.; Elidoro, C.; Ellinger, P.; Elsnau, L. J.; Elustondo,
M.; Emery, Y. A.; Evans, H. F.; Evans, J.; Evdokimova, S.; Eve, A.;
Fakahany, A.; Farmer, A.; Farrelly, K.; Fazekas, P.; Felsenstein,
A.; Fequet, N.; Finney, S.; Fisher, T.; Fletcher, M. S.; Flippo,
K.; Fonseca, J. P. B.; Foote, C.; Fox, K.; Fromm, D. C.; Fronczak,
S.; Fuchs, R.; Fukushi, H.; Furskog, M.; Gaebel, M.; Gagliano, R.;
Gash, D.; Ghegoiu, S.; Gilbert, B.; Gilbertson, J.; Gill, R.; Gillis,
A.; Glover, R.; Gonano, V.; Gonzaga, S.; Goodman, S. J.; Gorton,
A.; Goznell, L.; Grady, H.; Green, T.; Greutmann, P.; Griffing, C.;
Gronowski, P.; Guerreiro, R.; Gutierrez Gomez, E.; Gutler, D.; Guttau,
C.; Gwenn, P.; Gyarmati, L.; Hackl, L.; Hager, T.; Hall, E.; Haller,
J.; Hantel, T.; Harkin, J.; Harlander, A.; Hartel, C.; Hartmeijer,
E.; Harvey, R. F.; Hatwood, A.; Heikes, R.; Heilman, H.; Helk, F.;
Helmersen, E.; Hendricks, R.; Hennessey, S.; Hensley, B.; Herentrey,
B.; Herr, M.; Herridge, J.; Higgins, J. F.; Hignell, S.; Hodge, T.;
Hoffman, T.; Hollerung, T.; Horvath, T.; Hrdlicka, D.; Huefner, M.;
Huerta-Martin, A. E.; Hughes, P.; Hui, M. -T.; Hunt, C.; Hutchinson,
C.; Ihle, N.; Imp, B.; Ivanchenko, S.; Izakovic, K.; Jackson, P.;
Jammer, W.; Jamulla, J. D.; Janssen, N.; Jaureguiberry, A.; Jaworski,
D.; Jennings, P.; Jewell, R.; Johnson, W.; Jones, L. F.; Kaczmarek,
S. L.; Kaczmarowski, A.; Kaluzny, M.; Kaminski, N.; Kamp, M.; Kanegae,
K.; Karge, S.; Karl, A.; Karthikeyan, D.; Kastengren, A.; Kavalli, S.;
Kaylor, N.; Kelly, B.; Kendall, C.; Kennedy, A.; Kerr, B.; Kidner,
S.; Kidulich, M.; King, R.; Kirschenmann, B.; Klouwen, J. H.; Klug,
K.; Koester, K.; Kolling, M.; Korber, R.; Kostrzewa, P.; Kracht, R.;
Krawczyk, H.; Krikken, R.; Krol, P.; Kumar, H.; Kumrucu-Lohmiller, M.;
Kyriakides, P.; Lactin, D. J.; Lamperti, A.; Lander, J.; Larson, M.;
Laurentiu, F.; Le Garff, C.; Le Gendre, P.; Le Tourneau, K.; Ledin,
P.; Leegwater, D. V.; Lenke, N.; Leon, P. A.; Levin, A. V.; Lindberg,
D.; Lipinski, J.; Lloyd, C.; Loeffler, V. P., III; Lopez-Fabrega,
R.; Luchinat, E.; Luers, S.; Lummus, J.; Lunn, P. J.; Lysiak, A.;
Macmillan, C.; Macumber, A.; Madala, R.; Madsen, K. L. P.; Magee, S.;
Maherjinqiu, R.; Mangili, C.; Mankevich, A.; Manning, B.; Marion, D.;
Martin, A.; Martinez, D.; Martins, J. A.; Massuda, M. H.; Matter, B.;
Mays, C.; Mazouzi, I.; Mazowiecka, K.; Mazzucato, M. T.; McClure, R.;
McDaniel, B.; McGarry, P.; McKee, G. D.; McMillan, D.; Mellor, R.;
Mellors, P.; Merc, J.; Mercer, S.; Miller, K.; Mimeev, A.; Mitchell,
G.; Moe, J. L.; Mohr, G.; Molders, B. B.; Moldoveanu, R. M.; Moody,
E.; Mooney, C.; Moreno-Martinez, C.; Morford, C.; Morgan, A.; Morrill,
K.; Mottino, V.; Moyant, B.; Muehlisch, W.; Muller, E.; Myllymaki, T.;
Napier, S.; Naujok, J.; Neely, C.; Negus, M.; Nelson, D.; Nembrini,
S.; Nethercott, J.; Newgrosh, B.; Newman, C.; Nica, O.; Nicholson, J.;
Nissinen, M.; Nordnes, J.; Norris, A. G.; North, O.; Nuber, K.; Nuta,
M. -C.; O'Callaghan, G.; Oikkonen, A.; Olejarski, R.; Orsval, R.;
Ostler, J.; Ozga, K.; Paklin, N. N.; Pandey, A.; Pani, M.; Pantoni,
P.; Pearsall, E. R.; Pedersen, J. K.; Peixoto, J.; Pemberton, S.;
Perello, C.; Perlmutter, P. R. G.; Perozzi, E.; Perry, B.; Pettitt,
D.; Phillips, M.; Pidgley, K.; Piekarska, N.; Pierce, R.; Piroddu, F.;
Playle, T.; Plewinska, M.; Poffel, L.; Pogrebenko, S.; Pollard, T.;
Poole, C. W.; Post, A.; Preston, D. L. M.; Pulokas, T.; Purontakanen,
J.; Pusch, E.; Pyne, S.; Quinn, J.; Quiroga-Rodriguez, E.; Raab, H.;
Radford, C. A.; Rahimi, V. M.; Ravasi, C. E.; Regan, I.; Reisch,
F.; Renz, M.; Replogle, B.; Richmond, J.; Rike, E.; Ringsak, Q.;
Ringwald, F.; Rojas, A. E. M.; Ronsen, J. P.; Roovers, K.; Ros, J.;
Rossman, J.; Roubroeks, S. L.; Rounds, T.; Roynon, G.; Ruedinger,
C.; Ruh, M.; Rutledge, N.; Salinas, G. F.; Sanislav, O.; Sankala,
H.; Saracino, L.; Savels, M.; Sayle, J. A.; Schafer, T.; Scheuss,
U.; Schindler, M.; Schmalz, S.; Schmida, K.; Scholze, T.; Schulz, P.;
Schupper, L.; Scott, J.; Scott, M.; Sejpka, J.; Selig, G.; Shaw, B. M.;
Shearwater, G.; Sheldon, L.; Shelton, J.; Sheppard, A.; Shirvanian,
A.; Shockley, M.; Siddall, K. L.; Sijens, M. J.; Silva, P.; Simister,
D. J.; Simmons, M.; Skillman, D.; Slivka, R.; Smith, I. A.; Smith, M.;
Smith, R.; Snyder, J.; Sobczuk, B.; Somsikova, L. L.; Souders, M.;
Spanjaard, M.; Springer, A.; Stallone, T.; Stano, M.; Stelter, D.;
Stephan, R. W.; Stevens, R.; Stewart, P. D.; Stoca, A. D.; Stuart,
J.; Sue, J.; Summerlin, P. S.; Taylor, S. R.; Tepper, M.; Tertnes,
R.; Thebarge, J.; Thomaidis, P.; Thornton, J.; Tomic, D.; Tompkins,
J.; Tormanen, T.; Torsa, A.; Triltzsch, G.; Truog, D., II; Tukendorf,
D.; Turaev, T.; Uhl, I.; Unger, C.; van Boven, C.; Van Der Hilst,
R.; Van Grijfland, P.; Veillette, M.; Velthuis, R. H. B.; Verdelis,
P.; Verga, M.; Verhoeven, G.; Vertinskis, A.; Vigil, P.; Volkel, D.;
Vorley, T.; Vorobjov, T.; Vorochilov, V.; Wah, L. L. W.; Walravens,
E.; Ward, D.; Ward, S.; Warner, J. D.; Wartenberg, J.; Washbourn,
G.; Waterfield, P.; Wegert, S.; Wegner-Kaminski, A.; Weilant, D.;
Westbrook, D.; Wheat, J.; Wheeldon, N.; Whitfield, D.; Wille, A.;
Winkle, M. V.; Wollenhaupt, G.; Woodhams, D.; Wrobel, A.; Yandle,
C.; Zeddam, J.; Zeigler, D. R.; Zinke, L.; Zinn, B.; Zormpa, I.; Mas,
J. G.; Williams, G. V.
2012MPEC....F..109F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: VizieR Online Data Catalog: The Magellanic Mopra Assessment
(MAGMA). I. (Wong+, 2011)
Authors: Wong, T.; Hughes, A.; Ott, J.; Muller, E.; Pineda, J. L.;
Bernard, J. -P.; Chu, Y. -H.; Fukui, Y.; Gruendl, R. A.; Henkel, C.;
Kawamura, A.; Klein, U.; Looney, L. W.; Maddison, S.; Mizuno, Y.;
Paradis, D.; Seale, J.; Daniel, E. W.
2012yCat..21970016W Altcode:
Observations were performed with the Australia Telescope National
Facility (ATNF) Mopra 22m telescope from 2005 May to 2010 October. <P
/>(3 data files).
---------------------------------------------------------
Title: Parametrized 3D models of neutrino-driven supernova
explosions. Neutrino emission asymmetries and gravitational-wave
signals
Authors: Müller, E.; Janka, H. -Th.; Wongwathanarat, A.
2012A&A...537A..63M Altcode: 2011arXiv1106.6301M
Time-dependent and direction-dependent neutrino and gravitational-wave
(GW) signatures are presented for a set of three-dimensional (3D)
hydrodynamic models of parametrized, neutrino-driven supernova
explosions of non-rotating 15 and 20 M<SUB>⊙</SUB> stars. We
employed an approximate treatment of neutrino transport based on a gray
spectral description and a ray-by-ray treatment of multi-dimensional
effects. Owing to the excision of the high-density core of the
proto-neutron star (PNS) and the use of an axis-free (Yin-Yang) overset
grid, the models can be followed from the post-bounce accretion phase
through the onset of the explosion into more than one second of the
early cooling evolution of the PNS without imposing any symmetry
restrictions and covering a full sphere. Gravitational waves and
neutrino emission exhibit the generic time-dependent features already
known from 2D (axi-symmetric) models. Violent non-radial hydrodynamic
mass motions in the accretion layer and their interaction with the outer
layers of the proto-neutron star together with anisotropic neutrino
emission give rise to a GW signal with an amplitude of ~5-20 cm in
the frequency range of 100-500 Hz. The GW emission from mass motions
usually reaches a maximum before the explosion sets in. After the onset
of the explosion the GW signal exhibits a low-frequency modulation,
in some cases describing a quasi-monotonic growth, associated with
the non-spherical expansion of the explosion shock wave and the
large-scale anisotropy of the escaping neutrino flow. Variations of the
mass-quadrupole moment caused by convective activity inside the nascent
neutron star add a high-frequency component to the GW signal during the
post-explosion phase. The GW signals exhibit strong variability between
the two polarizations, different explosion simulations and different
observer directions, and besides common basic features do not possess
any template character. The neutrino emission properties (fluxes and
effective spectral temperatures) show fluctuations over the neutron star
surface on spatial and temporal scales that reflect the different types
of non-spherical mass motions in the supernova core, i.e., post-shock
overturn flows and proto-neutron star convection. However, because
very prominent, quasi-periodic sloshing motions of the shock caused by
the standing accretion-shock instability are absent and the emission
from different surface areas facing an observer adds up incoherently,
the modulation amplitudes of the measurable neutrino luminosities and
mean energies are significantly lower than predicted by 2D simulations.
---------------------------------------------------------
Title: A New Stellar Mixing Process Operating below Shell Convection
Zones Following Off-center Ignition
Authors: Mocák, M.; Meakin, Casey A.; Müller, E.; Siess, L.
2011ApJ...743...55M Altcode: 2011arXiv1108.4433M
During most stages of stellar evolution the nuclear burning of lighter
to heavier elements results in a radial composition profile which
is stabilizing against buoyant acceleration, with light material
residing above heavier material. However, under some circumstances,
such as off-center ignition, the composition profile resulting from
nuclear burning can be destabilizing and characterized by an outwardly
increasing mean molecular weight. The potential for instabilities under
these circumstances and the consequences that they may have on stellar
structural evolution remain largely unexplored. In this paper we study
the development and evolution of instabilities associated with unstable
composition gradients in regions that are initially stable according
to linear Schwarzschild and Ledoux criteria. In particular, we study
the development of turbulent flow under a variety of stellar evolution
conditions with multi-dimensional hydrodynamic simulation; the phases
studied include the core helium flash in a 1.25 M <SUB>⊙</SUB>
star, the core carbon flash in a 9.3 M <SUB>⊙</SUB> star, and
oxygen shell burning in a 23 M <SUB>⊙</SUB> star. The results of
our simulations reveal a mixing process associated with regions having
outwardly increasing mean molecular weight that reside below convection
zones. The mixing is not due to overshooting from the convection
zone, nor is it due directly to thermohaline mixing which operates
on a timescale several orders of magnitude larger than the simulated
flows. Instead, the mixing appears to be due to the presence of a wave
field induced in the stable layers residing beneath the convection
zone which enhances the mixing rate by many orders of magnitude and
allows a thermohaline type mixing process to operate on a dynamical,
rather than thermal, timescale. The mixing manifests itself in the form
of overdense and cold blob-like structures originating from density
fluctuations at the lower boundary of convective shell and "shooting"
down into the core. They are enriched with nuclearly processed material,
hence leaving behind traces of higher mean molecular weight. In these
regions, we find that initially smooth composition gradients steepen
into stair-step-like profiles in which homogeneous, mixed regions are
separated by composition jumps. These step-like profiles are then seen
to evolve by a process of interface migration driven by turbulent
entrainment. We discuss our results in terms of related laboratory
phenomena and associated theoretical developments. We also discuss
the degree to which the simulated mixing rates depend on the numerical
resolution, and what future steps can be taken to capture the mixing
rates accurately.
---------------------------------------------------------
Title: Surveying the Agents of Galaxy Evolution in the
Tidally Stripped, Low Metallicity Small Magellanic Cloud
(SAGE-SMC). I. Overview
Authors: Gordon, K. D.; Meixner, M.; Meade, M. R.; Whitney, B.;
Engelbracht, C.; Bot, C.; Boyer, M. L.; Lawton, B.; Sewiło, M.;
Babler, B.; Bernard, J. -P.; Bracker, S.; Block, M.; Blum, R.; Bolatto,
A.; Bonanos, A.; Harris, J.; Hora, J. L.; Indebetouw, R.; Misselt,
K.; Reach, W.; Shiao, B.; Tielens, X.; Carlson, L.; Churchwell, E.;
Clayton, G. C.; Chen, C. -H. R.; Cohen, M.; Fukui, Y.; Gorjian, V.;
Hony, S.; Israel, F. P.; Kawamura, A.; Kemper, F.; Leroy, A.; Li,
A.; Madden, S.; Marble, A. R.; McDonald, I.; Mizuno, A.; Mizuno, N.;
Muller, E.; Oliveira, J. M.; Olsen, K.; Onishi, T.; Paladini, R.;
Paradis, D.; Points, S.; Robitaille, T.; Rubin, D.; Sandstrom, K.;
Sato, S.; Shibai, H.; Simon, J. D.; Smith, L. J.; Srinivasan, S.;
Vijh, U.; Van Dyk, S.; van Loon, J. Th.; Zaritsky, D.
2011AJ....142..102G Altcode: 2011arXiv1107.4313G
The Small Magellanic Cloud (SMC) provides a unique laboratory for
the study of the lifecycle of dust given its low metallicity (~1/5
solar) and relative proximity (~60 kpc). This motivated the SAGE-SMC
(Surveying the Agents of Galaxy Evolution in the Tidally Stripped,
Low Metallicity Small Magellanic Cloud) Spitzer Legacy program with
the specific goals of studying the amount and type of dust in the
present interstellar medium, the sources of dust in the winds of
evolved stars, and how much dust is consumed in star formation. This
program mapped the full SMC (30 deg<SUP>2</SUP>) including the body,
wing, and tail in seven bands from 3.6 to 160 μm using IRAC and MIPS
on the Spitzer Space Telescope. The data were reduced and mosaicked,
and the point sources were measured using customized routines specific
for large surveys. We have made the resulting mosaics and point-source
catalogs available to the community. The infrared colors of the SMC
are compared to those of other nearby galaxies and the 8 μm/24 μm
ratio is somewhat lower than the average and the 70 μm/160 μm ratio
is somewhat higher than the average. The global infrared spectral
energy distribution (SED) shows that the SMC has approximately 1/3
the aromatic emission/polycyclic aromatic hydrocarbon abundance of
most nearby galaxies. Infrared color-magnitude diagrams are given
illustrating the distribution of different asymptotic giant branch
stars and the locations of young stellar objects. Finally, the average
SED of H II/star formation regions is compared to the equivalent
Large Magellanic Cloud average H II/star formation region SED. These
preliminary results will be expanded in detail in subsequent papers.
---------------------------------------------------------
Title: Multidimensional hydrodynamic simulations of the hydrogen
injection flash
Authors: Mocák, M.; Siess, L.; Müller, E.
2011A&A...533A..53M Altcode: 2011arXiv1106.3260M
Context. The injection of hydrogen into the convection shell powered
by helium burning during the core helium flash is commonly encountered
during the evolution of metal-free and extremely metal-poor low-mass
stars. Multidimensional hydrodynamic simulations indicate that
the hydrogen injection may also occur in more metal-rich stars due
to turbulent entrainment that accelerates the growth of the shell
convection zone and increases its size. However, one-dimensional stellar
models cast doubts that helium-flash hydrogen mixing does occur as it
requires the crossing of an entropy barrier at the helium-hydrogen
interface. <BR /> Aims: With specifically designed multidimensional
hydrodynamic simulations, we aim to prove that an entropy barrier is no
obstacle to the growth of the helium-burning shell convection zone in
the helium core of a metal-rich Population I star, i.e. convection can
penetrate into the hydrogen-rich layers for these stars, too. We study
whether this is also possible in one-dimensional stellar evolutionary
calculations. <BR /> Methods: We artificially shift the hydrogen-rich
layer closer to the outer edge of the helium-burning shell convection
zone in a Population I star with a mass of 1.25 M<SUB>⊙</SUB>,
and simulate the subsequent evolution in two and three dimensions,
respectively. We also perform stellar evolutionary calculations of
the core helium flash in metal-rich stars implementing turbulent
entrainment by means of a simple prescription. These simulations
were performed with the Eulerian hydrodynamical code HERAKLES and
the stellar evolution code STAREVOL, respectively. <BR /> Results: Our
hydrodynamical simulations show that the helium-burning shell convection
zone in the helium core moves across the entropy barrier and reaches
the hydrogen-rich layers. This leads to a mixing of protons into the
hotter layers of the core and to a rapid increase in the nuclear energy
production at the upper edge of the helium-burning convection shell -
the hydrogen injection flash. As a result, a second convection zone
appears in the hydrogen-rich layers. In contrast to one-dimensional
models, the entropy barrier separating the two convective shells from
each other is largely permeable to chemical transport when allowing
for multidimensional flow and consequently hydrogen is continuously
mixed deep into the helium core. We find it difficult to replicate
this behavior using one-dimensional stellar evolutionary calculations.
---------------------------------------------------------
Title: Influence of thermonuclear effects on the collapse of
supermassive stars
Authors: Montero, Pedro J.; Janka, H. -T.; Müller, E.; Müller, B.
2011JPhCS.314a2077M Altcode:
We present results of general relativistic simulations of collapsing
supermassive stars using the two-dimensional general relativistic
numerical code Nada, which solves the Einstein equations written in the
BSSN formalism and the general relativistic hydrodynamic equations with
high resolution shock capturing schemes. These numerical simulations
use a tabulated equation of state which includes effects of radiation
and gas pressure, and those associated with the electron-positron
pairs. We also take into account the effect of thermonuclear energy
released by hydrogen and helium burning. We find that objects with mass
≈ 5 × 10<SUP>5</SUP>M<SUB></SUB> and initial metallicity greater
than Z<SUB>CNO</SUB> ≈ 0.004 do explode if non-rotating, while the
threshold metallicity for an explosion is reduced to Z<SUB>CNO</SUB>
≈ 0.002 for objects uniformly rotating.
---------------------------------------------------------
Title: Hydromagnetic instabilities and magnetic field amplification
in core collapse supernovae
Authors: Cerdá-Durán, P.; Obergaulinger, M.; Aloy, M. A.; Font,
J. A.; Müller, E.
2011JPhCS.314a2079C Altcode:
Some of the most violent events in the universe, the gamma ray burst,
could be related to the gravitational collapse of massive stellar
cores. The recent association of long GRBs to some class of type Ic
supernova seems to support this view. In such scenario fast rotation,
strong magnetic fields and general relativistic effects are key
ingredients. It is thus important to understand the mechanism that
amplifies the magnetic field under that conditions. I present global
simulations of the magneto-rotational collapse of stellar cores
in general relativity and semi-global simulations of hydromagnetic
instabilities under core collapse conditions. I discuss effect of the
magneto-rotational instability and the magnetic field amplification
during the collapse, the uncertainties in this process and the dynamical
effects in the supernova explosion.
---------------------------------------------------------
Title: High-order methods for the simulation of hydromagnetic
instabilities in core-collapse supernovae
Authors: Rembiasz, T.; Obergaulinger, M.; Aloy, M. Angel;
Cerdá-Durán, P.; Müller, E.
2011IAUS..274..479R Altcode:
We present an assessment of the accuracy of a recently developed MHD
code used to study hydromagnetic flows in supernovae and related
events. The code, based on the constrained transport formulation,
incorporates unprecedented ultra-high-order methods (up to 9th order)
for the reconstruction and the most accurate approximate Riemann
solvers. We estimate the numerical resistivity of these schemes in
tearing instability simulations.
---------------------------------------------------------
Title: The CO Isotope Ratio of the Large Magellanic Cloud
Authors: Wyss, Sarah; Ott, J.; Meier, D.; Wong, T.; Hughes, A.;
Pineda, J.; Muller, E.
2011AAS...21725126W Altcode: 2011BAAS...4325126W
Giant molecular clouds (GMCs) are the home of star formation, yet are
difficult to observe and thus their physical characteristics remain
largely unknown. The proximity, size, inclination and star-forming
properties of the Large Magellanic Cloud (LMC, distance 50kpc) present
a perfect opportunity for a comprehensive, high-spectral-resolution
and high-spatial-resolution survey of these clouds. Using the
<SUP>12</SUP>CO (1-0) and <SUP>13</SUP>CO (1-0) Magellanic Mopra
Assessment (MAGMA) data, we study over 155 giant molecular clouds
distributed throughout the LMC at 8pc resolution. The <SUP>13</SUP>CO
(1-0) transition is detected at or above the level of significance
in all clouds examined. The intensity ratio of the <SUP>13</SUP>CO
(1-0) to <SUP>12</SUP>CO (1-0) transitions is found to be highly
uniform across the LMC, not varying strongly with GMC evolutionary
state, galactocentric regions, star formation rate or interaction
with the Milky Way. We discover an unexplained correlation between
<SUP>12</SUP>CO average brightness temperature and the isotope intensity
ratio. We produce galaxy-wide spectra in <SUP>12</SUP>CO (1-0) and
<SUP>13</SUP>CO (1-0) and examine the galaxy-wide <SUP>13</SUP>CO (1-0)
to <SUP>12</SUP>CO (1-0) ratio, simulating observations of similar,
more distant galaxies. Comparison of this ratio with the ratio measured
locally from individual clouds yields an overall <SUP>13</SUP>CO (1-0)
filling factor of 0.3 of <SUP>12</SUP>CO(1-0).
---------------------------------------------------------
Title: Spitzer View of Massive Star Formation at Reduced Metallicity
Environment
Authors: Chen, C. H. Rosie; Indebetouw, R.; Chu, Y.; Gruendl, R.;
Muller, E.; Fukui, Y.; Kawamura, A.; Testor, G.; Gordon, K.; Heitsch,
F.; Leroy, A.; Meixner, M.; Seale, J.; Sewilo, M.; Sloan, G.; Whitney,
B.; SAGE Team
2011AAS...21725828C Altcode: 2011BAAS...4325828C
Recent Spitzer mid-IR observations have revealed a large number of
individually resolved massive young stellar objects (YSOs) in the
Magellanic clouds, providing an excellent opportunity to study massive
star formation with metallicity and galactic environment different
from the Milky Way. Using Spitzer IRAC/MIPS data from SAGE survey and
complementary high-resolution ground-based optical/near-IR data, we
have identified YSOs in HII complexes in the Large and Small Magellanic
Cloud (LMC and SMC) and a large area in the Magellanic Bridge. These
systems span a metallicity range of 1/3-1/8 Zo, and different galactic
environments with star formation modes from mainly self-propagating in
the LMC to tidally disrupted in the Bridge. We have modeled spectral
energy distributions of the YSOs and found that they have masses
ranging from 4 to 45 Mo in the LMC and SMC, while the most massive ones
in the Bridge are < 10 Mo. YSOs in these three systems are found
to span a wide range of evolutionary stages from highly embedded to
surrounded by remnant material, though for the same mass range YSOs
in the Bridge appear less embedded as almost all of them are visible
at optical, opposed to only a small fraction in the LMC. The smaller
extinction may be due to Bridge's lower dust content in either the
CO clouds or circumstellar envelopes, or both. Using surveys in Hα,
CO, and HI of these three systems, we further investigate the causal
relationship between gas and stars. Examination of individual regions
shows that massive YSOs tend to be found near ionized gas, i.e., where
massive stars formed a few Myr ago, and the correlation is strongest
for O-type YSOs. It appears that energy feedback plays a significant
role in massive star formation. Star formation efficiencies in regions
in these three systems are comparable, < 1/100-1/1000.
---------------------------------------------------------
Title: The core helium flash revisited. III. From Population I to
Population III stars
Authors: Mocák, M.; Campbell, S. W.; Müller, E.; Kifonidis, K.
2010A&A...520A.114M Altcode: 2010arXiv1003.3646M
Context. Degenerate ignition of helium in low-mass stars at the end of
the red giant branch phase leads to dynamic convection in their helium
cores. One-dimensional (1D) stellar modeling of this intrinsically
multi-dimensional dynamic event is likely to be inadequate. Previous
hydrodynamic simulations imply that the single convection zone in
the helium core of metal-rich Pop I stars grows during the flash on a
dynamic timescale. This may lead to hydrogen injection into the core and
to a double convection zone structure as known from one-dimensional
core helium flash simulations of low-mass Pop III stars. <BR />
Aims: We perform hydrodynamic simulations of the core helium flash
in two and three dimensions to better constrain the nature of these
events. To this end we study the hydrodynamics of convection within
the helium cores of a 1.25 M_⊙ metal-rich Pop I star (Z = 0.02),
and, for the first time, a 0.85 M_⊙ metal-free Pop III star (Z = 0)
near the peak of the flash. These models possess single and double
convection zones, respectively. <BR /> Methods: We use 1D stellar
models of the core helium flash computed with state-of-the-art stellar
evolution codes as initial models for our multidimensional hydrodynamic
study, and simulate the evolution of these models with the Riemann
solver based hydrodynamics code Herakles, which integrates the Euler
equations coupled with source terms corresponding to gravity and nuclear
burning. <BR /> Results: The hydrodynamic simulation of the Pop I model
involving a single convection zone covers 27 h of stellar evolution,
while the hydrodynamic simulations of a double convection zone, in
the Pop III model, span 1.8 h of stellar life. We find differences
between the predictions of mixing length theory and our hydrodynamic
simulations. The simulation of the single convection zone in the Pop I
model shows a strong growth of the size of the convection zone due to
turbulent entrainment. We therefore predict that for the Pop I model
a hydrogen injection phase (i.e., hydrogen injection into the helium
core) will commence after about 23 days, which should eventually lead
to a double convection zone structure known from 1D stellar modeling
of low-mass Pop III stars. Our two and three-dimensional hydrodynamic
simulations of the double (Pop III) convection zone model show that the
velocity field in the convection zones is different from that given
by stellar evolutionary calculations. The simulations suggest that
the double convection zone decays quickly, the flow eventually being
dominated by internal gravity waves. The decay could be an artefact
caused by the mapping of the initial stellar model to the numerical
grid of our hydrodynamics code.
---------------------------------------------------------
Title: Simulations of the Magneto-rotational Instability in
Core-Collapse Supernovae
Authors: Obergaulinger, M.; Cerdá-Durán, P.; Müller, E.; Aloy, M. A.
2010ASPC..429..136O Altcode: 2009arXiv0911.3222O
We assess the importance of the magneto-rotational instability in
core-collapse supernovae by an analysis of the growth rates of unstable
modes in typical post-collapse systems and by numerical simulations of
simplified models. The interplay of differential rotation and thermal
stratification defines different instability regimes which we confirm
in our simulations. We investigate the termination of the growth of the
MRI by parasitic instabilities, establish scaling laws characterising
the termination amplitude, and study the long-term evolution of the
saturated turbulent state.
---------------------------------------------------------
Title: Physical properties of giant molecular clouds in the Large
Magellanic Cloud
Authors: Hughes, A.; Wong, T.; Ott, J.; Muller, E.; Pineda, J. L.;
Mizuno, Y.; Bernard, J. -P.; Paradis, D.; Maddison, S.; Reach, W. T.;
Staveley-Smith, L.; Kawamura, A.; Meixner, M.; Kim, S.; Onishi, T.;
Mizuno, N.; Fukui, Y.
2010MNRAS.406.2065H Altcode: 2010arXiv1004.2094H; 2010MNRAS.tmp..873H
The Magellanic Mopra Assessment (MAGMA) is a high angular resolution
<SUP>12</SUP>CO (J = 1 -> 0) mapping survey of giant molecular
clouds (GMCs) in the Large Magellanic Cloud (LMC) and Small Magellanic
Cloud using the Mopra Telescope. Here we report on the basic physical
properties of 125 GMCs in the LMC that have been surveyed to date. The
observed clouds exhibit scaling relations that are similar to those
determined for Galactic GMCs, although LMC clouds have narrower
linewidths and lower CO luminosities than Galactic clouds of a
similar size. The average mass surface density of the LMC clouds is 50
M<SUB>solar</SUB>pc<SUP>-2</SUP>, approximately half that of GMCs in
the inner Milky Way. We compare the properties of GMCs with and without
signs of massive star formation, finding that non-star-forming GMCs
have lower peak CO brightness than star-forming GMCs. We compare the
properties of GMCs with estimates for local interstellar conditions:
specifically, we investigate the HI column density, radiation field,
stellar mass surface density and the external pressure. Very few
cloud properties demonstrate a clear dependence on the environment;
the exceptions are significant positive correlations between (i) the
HI column density and the GMC velocity dispersion, (ii) the stellar
mass surface density and the average peak CO brightness and (iii)
the stellar mass surface density and the CO surface brightness. The
molecular mass surface density of GMCs without signs of massive star
formation shows no dependence on the local radiation field, which
is inconsistent with the photoionization-regulated star formation
theory proposed by McKee. We find some evidence that the mass surface
density of the MAGMA clouds increases with the interstellar pressure,
as proposed by Elmegreen, but the detailed predictions of this model
are not fulfilled once estimates for the local radiation field,
metallicity and GMC envelope mass are taken into account.
---------------------------------------------------------
Title: The Arecibo L-band Feed Array Zone of Avoidance
Survey. I. Precursor Observations Through the Inner and Outer Galaxy
Authors: Henning, P. A.; Springob, C. M.; Minchin, R. F.; Momjian,
E.; Catinella, B.; McIntyre, T.; Day, F.; Muller, E.; Koribalski,
B.; Rosenberg, J. L.; Schneider, S.; Staveley-Smith, L.; van Driel, W.
2010AJ....139.2130H Altcode: 2010arXiv1002.2933H
The Arecibo L-band Feed Array (ALFA) is being used to conduct a
low-Galactic latitude survey, to map the distribution of galaxies
and large-scale structures behind the Milky Way through detection of
galaxies' neutral hydrogen (H I) 21 cm emission. This Zone of Avoidance
(ZOA) survey finds new H I galaxies which lie hidden behind the Milky
Way, and also provides redshifts for partially obscured galaxies
known at other wavelengths. Before the commencement of the full
survey, two low-latitude precursor regions were observed, totaling
138 deg<SUP>2</SUP>, with 72 H I galaxies detected. Detections through
the inner Galaxy generally have no cataloged counterparts in any other
waveband, due to the heavy extinction and stellar confusion. Detections
through the outer Galaxy are more likely to have Two Micron All
Sky Survey counterparts. We present the results of these precursor
observations, including a catalog of the detected galaxies, with their
H I parameters. The survey sensitivity is well described by a flux-
and linewidth-dependent signal-to-noise ratio of 6.5. ALFA ZOA galaxies,
which also have H I measurements in the literature, show good agreement
between our measurements and previous work. The inner Galaxy precursor
region was chosen to overlap the H I Parkes Zone of Avoidance Survey, so
ALFA performance could be quickly assessed. The outer Galaxy precursor
region lies north of the Parkes sky. Low-latitude large-scale structure
in this region is revealed, including an overdensity of galaxies near
ell = 183° and between 5000-6000 km s<SUP>-1</SUP> in the ZOA. The
full ALFA ZOA survey will be conducted in two phases: a shallow survey
using the observing techniques of the precursor observations, and
also a deep phase with much longer integration time, with thousands
of galaxies predicted for the final catalog.
---------------------------------------------------------
Title: Local simulations of the magnetized Kelvin-Helmholtz
instability in neutron-star mergers
Authors: Obergaulinger, M.; Aloy, M. A.; Müller, E.
2010A&A...515A..30O Altcode: 2010arXiv1003.6031O
Context. Global magnetohydrodynamic simulations show the growth of
Kelvin-Helmholtz instabilities at the contact surface of two merging
neutron stars. That region has been identified as the site of efficient
amplification of magnetic fields. However, these global simulations,
due to numerical limitations, were unable to determine the saturation
level of the field strength, and thus the possible back-reaction of
the magnetic field onto the flow. <BR /> Aims: We investigate the
amplification of initially weak magnetic fields in Kelvin-Helmholtz
unstable shear flows, and the back-reaction of the field onto the
flow. <BR /> Methods: We use a high-resolution finite-volume ideal MHD
code to perform 2D and 3D local simulations of hydromagnetic shear
flows, both for idealized systems and simplified models of merger
flows. <BR /> Results: In 2D, the magnetic field is amplified on time
scales of less than 0.01 ms until it reaches locally equipartition
with the kinetic energy. Subsequently, it saturates due to resistive
instabilities that disrupt the Kelvin-Helmholtz unstable vortex and
decelerate the shear flow on a secular time scale. We determine scaling
laws of the field amplification with the initial field strength and
the grid resolution. In 3D, the hydromagnetic mechanism seen in 2D
may be dominated by purely hydrodynamic instabilities leading to less
filed amplification. We find maximum magnetic fields ~10<SUP>16</SUP>
G locally, and rms maxima within the box ~10<SUP>15</SUP> G. However,
due to the fast decay of the shear flow such strong fields exist only
for a short period (<0.1 ms). In the saturated state of most models,
the magnetic field is mainly oriented parallel to the shear flow for
rather strong initial fields, while weaker initial fields tend to
lead to a more balanced distribution of the field energy among the
components. In all models the flow shows small-scale features. The
magnetic field is at most in energetic equipartition with the decaying
shear flow. <BR /> Conclusions: The magnetic field may be amplified
efficiently to very high field strengths, the maximum field energy
reaching values of the order of the kinetic energy associated with
the velocity components transverse to the interface between the two
neutron stars. However, the dynamic impact of the field onto the flow
is limited to the shear layer, and it may not be adequate to produce
outflows, because the time during which the magnetic field stays close
to its maximum value is short compared to the time scale for launching
an outflow (i.e., a few milliseconds).
---------------------------------------------------------
Title: An axis-free overset grid in spherical polar coordinates for
simulating 3D self-gravitating flows
Authors: Wongwathanarat, A.; Hammer, N. J.; Müller, E.
2010A&A...514A..48W Altcode: 2010arXiv1003.1633W
<BR /> Aims: Three dimensional explicit hydrodynamic codes based on
spherical polar coordinates using a single spherical polar grid suffer
from a severe restriction of the time step size due to the convergence
of grid lines near the poles of the coordinate system. More importantly,
numerical artifacts are encountered at the symmetry axis of the grid
where boundary conditions have to be imposed that flaw the flow near
the axis. The first problem can be eased and the second one avoided
by applying an overlapping grid technique. <BR /> Methods: A type of
overlapping grid in spherical coordinates is adopted. This so called
“Yin-Yang” grid is a two-patch overset grid proposed by Kageyama
and Sato for geophysical simulations. Its two grid patches contain
only the low-latitude regions of the usual spherical polar grid and are
combined together in a simple manner. This property of the Yin-Yang grid
greatly simplifies its implementation into a 3D code already employing
spherical polar coordinates. It further allows for a much larger time
step in 3D simulations using high angular resolution (⪉1°) than that
required in 3D simulations using a regular spherical grid with the same
angular resolution. <BR /> Results: The Yin-Yang grid is successfully
implemented into a 3D version of the explicit Eulerian grid-based code
PROMETHEUS including self-gravity. The modified code successfully
passed several standard hydrodynamic tests producing results which
are in very good agreement with analytic solutions. Moreover, the
solutions obtained with the Yin-Yang grid exhibit no peculiar behaviour
at the boundary between the two grid patches. The code has also been
successfully used to model astrophysically relevant situations, namely
equilibrium polytropes, a Taylor-Sedov explosion, and Rayleigh-Taylor
instabilities. According to our results, the usage of the Yin-Yang grid
greatly enhances the suitability and efficiency of 3D explicit Eulerian
codes based on spherical polar coordinates for astrophysical flows.
---------------------------------------------------------
Title: Three-dimensional Simulations of Mixing Instabilities in
Supernova Explosions
Authors: Hammer, N. J.; Janka, H. -Th.; Müller, E.
2010ApJ...714.1371H Altcode: 2009arXiv0908.3474H
We present the first three-dimensional (3D) simulations of the
large-scale mixing that takes place in the shock-heated stellar layers
ejected in the explosion of a 15.5 M <SUB>sun</SUB> blue supergiant
star. The blast is initiated and powered by neutrino-energy deposition
behind the stalled shock by means of choosing sufficiently high
neutrino luminosities from the contracting, nascent neutron star,
whose high-density core is excised and replaced by a retreating
inner grid boundary. The outgoing supernova shock is followed beyond
its breakout from the stellar surface more than 2 hr after the core
collapse. Violent convective overturn in the post-shock layer causes
the explosion to start with significant large-scale asphericity, which
acts as a trigger of the growth of Rayleigh-Taylor instabilities at the
composition interfaces of the exploding star. Despite the absence of a
strong Richtmyer-Meshkov instability at the H/He interface, which only a
largely deformed shock could instigate, deep inward mixing of hydrogen
is found as well as fast-moving, metal-rich clumps penetrating with
high velocities far into the hydrogen envelope of the star as observed,
for example, in the case of Supernova 1987A. Also individual clumps
containing a sizeable fraction of the ejected iron-group elements
(up to several 10<SUP>-3</SUP> M <SUB>sun</SUB>) are obtained in some
models. The metal core of the progenitor is partially turned over
with nickel-dominated fingers overtaking oxygen-rich bullets and both
nickel and oxygen moving well ahead of the material from the carbon
layer. Comparing with corresponding two-dimensional (axially symmetric;
2D) calculations, we determine the growth of the Rayleigh-Taylor
fingers to be faster, the deceleration of the dense metal-carrying
clumps in the helium and hydrogen layers to be reduced, the asymptotic
clump velocities in the hydrogen shell to be higher (up to ~4500 km
s<SUP>-1</SUP> for the considered progenitor and an explosion energy
of 10<SUP>51</SUP> erg, instead of lsim2000 km s<SUP>-1</SUP> in 2D),
and the outward radial mixing of heavy elements and inward mixing of
hydrogen to be more efficient in 3D than in 2D. We present a simple
argument that explains these results as a consequence of the different
action of drag forces on moving objects in the two geometries.
---------------------------------------------------------
Title: Characterizing the Low-Mass Molecular Component in the Northern
Small Magellanic Cloud
Authors: Muller, E.; Ott, J.; Hughes, A.; Pineda, J. L.; Wong, T.;
Mizuno, N.; Kawamura, A.; Mizuno, Y.; Fukui, Y.; Onishi, T.; Rubio, M.
2010ApJ...712.1248M Altcode: 2010arXiv1001.4757M
We present here the first results from a high-resolution survey of
the <SUP>12</SUP>CO(J = 1-0) emission across the northern part of
the poorly enriched Small Magellanic Cloud (SMC), made with the ATNF
Mopra telescope. Three molecular complexes detected in the lower
resolution NANTEN survey are mapped with a beam FWHM of ~42”, to
sensitivities of approximately 210 mK per 0.9 km s<SUP>-1</SUP> channel,
resolving each complex into 4-7 small clouds of masses in the range
of M <SUB>vir</SUB> ~ 10<SUP>3</SUP>-10<SUP>4</SUP> M <SUB>sun</SUB>
and with radii no larger than 16 pc. The northern SMC CO clouds follow
similar empirical relationships to the southern SMC population, yet
they appear relatively under-luminous for their size, suggesting that
the star-forming environment in the SMC is not homogeneous. Our data
also suggests that the CO cloud population has little or no extended
CO envelope on scales gsim30 pc, further evidence that the weak CO
component in the north SMC is being disassociated by penetrating
UV radiation. The new high-resolution data provide evidence for a
variable correlation of the CO integrated brightness with integrated
H I and 160 μm emission; in particular CO is often, but not always,
found coincident with peaks of 160 μm emission, verifying the need
for matching-resolution 160 μm and H I data for a complete assessment
of the SMC H<SUB>2</SUB> mass.
---------------------------------------------------------
Title: Molecular and Atomic Gas in the Large Magellanic
Cloud. II. Three-dimensional Correlation Between CO and H I
Authors: Fukui, Y.; Kawamura, A.; Wong, T.; Murai, M.; Iritani, H.;
Mizuno, N.; Mizuno, Y.; Onishi, T.; Hughes, A.; Ott, J.; Muller, E.;
Staveley-Smith, L.; Kim, S.
2009ApJ...705..144F Altcode: 2009arXiv0909.0382F
We compare the CO (J = 1-0) and H I emission in the Large Magellanic
Cloud in three dimensions, i.e., including a velocity axis in addition
to the two spatial axes, with the aim of elucidating the physical
connection between giant molecular clouds (GMCs) and their surrounding
H I gas. The CO J = 1-0 data set is from the second NANTEN CO survey
and the H I data set is from the merged Australia Telescope Compact
Array (ATCA) and Parkes Telescope surveys. The major findings of our
analysis are as follows: (1) GMCs are associated with an envelope
of H I emission, (2) in GMCs [average CO intensity] vprop [average
H I intensity]<SUP>1.1±0.1</SUP>, and (3) the H I intensity tends
to increase with the star formation activity within GMCs, from Type
I to Type III. An analysis of the H I envelopes associated with GMCs
shows that their average line width is 14 km s<SUP>-1</SUP> and the
mean density in the envelope is 10 cm<SUP>-3</SUP>. We argue that
the H I envelopes are gravitationally bound by GMCs. These findings
are consistent with a continual increase in the mass of GMCs via H I
accretion at an accretion rate of 0.05 M <SUB>sun</SUB> yr<SUP>-1</SUP>
over a timescale of 10 Myr. The growth of GMCs is terminated via
dissipative ionization and/or stellar-wind disruption in the final
stage of GMC evolution.
---------------------------------------------------------
Title: The core helium flash revisited. II. Two and three-dimensional
hydrodynamic simulations
Authors: Mocák, M.; Müller, E.; Weiss, A.; Kifonidis, K.
2009A&A...501..659M Altcode: 2008arXiv0811.4083M
Context: We study turbulent convection during the core helium flash
close to its peak by comparing the results of two and three-dimensional
hydrodynamic simulations. <BR />Aims: In a previous study we found
that the temporal evolution and the properties of the convection
inferred from two-dimensional hydrodynamic studies are similar
to those predicted by quasi-hydrostatic stellar evolutionary
calculations. However, as vorticity is conserved in axisymmetric
flows, two-dimensional simulations of convection are characterized by
incorrect dominant spatial scales and exaggerated velocities. Here, we
present three-dimensional simulations that eliminate the restrictions
and flaws of two-dimensional models and that provide a geometrically
unbiased insight into the hydrodynamics of the core helium flash. In
particular, we study whether the assumptions and predictions of
stellar evolutionary calculations based on the mixing-length theory
can be confirmed by hydrodynamic simulations. <BR />Methods: We used a
multidimensional Eulerian hydrodynamics code based on state-of-the-art
numerical techniques to simulate the evolution of the helium core of a
1.25 M<SUB>⊙</SUB> Pop I star. <BR />Results: Our three-dimensional
hydrodynamic simulations of the evolution of a star during the peak
of the core helium flash do not show any explosive behavior. The
convective flow patterns developing in the three-dimensional models are
structurally different from those of the corresponding two-dimensional
models, and the typical convective velocities are lower than those
found in their two-dimensional counterparts. Three-dimensional models
also tend to agree more closely with the predictions of mixing length
theory. Our hydrodynamic simulations show the turbulent entrainment that
leads to a growth of the convection zone on a dynamic time scale. In
contrast to mixing length theory, the outer part of the convection
zone is characterized by a subadiabatic temperature gradient.
---------------------------------------------------------
Title: Molecular and Atomic Gas in the Large Magellanic
Cloud. I. Conditions for CO Detection
Authors: Wong, T.; Hughes, A.; Fukui, Y.; Kawamura, A.; Mizuno, N.;
Ott, J.; Muller, E.; Pineda, J. L.; Welty, D. E.; Kim, S.; Mizuno,
Y.; Murai, M.; Onishi, T.
2009ApJ...696..370W Altcode: 2009arXiv0902.1578W
We analyze the conditions for detection of CO(1-0) emission in the
Large Magellanic Cloud, using the recently completed second NANTEN
CO survey. In particular, we investigate correlations between CO
integrated intensity and H I integrated intensity, peak brightness
temperature, and line width at a resolution of 2farcm6 (~40 pc). We
find that significant H I column density (exceeding ~10<SUP>21</SUP>
cm<SUP>-2</SUP>) and peak brightness temperature (exceeding ~20 K)
are necessary but not sufficient conditions for CO detection, with many
regions of strong H I emission not associated with molecular clouds. The
large scatter in CO intensities for a given H I intensity persists
even when averaging on scales of >200 pc, indicating that the
scatter is not solely due to local conversion of H I into H<SUB>2</SUB>
near GMCs. We focus on two possibilities to account for this scatter:
either there exist spatial variations in the I(CO) to N(H<SUB>2</SUB>)
conversion factor, or a significant fraction of the atomic gas is
not involved in molecular cloud formation. A weak tendency for CO
emission to be suppressed for large H I linewidths supports the second
hypothesis, insofar as large linewidths may be indicative of warm H I,
and calls into question the likelihood of forming molecular clouds
from colliding H I flows. We also find that the ratio of molecular
to atomic gas shows no significant correlation (or anticorrelation)
with the stellar surface density, though a correlation with midplane
hydrostatic pressure P<SUB>h</SUB> is found when the data are binned in
P<SUB>h</SUB> . The latter correlation largely reflects the increasing
likelihood of CO detection at high H I column density.
---------------------------------------------------------
Title: Molecular line mapping of the giant molecular cloud associated
with RCW 106 - III. Multimolecular line mapping
Authors: Lo, N.; Cunningham, M. R.; Jones, P. A.; Bains, I.; Burton,
M. G.; Wong, T.; Muller, E.; Kramer, C.; Ossenkopf, V.; Henkel, C.;
Deragopian, G.; Donnelly, S.; Ladd, E. F.
2009MNRAS.395.1021L Altcode: 2009arXiv0902.2452L; 2009MNRAS.tmp..403L
We present multimolecular line maps obtained with the Mopra telescope
towards the southern giant molecular cloud (GMC) complex G333,
associated with the H ii region RCW 106. We have characterized the GMC
by decomposing the 3D data cubes with gaussclumps, and investigated
spatial correlations among different molecules with principal component
analysis (PCA). We find no correlation between clump size and linewidth,
but a strong correlation between emission luminosity and linewidth. PCA
classifies molecules into high- and low-density tracers, and reveals
that HCO<SUP>+</SUP> and N<SUB>2</SUB>H<SUP>+</SUP> are anticorrelated.
---------------------------------------------------------
Title: Semi-global simulations of the magneto-rotational instability
in core collapse supernovae
Authors: Obergaulinger, M.; Cerdá-Durán, P.; Müller, E.; Aloy, M. A.
2009A&A...498..241O Altcode: 2008arXiv0811.1652O
Context: Possible effects of magnetic fields in core collapse supernovae
rely on an efficient amplification of the weak pre-collapse fields. It
has been suggested that the magneto-rotational instability (MRI) leads
to a rapid growth for these weak seed fields. Although plenty of MRI
studies exist for accretion disks, the application of their results to
core collapse supernovae is inhibited as the physics of supernova cores
is substantially different from that of accretion discs. <BR />Aims:
We address the problem of growth and saturation of the MRI in core
collapse supernovae by studying its evolution by means of semi-global
simulations, which combine elements of global and local simulations
by taking the presence of global background gradients into account
and using a local computational grid. We investigate, in particular,
the termination of the growth of the MRI and the properties of the
turbulence in the saturated state. <BR />Methods: We analyze the
dispersion relation of the MRI to identify different regimes of the
instability. This analysis is complemented by semi-global ideal MHD
simulations, where we consider core matter in a local computational box
(size ∼ 1 km) rotating at sub-Keplerian velocity and where we allow
for the presence of a radial entropy gradient, but neglect neutrino
radiation. <BR />Results: We identify six regimes of the MRI depending
on the ratio of the entropy and angular velocity gradient. Our numerical
models confirm the instability criteria and growth rates for all regimes
relevant to core-collapse supernovae. The MRI grows exponentially on
time scales of milliseconds, the flow and magnetic field geometries
being dominated by channel flows. We find MHD turbulence and efficient
transport of angular momentum. The MRI growth ceases once the channels
are disrupted by resistive instabilities (stemming from to the finite
conductivity of the numerical code), and MHD turbulence sets in. From an
analysis of the growth rates of the resistive instabilities, we deduce
scaling laws for the termination amplitude of the MRI, which agree
well with our numerical models. We determine the dependence of the
development of large-scale coherent flow structures in the saturated
state on the aspect ratio of the simulation boxes. <BR />Conclusions:
The MRI can grow rapidly under the conditions considered here, i.e.,
a rapidly rotating core in hydrostatic equilibrium, possibly endowed
with a nonvanishing entropy gradient, leading to fields exceeding
10<SUP>15</SUP>~G. More investigations are required to cover the
parameter space more comprehensively and to include more physical
effects.
---------------------------------------------------------
Title: Relativistic Simulations of Magneto-rotational Core Collapse
Authors: Font, J. A.; Cerdá-Durán, P.; Müller, E.; Antón, L.
2009ASPC..406...86F Altcode:
We introduce and discuss the basic features of a new numerical
code designed to handle ideal MHD flows in dynamical spacetimes
in general relativity, and particularly designed to investigate the
gravitational collapse of the core of massive stars leading to neutron
stars or black holes. After introducing the mathematical framework
for the general relativistic MHD equations and the Einstein equations
(within the so-called conformal flat condition) we present results
from two representative simulations of magneto-rotational stellar core
collapse. Our simulations highlight the importance of genuine magnetic
effects such as the magneto-rotational instability on the dynamics of
the process.
---------------------------------------------------------
Title: Early results from the SAGE-SMC Spitzer legacy
Authors: Gordon, Karl D.; Meixner, M.; Blum, R. D.; Reach, W.; Whitney,
B. A.; Harris, J.; Indebetouw, R.; Bolatto, A. D.; Bernard, J. -P.;
Sewilo, M.; Babler, B. L.; Block, M.; Bot, C.; Bracker, S.; Carlson,
L.; Churchwell, E.; Clayton, G. C.; Cohen, M.; Engelbracht, C. W.;
Fukui, Y.; Gorjian, V.; Hony, S.; Hora, J. L.; Israel, F.; Kawamura,
A.; Leroy, A. K.; Li, A.; Madden, S.; Marble, A. R.; Markwick-Kemper,
F.; Meade, M.; Misselt, K. A.; Mizuno, A.; Mizuno, N.; Muller, E.;
Oliveira, J. M.; Olsen, K.; Onishi, T.; Paladini, R.; Paradis, D.;
Points, S.; Robitaille, T.; Rubin, D.; Sandstrom, K. M.; Sato, S.;
Shibai, H.; Simon, J. D.; Smith, L. J.; Srinivasan, S.; Tielens,
A. G. G. M.; Vijh, U. P.; van Dyk, S.; van Loon, J. Th.; Volk, K.;
Zaritsky, D.
2009IAUS..256..184G Altcode:
Early results from the SAGE-SMC (Surveying the Agents of Galaxy
Evolution in the tidally-disrupted, low-metallicity Small Magellanic
Cloud) Spitzer legacy program are presented. These early results
concentrate on the SAGE-SMC MIPS observations of the SMC Tail
region. This region is the high H i column density portion of the
Magellanic Bridge adjacent to the SMC Wing. We detect infrared dust
emission and measure the gas-to-dust ratio in the SMC Tail and find
it similar to that of the SMC Body. In addition, we find two embedded
cluster regions that are resolved into multiple sources at all MIPS
wavelengths.
---------------------------------------------------------
Title: Equation-of-state dependent features in shock-oscillation
modulated neutrino and gravitational-wave signals from supernovae
Authors: Marek, A.; Janka, H. -T.; Müller, E.
2009A&A...496..475M Altcode: 2008arXiv0808.4136M
We present two-dimensional (axisymmetric) neutrino-hydrodynamic
simulations of the long-time accretion phase of a 15 M_⊙ progenitor
star after core bounce and before the launch of a supernova explosion,
when non-radial hydrodynamic instabilities like convection occur
in different regions of the collapsing stellar core and the standing
accretion shock instability (SASI) leads to large-amplitude oscillations
of the stalled shock with a period of tens of milliseconds. Our
simulations were performed with the Prometheus-Vertex code, which
includes a multi-flavor, energy-dependent neutrino transport scheme and
employs an effective relativistic gravitational potential. Testing the
influence of a stiff and a soft equation of state for hot neutron star
matter, we find that the non-radial mass motions in the supernova core
impose a time variability on the neutrino and gravitational-wave signals
with larger amplitudes, as well as higher frequencies in the case of a
more compact nascent neutron star. After the prompt shock-breakout burst
of electron neutrinos, a more compact accreting remnant produces higher
neutrino luminosities and higher mean neutrino energies. The observable
neutrino emission in the SASI sloshing direction exhibits a modulation
of several ten percent in the luminosities and around 1 MeV in the mean
energies with most power at typical SASI frequencies between roughly 20
and 100 Hz. The modulation is caused by quasi-periodic variations in the
mass accretion rate of the neutron star in each hemisphere. At times
later than ~50-100 ms after bounce, the gravitational-wave amplitude
is dominated by the growing low-frequency (⪉200 Hz) signal associated
with anisotropic neutrino emission. A high-frequency wave signal results
from nonradial gas flows in the outer layers of the anisotropically
accreting neutron star. Right after bounce such nonradial mass motions
occur due to prompt post-shock convection in both considered cases and
contribute mostly to the early wave production around 100 Hz. Later they
are instigated by the SASI and by convective overturn that vigorously
stir the neutrino-heating and cooling layers, and also by convective
activity developing below the neutrinosphere. The gravitational-wave
power then peaks at about 300-800 Hz, connected to changes in the mass
quadrupole moment on a timescale of milliseconds. Distinctively higher
spectral frequencies originate from the more compact and more rapidly
contracting neutron star. Both the neutrino and gravitational-wave
emission therefore carry information that is characteristic of the
properties of the nuclear equation of state in the hot remnant. The
detectability of the SASI effects in the neutrino and gravitational-wave
signals is briefly discussed.
---------------------------------------------------------
Title: Cool Gas in the Magellanic Stream
Authors: Matthews, D.; Staveley-Smith, L.; Dyson, P.; Muller, E.
2009ApJ...691L.115M Altcode: 2009arXiv0901.3415M
We present the first direct detection of cold atomic gas in the
Magellanic Stream, through 21 cm line absorption toward a background
radio source, J0119-6809, using the Australia Telescope Compact
Array. Two absorption components were identified at heliocentric
velocities 218.6 km s<SUP>-1</SUP> and 227.0 km s<SUP>-1</SUP>, with
optical depths of τ ≈ 0.02. The corresponding H I emission region has
a column density in excess of 2 × 10<SUP>20</SUP> cm<SUP>-2</SUP>. The
inferred spin temperature of the emitting gas is ~70 K. We failed
to find cool gas in observations of three other radio continuum
sources. Although we have definitively detected cool gas in the Stream,
its spin temperature is higher than similar components in the LMC, SMC,
and Bridge, and its contribution to the total H I density is probably
lower. No corresponding <SUP>12</SUP>CO(J = 1→ 0) or dust appears
to be associated with the cool gas, suggesting that the cloud is not
forming stars.
---------------------------------------------------------
Title: Cluster magnetic fields from galactic outflows
Authors: Donnert, J.; Dolag, K.; Lesch, H.; Müller, E.
2009MNRAS.392.1008D Altcode: 2008arXiv0808.0919D
We performed cosmological, magnetohydrodynamical simulations to follow
the evolution of magnetic fields in galaxy clusters, exploring the
possibility that the origin of the magnetic seed fields is galactic
outflows during the starburst phase of galactic evolution. To do
this, we coupled a semi-analytical model for magnetized galactic
winds as suggested by Bertone, Vogt & Enßlin to our cosmological
simulation. We find that the strength and structure of magnetic fields
observed in galaxy clusters are well reproduced for a wide range of
model parameters for the magnetized, galactic winds and do only weakly
depend on the exact magnetic structure within the assumed galactic
outflows. Although the evolution of a primordial magnetic seed field
shows no significant differences to that of galaxy cluster fields
from previous studies, we find that the magnetic field pollution in
the diffuse medium within filaments is below the level predicted by
scenarios with pure primordial magnetic seed field. We therefore
conclude that magnetized galactic outflows and their subsequent
evolution within the intracluster medium can fully account for the
observed magnetic fields in galaxy clusters. Our findings also suggest
that measuring cosmological magnetic fields in low-density environments
such as filaments is much more useful than observing cluster magnetic
fields to infer their possible origin.
---------------------------------------------------------
Title: The Dust-to-Gas Ratio in the Small Magellanic Cloud Tail
Authors: Gordon, K. D.; Bot, C.; Muller, E.; Misselt, K. A.; Bolatto,
A.; Bernard, J. -P.; Reach, W.; Engelbracht, C. W.; Babler, B.;
Bracker, S.; Block, M.; Clayton, G. C.; Hora, J.; Indebetouw, R.;
Israel, F. P.; Li, A.; Madden, S.; Meade, M.; Meixner, M.; Sewilo,
M.; Shiao, B.; Smith, L. J.; van Loon, J. Th.; Whitney, B. A.
2009ApJ...690L..76G Altcode: 2008arXiv0811.2789G
The Tail region of the Small Magellanic Cloud (SMC) was imaged using the
MIPS instrument on the Spitzer Space Telescope as part of the SAGE-SMC
Spitzer Legacy. Diffuse infrared emission from dust was detected in
all the MIPS bands. The Tail gas-to-dust ratio was measured to be 1200
± 350 using the MIPS observations combined with existing IRAS and
H I observations. This gas-to-dust ratio is higher than the expected
500-800 from the known Tail metallicity indicating possible destruction
of dust grains. Two cluster regions in the Tail were resolved into
multiple sources in the MIPS observations and local gas-to-dust ratios
were measured to be ~ 440 and ~ 250 suggest dust formation and/or
significant amounts of ionized gas in these regions. These results
support the interpretation that the SMC Tail is a tidal Tail recently
stripped from the SMC that includes gas, dust, and young stars.
---------------------------------------------------------
Title: A new general relativistic magnetohydrodynamics code for
dynamical spacetimes
Authors: Cerdá-Durán, P.; Font, J. A.; Antón, L.; Müller, E.
2008A&A...492..937C Altcode: 2008arXiv0804.4572C
We present a new numerical code that solves the general relativistic
magneto-hydrodynamical (GRMHD) equations coupled to the Einstein
equations for the evolution of a dynamical spacetime within a
conformally-flat approximation. This code has been developed with the
main objective of studying astrophysical scenarios in which both,
high magnetic fields and strong gravitational fields appear, such
as the magneto-rotational collapse of stellar cores, the collapsar
model of GRBs, and the evolution of neutron stars. The code is based
on an existing and thoroughly tested purely hydrodynamical code and
on its extension to accommodate weakly magnetized fluids (passive
magnetic-field approximation). These codes have been applied in the
past to simulate the aforementioned scenarios with increasing levels of
sophistication in the input physics. The numerical code we present here
is based on high-resolution shock-capturing schemes to solve the GRMHD
equations, which are cast in first-order, flux-conservative hyperbolic
form, together with the flux constraint transport method to ensure the
solenoidal condition of the magnetic field. Since the astrophysical
applications envisaged do not deviate significantly from spherical
symmetry, the conformal flatness condition approximation is used for
the formulation of the Einstein equations; this has repeatedly shown to
yield very good agreement with full general relativistic simulations of
core-collapse supernovae and the evolution of isolated neutron stars. In
addition, the code can handle several equations of state, from simple
analytical expressions to microphysical tabulated ones. In this paper we
present stringent tests of our new GRMHD numerical code, which show its
ability to handle all aspects appearing in the astrophysical scenarios
for which the code is intended, namely relativistic shocks, highly
magnetized fluids, and equilibrium configurations of magnetized neutron
stars. As an application, magneto-rotational core-collapse simulations
of a realistic progenitor are presented and the results compared with
our previous findings in the passive magnetic-field approximation.
---------------------------------------------------------
Title: The core helium flash revisited. I. One and two-dimensional
hydrodynamic simulations
Authors: Mocák, M.; Müller, E.; Weiss, A.; Kifonidis, K.
2008A&A...490..265M Altcode: 2008arXiv0805.1355M
Context: We investigate the hydrodynamics of the core helium flash
close to its peak. Past research concerned with the dynamics of this
event is inconclusive. However, the most recent multidimensional
hydrodynamic studies suggest a quiescent behavior and seem to rule out
an explosive scenario. <BR />Aims: Depending on initial conditions,
turbulence models, grid resolution, and dimensionality of the
simulation, previous work indicated that the core helium flash could
lead either to the disruption of a low-mass star or to a quiescent
quasi-hydrostatic evolution. We attempt to clarify this issue by
simulating the evolution with advanced numerical methods and detailed
microphysics. <BR />Methods: Assuming spherical or axial symmetry,
we simulate the evolution of the helium core of a 1.25~M<SUB>⊙</SUB>
star with a metallicity Z=0.02 during the core helium flash at its peak
with a grid-based hydrodynamical code. <BR />Results: We find that the
core helium flash neither rips the star apart, nor significantly alters
its structure, since convection plays a crucial role in keeping the
star in hydrostatic equilibrium. In addition, our simulations indicate
the presence of overshooting, which implies new predictions concerning
mixing of chemical species in red giants.
---------------------------------------------------------
Title: Exploring the relativistic regime with Newtonian
hydrodynamics. II. An effective gravitational potential for rapid
rotation
Authors: Müller, B.; Dimmelmeier, H.; Müller, E.
2008A&A...489..301M Altcode: 2008arXiv0802.2459M
We present the generalization of a recently introduced <P />modified
gravitational potential for self-gravitating fluids. The <P />use of
this potential allows for an accurate approximation of <P />general
relativistic effects in an otherwise Newtonian hydrodynamics <P />code
also in cases of rapid rotation. We test this approach in <P />numerical
simulations of astrophysical scenarios related to compact <P />stars,
like supernova core collapse with both a simplified and <P />detailed
microphysical description of matter, and rotating neutron <P />stars
in equilibrium. We assess the quality of the new potential, <P />and
demonstrate that it provides a significant improvement compared <P
/>to previous formulations for such potentials. Newtonian simulations
<P />of compact objects employing such an effective relativistic <P
/>potential predict inaccurate pulsation frequencies despite the <P
/>excellent agreement of the collapse dynamics and structure of the
<P />compact objects with general relativistic results. We analyze
and <P />discuss the reason for this behavior.
---------------------------------------------------------
Title: The ALFA Zone of Avoidance Survey
Authors: Henning, P. A.; Springob, C. M.; Day, F.; Minchin, R.;
Momjian, E.; Catinella, B.; Muller, E.; Koribalski, B.; Masters,
K.; Pantoja, C.; Putman, M.; Rosenberg, J. L.; Schneider, S.;
Staveley-Smith, L.
2008AIPC.1035..246H Altcode:
The Arecibo L-Band Feed Array (ALFA) Zone of Avoidance (ZOA) team
is mapping the distribution of low-Galactic-latitude galaxies and
large-scale structures through detection of galaxies'21-cm emission with
ALFA. This ZOA survey finds new HI galaxies which lie hidden behind
the Milky Way, and also provides redshifts for partially-obscured
galaxies known at other wavelengths. Two precursor regions which
straddle the Galactic plane have been observed to date, totalling
140 square degrees, with 72 HI galaxies detected. Detections through
the inner Galaxy generally have no cataloged counterparts in any other
waveband, due to the heavy extinction and stellar confusion. Detections
through the outer Galaxy are more likely to have 2MASS counterparts,
and we provide redshifts for these galaxies. A third region, through
the Taurus molecular cloud, has also been observed. The full ALFA ZOA
survey will reveal more previously unknown galaxies and map low-latitude
large-scale structures.
---------------------------------------------------------
Title: The ALFA Zone of Avoidance Survey: Results from the Precursor
Observations
Authors: Springob, C. M.; Henning, P. A.; Catinella, B.; Day, F.;
Minchin, R.; Momjian, E.; Koribalski, B.; Masters, K. L.; Muller,
E.; Pantoja, C.; Putman, M.; Rosenberg, J. L.; Schneider, S.;
Staveley-Smith, L.
2008IAUS..244..383S Altcode: 2007IAUS..244..383S; 2007arXiv0708.1724S
The Arecibo L-band Feed Array Zone of Avoidance Survey (ALFA ZOA)
will map 1350-1800 deg<SUP>2</SUP> at low Galactic latitude, providing
HI spectra for galaxies in regions of the sky where our knowledge of
local large scale structure remains incomplete, owing to obscuration
from dust and high stellar confusion near the Galactic plane. Because
of these effects, a substantial fraction of the galaxies detected in
the survey will have no optical or infrared counterparts. However,
near infrared follow up observations of ALFA ZOA sources found in
regions of lowest obscuration could reveal whether some of these
sources could be objects in which little or no star formation has
taken place (“dark galaxies”). We present here the results of
ALFA ZOA precursor observations on two patches of sky totaling 140
deg<SUP>2</SUP> (near l = 40°, and l = 192°). We have measured HI
parameters for detections from these observations, and cross-correlated
with the NASA/IPAC Extragalactic Database (NED). A significant fraction
of the objects have never been detected at any wavelength. For those
galaxies that have been previously detected, a significant fraction
have no previously known redshift, and no previous HI detection.
---------------------------------------------------------
Title: The Arecibo Galaxy Environment Survey Potential for finding
Dark Galaxies and Results so far
Authors: Minchin, R. F.; Auld, R.; Cortese, L.; Davies, J. I.; Momjian,
E.; Taylor, R.; Catinella, B.; Henning, P.; Linder, S.; Muller, E.;
O'Neil, K.; Rosenberg, J.; Sabatini, S.; Schneider, S. E.; Stage,
M.; van Driel, W.; van Driel
2008IAUS..244..112M Altcode: 2007IAUS..244..112M
The Arecibo Galaxy Environment Survey is a blind neutral hydrogen
survey using the ALFA multibeam receiver at Arecibo Observatory to reach
unprecedented sensitivities in a number of selected fields in the local
Universe. When completed the survey will cover 200 square degrees out
to a distance of at least 270 Mpc. If a population of gas-rich dark
galaxies exists, then this survey is in a prime position to uncover
that population. <P />So far 20 square degrees have been covered in the
regions of Abell 1367, the Virgo Cluster, the NGC 7332/9 galaxy pair
and the isolated galaxy NGC 1156. Over 200 sources have been found,
including a number that have no obvious optical counterparts. We
discuss here the potential of AGES for uncovering more such objects
and the characteristics of the dark sources identified to date.
---------------------------------------------------------
Title: Large Scale Structure and Turbulence: The Mopra G333 Survey
Authors: Cunningham, M.; Lo, N.; Kramer, C.; Bains, I.; Jones, P.;
Burton, M.; Muller, E.; Ossenkopf, V.
2008EAS....31....9C Altcode:
We have used the new broadband capabilities of the Mopra telescope
to map the distribution of 26 different molecular transitions in
an approximately 1 degree square region of the southern Galactic
plane (the G333/RCW106 giant molecular cloud complex). The aim is to
addresss observationally some of the key questions about the dynamical
processes surrounding massive star formation (e.g. massive stellar
winds and large-scale galactic flows) and their relative importance in
regulating the star formation process. These dynamical processes help
drive the turbulent motions, which are ubiquitous in giant molecular
clouds (GMCs). The multi-molecular line nature of this survey is what
distinguishes it from similar surveys and is crucial for gaining a
clear picture of the energetics and dynamics of the gas. Investigating
and understanding the chemistry of this region is a necessary part of
the project if the molecular line observations are to be interpreted
physically.
---------------------------------------------------------
Title: Atomic Gas Associated with GMCs in the LMC
Authors: Hughes, Annie; Wong, T.; Ott, J.; Muller, E.; Pineda, J. L.;
Mizuno, Y.
2008ASSP....5..293H Altcode: 2008glv..book..293H
No abstract at ADS
---------------------------------------------------------
Title: An Observational Study of the GMCs in the Magellanic Clouds
in Millimeter and Submillimeter Wavelengths
Authors: Minamidani, T.; Mizuno, N.; Mizuno, Y.; Kawamura, A.;
Onishi, T.; Hasegawa, T.; Tatematsu, K.; Ikeda, M.; Moriguchi, Y.;
Yamaguchi, N.; Ott, J.; Wong, T.; Muller, E.; Pineda, J. L.; Hughes,
A.; Staveley-Smith, L.; Klein, U.; Mizuno, A.; Nikolić, S.; Booth,
R. S.; Heikkilä, A.; Nyman, L. -Å.; Lerner, M.; Garay, G.; Kim,
S.; Rubio, M.; Fukui, Y.
2008ASSP....5..311M Altcode: 2008glv..book..311M
No abstract at ADS
---------------------------------------------------------
Title: Multidimensional hydrodynamic simulations of the core helium
flash .
Authors: Mocak, M.; Müller, E.; Weiss, A.; Kifonidis, K.
2008MmSAI..79..729M Altcode:
Using an initial model, which is obtained from the evolution of a
1.25 M<SUB>⊙</SUB> star with a metallicity of 0.02 computed with
the Garching stellar evolution code, we investigate the hydrodynamics
of the core helium flash near its peak. Past research concerned with
the dynamics of the core helium flash is inconclusive. Its results
range from a confirmation of the standard picture, where the star
remains in hydrostatic equilibrium during the flash \citet{deu96},
up to a disruption of the star \citet{edw69}. However, the most
recent multidimensional hydrodynamic study \citet{dea06} suggests a
quiescent behavior during the flash and seems to rule out an explosive
scenario. Here we present the first results of a new comprehensive
study of the core helium flash, which seem to confirm this qualitative
behavior.
---------------------------------------------------------
Title: Hα Emission from the Magellanic Bridge
Authors: Muller, E.; Parker, Q. A.
2007PASA...24...69M Altcode: 2007arXiv0706.4037M
We present here a preliminary report and commentary of recently
processed observations of Hα emission towards the Magellanic
Bridge. These data have been analysed in an attempt to quantify the
extent to which the stellar population is capable of reshaping the
local ISM. We find that the Hα emission regions are small, weak
and sparsely distributed, consistent with a relatively quiescent and
inactive ISM where radiative and collisional ionisation is inefficient
and sporadic. This suggests that energetic processes at the small scale
(i.e. ~tens of pc) do not dominate the energy balance within the ISM
of the Bridge, which therefore hosts a pristine turbulent structure,
otherwise inaccessible within our own Galaxy. We find Hα emission that
is well correlated with detected <SUP>12</SUP>CO(1-0) line emission
(a proxy for molecular hydrogen), as well as other easily identified
ring-like Hi features.
---------------------------------------------------------
Title: Generic Gravitational-Wave Signals from the Collapse of
Rotating Stellar Cores
Authors: Dimmelmeier, H.; Ott, C. D.; Janka, H. -T.; Marek, A.;
Müller, E.
2007PhRvL..98y1101D Altcode: 2007astro.ph..2305D
We perform general relativistic (GR) simulations of stellar core
collapse to a protoneutron star, using a microphysical equation of
state (EOS) and an approximation of deleptonization. We show that for
a wide range of rotation rates and profiles the gravitational-wave (GW)
burst signals from the core bounce are generic, known as type I. In our
systematic study, using both GR and Newtonian gravity, we identify and
quantify the influence of rotation, the EOS, and deleptonization on
this result. Such a generic type of signal templates will facilitate
a more efficient search in current and future GW detectors of both
interferometric and resonant type.
---------------------------------------------------------
Title: The Arecibo Galaxy Environments Survey - Description of the
Survey and Early Results
Authors: Minchin, R. F.; Auld, R.; Davies, J. I.; Catinella,
B.; Cortese, L.; Linder, S.; Momjian, E.; Muller, E.; O'Neil, K.;
Rosenberg, J.; Sabatini, S.; Schneider, S. E.; Stage, M.; van Driel,
W.; AGES Team
2007IAUS..235..227M Altcode: 2006astro.ph.10629M; 2006IAUS..235E.284M
The Arecibo Galaxy Envrionments Survey (AGES) is a 2000-hour neutral
hydrogen survey using the new Arecibo L-band Feed Array multibeam
instrument at Arecibo Observatory. It covers 200 square degrees of
sky, sampling a range of environments from the Local Void through
to the Virgo Cluster with higher sensitivity, spatial resolution and
velocity resolution than previous neutral hydrogen surveys. AGES will
address a number of scientific objectives, including: 1. The HI mass
function in different environments. 2. Baryonic mass density. 3. HVCs,
dwarf galaxies etc. 4. Tidal features. 5. Dynamical masses. 6. Low
column density HI. 7. Isolated HI clouds - dark galaxies. 8. HI
and QSO absorption features. 9. Spatial distribution of HI selected
galaxies The first field to be covered, 5 square degrees centred on
the optically-isolated galaxy NGC 1156, has revealed at least two
new companions to NGC 1156, one of which may be interacting with the
galaxy. This field also contains 51 definite detections in the volume
beyond NGC 1156, including one with no optical counterpart. A further
30 candidates have been identified for follow-up observations.
---------------------------------------------------------
Title: Convective processes and hydromagnetic instabilities in core
collapse supernova simulations
Authors: Obergaulinger, M.; Hammer, N. J.; Müller, E.
2007IAUS..239..323O Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Internal shocks in relativistic outflows: collisions of
magnetized shells
Authors: Mimica, P.; Aloy, M. A.; Müller, E.
2007A&A...466...93M Altcode: 2006astro.ph.11765M
Aims: We study the collision of magnetized irregularities (shells) in
relativistic outflows in order to explain the origin of the generic
phenomenology observed in the non-thermal emission of both blazars
and gamma-ray bursts. We focus on the influence of the magnetic field
on the collision dynamics, and we investigate how the properties
of the observed radiation depend on the strength of the initial
magnetic field and on the initial internal energy density of the
flow. <BR />Methods: The collisions of magnetized shells and the
radiation resulting from these collisions are calculated using the 1D
relativistic magnetohydrodynamics code MRGENESIS. The interaction of
the shells with the external medium prior to their collision is also
determined using an exact solver for the corresponding 1D relativistic
magnetohydrodynamic Riemann problem. In both cases we assume that the
magnetic field is oriented perpendicular to the flow direction. <BR
/>Results: Our simulations show that two magnetization parameters
- the ratio of magnetic energy density and thermal energy density,
α<SUB>B</SUB>, and the ratio of magnetic energy density and mass-energy
density, σ - play an important role in the pre-collision phase, while
the dynamics of the collision and the properties of the light curves
depend mostly on the magnetization parameter σ. Comparing synthetic
light curves computed from hydrodynamic and magnetohydrodynamic models
we find that the assumption commonly made in the former models that
the magnetization parameter α<SUB>B</SUB> is constant and uniform,
holds rather well, if α<SUB>B</SUB> < 0.01. The interaction of the
shells with the external medium changes the flow properties at their
edges prior to the collision. For sufficiently dense shells moving
at large Lorentz factors (≳25) these properties depend only on the
magnetization parameter σ. Internal shocks in GRBs may reach maximum
efficiencies of conversion of kinetic into thermal energy between 6%
and 10%, while in case of blazars, the maximum efficiencies are ~2%.
---------------------------------------------------------
Title: Analysis of the Neutrino Antineutrino Annihilation near
Accreting Stellar Black Holes
Authors: Birkl, R.; Aloy, M. A.; Janka, H. -Th.; Müller, E.
2007sgrb.conf...11B Altcode:
We investigate the deposition of energy and momentum due to the
annihilation of neutrinos (ν) and antineutrinos (barν) in the
vicinity of steady, axisymmetric accretion tori around stellar-mass
black holes (BHs). This process is widely considered as an energy source
for driving ultrarelativistic outflows with the potential to produce
gamma-ray bursts. We analyze the influence of general relativistic
(GR) effects in combination with different neutrinosphere properties
on the νbarν-annihilation efficiency and spatial distribution of
the energy deposition rate. Assuming axial symmetry, we numerically
compute the annihilation rate 4-vector. For this purpose, we construct
the local neutrino distribution by ray-tracing neutrino trajectories
in a Kerr space-time using null geodesics. We vary the value of
the dimensionless specific angular momentum a of the central BH,
which provides the gravitational field in our models. We also study
different shapes of the neutrinospheres, spheres, thin disks, and
thick accretion tori, whose structure ranges from idealized tori to
equilibrium non-selfgravitating matter distributions. Furthermore,
we compute Newtonian models where the influence of the gravitational
field on the annihilation process is neglected. Results: Compared to
Newtonian calculations, GR effects increase the total annihilation
rate measured by an observer at infinity by a factor of two when the
neutrinosphere is a thin disk, but the increase is only ≈25% for
toroidal and spherical neutrinospheres. Comparing cases with similar
luminosities, thin disk models yield the highest energy deposition rates
by νbarν-annihilation, and spherical neutrinospheres the lowest ones,
independently of whether GR effects are included. Increasing a from
0 to 1 enhances the energy deposition rate measured by an observer at
infinity by roughly a factor of 2 due to the change of the inner radius
of the neutrinosphere. General relativity and rotation cause important
differences in the spatial distri bution of the energy deposition rate
by νbarν-annihilation.
---------------------------------------------------------
Title: Commission 35: Stellar Constitution
Authors: Dziembowski, Wojciech A.; D'Antona, Francesca; Charbonnel,
C.; Christensen-Dalsgaard, J.; Guzik, J.; Langer, N.; Larson, R.;
Liebert, J.; Meynet, G.; Müller, E.; Saio, H.; Vandenberg, D.
2007IAUTA..26..205D Altcode:
Ihe triennial report from Commission 35 covers its organizational
activities and highlights accomplishments in various topics of stellar
interior physics.
---------------------------------------------------------
Title: Neutrino pair annihilation near accreting, stellar-mass
black holes
Authors: Birkl, R.; Aloy, M. A.; Janka, H. -Th.; Müller, E.
2007A&A...463...51B Altcode: 2006astro.ph..8543B
Context: We investigate the deposition of energy and momentum due to the
annihilation of neutrinos (ν) and antineutrinos (barν) in the vicinity
of steady, axisymmetric accretion tori around stellar-mass black holes
(BHs). This process is widely considered as an energy source for driving
ultrarelativistic outflows with the potential to produce gamma-ray
bursts. <BR />Aims: We analyze the influence of general relativistic
(GR) effects in combination with different neutrinosphere properties
on the νbarν-annihilation efficiency and spatial distribution of
the energy deposition rate. <BR />Methods: Assuming axial symmetry, we
numerically compute the annihilation rate 4-vector. For this purpose,
we construct the local neutrino distribution by ray-tracing neutrino
trajectories in a Kerr space-time using null geodesics. We vary the
value of the dimensionless specific angular momentum a of the central
BH, which provides the gravitational field in our models. We also
study different shapes of the neutrinospheres, spheres, thin disks,
and thick accretion tori, whose structure ranges from idealized tori
to equilibrium non-selfgravitating matter distributions. Furthermore,
we compute Newtonian models where the influence of the gravitational
field on the annihilation process is neglected. <BR />Results: Compared
to Newtonian calculations, GR effects increase the total annihilation
rate measured by an observer at infinity by a factor of two when the
neutrinosphere is a thin disk, but the increase is only ≈25% for
toroidal and spherical neutrinospheres. Comparing cases with similar
luminosities, thin disk models yield the highest energy deposition rates
by νbarν-annihilation, and spherical neutrinospheres the lowest ones,
independently of whether GR effects are included. Increasing a from
0 to 1 enhances the energy deposition rate measured by an observer at
infinity by roughly a factor of 2 due to the change of the inner radius
of the neutrinosphere. General relativity and rotation cause important
differences in the spatial distribution of the energy deposition rate
by νbarν-annihilation.
---------------------------------------------------------
Title: Turbulence in the G333 molecular cloud
Authors: Jones, P. A.; Cunningham, M. R.; Bains, I.; Muller, E.;
Wong, T.; Burton, M. G.
2007IAUS..237..429J Altcode: 2006IAUS..237E.138J
We present some first results of the analysis of turbulence in the
G333 molecular cloud complex. Observations were obtained for 3-mm
transitions of ^ 13CO, C^18O, CS and C^34S with the Mopra telescope,
with a resolution around 35 arcsec. Up to 16 other transitions will
be mapped simultaneously in the 2006 season. An area 1 x 1.5 degree
was mapped in ^13CO, and the other weaker tracers mapped in the dense
regions to obtain complementary information from tracers of different
critical density. Here we present some results from power spectra and
velocity-component analysis.
---------------------------------------------------------
Title: The Arecibo galaxy environment survey - a sensitive survey
for neutral hydrogen in the local Universe
Authors: Minchin, R.; Auld, R.; Cortese, L.; Davies, J.; Momjian,
E.; Taylor, R.; Catinella, B.; Henning, P.; Linder, S.; Muller, E.;
O'Neil, K.; Rosenberg, J.; Sabatini, S.; Schneider, S.; Stage, M.;
van Driel, W.
2007mru..confE..27M Altcode: 2007PoS....52E..27M
No abstract at ADS
---------------------------------------------------------
Title: The ALFA Zone of Avoidance Survey: Results from the Precursor
Observations
Authors: Springob, Chris M.; Henning, P. A.; Catinella, B.; Day, F.;
Minchin, R.; Momjian, E.; Koribalski, B.; Masters, K. L.; Muller,
E.; Pantoja, C.; Putman, M.; Rosenberg, J. L.; Schneider, S.;
Staveley-Smith, L.
2006AAS...209.9504S Altcode: 2006BAAS...38Q1034S
We present new extragalactic 21 cm observations in the Galactic
Plane region. These observations are a precursor to a large scale,
extragalactic, zone of avoidance survey with the Arecibo L-band Feed
Array (ALFA). The data for this survey are being taken concurrently
with a Galactic survey and a pulsar survey. Full survey observations,
which will begin in 2007, will reveal local large scale structure in
a part of the extragalactic sky that is relatively unexplored due to
the obscuration of optical light by dust in our Galaxy. One of these
surveys will have an integration time of 268 seconds per point in the
inner Galaxy and 134 seconds in the outer Galaxy, covering |b|<5
degrees, while the other will have an integration time of only 5 seconds
per point, covering |b|<10 degrees with an rms of roughly 6 mJy. No
other extragalactic ALFA survey will cover these latitudes. Precursor
observations have been taken using the latter observational setup on
two patches of sky totaling 140 square degrees (one near l=40 degrees,
and the other near l=192 degrees). We have measured HI parameters
for detections from these observations, and cross-correlated with
the NASA/IPAC Extragalactic Database. A significant fraction of the
objects are new, having never been detected at any wavelength. For
those galaxies that have been previously detected, the majority have
no previously known redshift, and and no previous HI detection. This
research was performed while C.M.S. held a National Research Council
Research Associateship Award at the Naval Research Laboratory. Basic
research in astronomy at the Naval Research Laboratory is funded by the
Office of Naval Research. P.A.H. acknowledges support from NSF grant
AST-0506676. The Arecibo Observatory is part of the National Astronomy
and Ionosphere Center, which is operated by Cornell University under
a cooperative agreement with the National Science Foundation.
---------------------------------------------------------
Title: Earthwalk
Authors: Muller, E.
2006AGUFMED11A1183M Altcode:
When the weather is nice, I like to take my students on a walk to the
center of the earth. Earthwalk is a hands-on and feet-on activity
that gets students outdoors, having fun, moving and learning about
the structures of the earth. Earthwalk is a lesson to help students
visualize our planets size and scale. This activity has students
calculate the ratio of a scaled 100m cross-sectional earth, mark the
boundaries between major planetary layers, walk from the center of
the earth to the surface and draw proportional manmade and natural
surface features (mountains, building, mine shafts, etc). This lesson
effectively integrates content and pedagogy while touching on skills and
topics such as math, measurement, science, writing skills (they have
to take notes), reading, listening and group dynamics. This activity
fits well into the earth science curriculum by introducing basic
seismology; tectonic, geochemistry and heat transfer concepts. Besides
showcasing this lesson, a limited number of Earth Anatomy posters will
be distributed.
---------------------------------------------------------
Title: The Arecibo Galaxy Environment Survey: precursor observations
of the NGC 628 group
Authors: Auld, R.; Minchin, R. F.; Davies, J. I.; Catinella, B.;
van Driel, W.; Henning, P. A.; Linder, S.; Momjian, E.; Muller, E.;
O'Neil, K.; Sabatini, S.; Schneider, S.; Bothun, G.; Cortese, L.;
Disney, M.; Hoffman, G. L.; Putman, M.; Rosenberg, J. L.; Baes, M.;
de Blok, W. J. G.; Boselli, A.; Brinks, E.; Brosch, N.; Irwin, J.;
Karachentsev, I. D.; Kilborn, V. A.; Koribalski, B.; Spekkens, K.
2006MNRAS.371.1617A Altcode: 2006MNRAS.tmp..953A; 2006astro.ph..7452A
The Arecibo Galaxy Environment Survey (AGES) is one of several HI
surveys utilizing the new Arecibo L-band Feed Array (ALFA) fitted
to the 305-m radio telescope at Arecibo.<SUP>a</SUP> The survey is
specifically designed to investigate various galactic environments
to higher sensitivity, higher velocity resolution and higher spatial
resolution than previous fully sampled, 21-cm multibeam surveys. The
emphasis is on making detailed observations of nearby objects although
the large system bandwidth (100MHz) will allow us to quantify the HI
properties over a large instantaneous velocity range. <P />In this
paper, we describe the survey and its goals and present the results
from the precursor observations of a 5 × 1-deg<SUP>2</SUP> region
containing the nearby (~10Mpc) NGC 628 group. We have detected all the
group galaxies in the region including the low-mass (M<SUB>HI</SUB>
~10<SUP>7</SUP>M<SUB>solar</SUB>) dwarf, dw0137+1541. The fluxes and
velocities for these galaxies compare well with previously published
data. There is no intragroup neutral gas detected down to a limiting
column density of 2 × 10<SUP>18</SUP>cm<SUP>-2</SUP>. <P />In addition
to the group galaxies we have detected 22 galaxies beyond the NGC
628 group, nine of which are previously uncatalogued. We present the
HI data for these objects and also SuperCOSMOS images for possible
optical galaxies that might be associated with the HI signal. We have
used V/V<SUB>max</SUB> analysis to model how many galaxies beyond
1000kms<SUP>-1</SUP> should be detected and compare this with our
results. The predicted number of detectable galaxies varies depending
on the HI mass function (HIMF) used in the analysis. Unfortunately
the precursor survey area is too small to determine whether this is
saying anything fundamental about the HIMF or simply highlighting the
effect of low number statistics. This is just one of many questions
that will be addressed by the complete AGES survey.
---------------------------------------------------------
Title: Axisymmetric simulations of magnetorotational core collapse:
approximate inclusion of general relativistic effects
Authors: Obergaulinger, M.; Aloy, M. A.; Dimmelmeier, H.; Müller, E.
2006A&A...457..209O Altcode: 2006astro.ph..2187O
We continue our investigations of the magnetorotational collapse of
stellar cores by discussing simulations performed with a modified
Newtonian gravitational potential that mimics general relativistic
effects. The approximate TOV gravitational potential used in our
simulations captures several basic features of fully relativistic
simulations quite well. In particular, it is able to correctly reproduce
the behavior of models that show a qualitative change both of the
dynamics and the gravitational wave signal when switching from Newtonian
to fully relativistic simulations. For models where the dynamics
and gravitational wave signals are already captured qualitatively
correctly by a Newtonian potential, the results of the Newtonian and
the approximate TOV models differ quantitatively. The collapse proceeds
to higher densities with the approximate TOV potential, allowing for
a more efficient amplification of the magnetic field by differential
rotation. The strength of the saturation fields (∼ 10<SUP>15</SUP>
~ G at the surface of the inner core) is a factor of two to three
higher than in Newtonian gravity. Due to the more efficient field
amplification, the influence of magnetic fields is considerably more
pronounced than in the Newtonian case for some of the models. As in
the Newtonian case, sufficiently strong magnetic fields slow down
the core's rotation and trigger a secular contraction phase to higher
densities. More clearly than in Newtonian models, the collapsed cores
of these models exhibit two different kinds of shock generation. Due
to magnetic braking, a first shock wave created during the initial
centrifugal bounce at subnuclear densities does not suffice for
ejecting any mass, and the temporarily stabilized core continues to
collapse to supranuclear densities. Another stronger shock wave is
generated during the second bounce as the core exceeds nuclear matter
density. The gravitational wave signal of these models does not fit
into the standard classification. Therefore, in the first paper of this
series we introduced a new type of gravitational wave signal, which we
call type IV or “magnetic type”. This signal type is more frequent
for the approximate relativistic potential than for the Newtonian
one. Most of our weak-field models are marginally detectable with the
current LIGO interferometer for a source located at a distance of 10
kpc. Strongly magnetized models emit a substantial fraction of their
GW power at very low frequencies. A flat spectrum between 10 Hz and
⪉ 100 kHz denotes the generation of a jet-like hydromagnetic outflow.
---------------------------------------------------------
Title: Multidimensional supernova simulations with approximative
neutrino transport. I. Neutron star kicks and the anisotropy of
neutrino-driven explosions in two spatial dimensions
Authors: Scheck, L.; Kifonidis, K.; Janka, H. -Th.; Müller, E.
2006A&A...457..963S Altcode: 2006astro.ph..1302S
We study hydrodynamic instabilities during the first seconds of
core-collapse supernovae by means of 2D simulations with approximative
neutrino transport and boundary conditions that parameterize the
effects of the contracting neutron star and allow us to obtain
sufficiently strong neutrino heating and, hence, neutrino-driven
explosions. Confirming more idealised studies, as well as supernova
simulations with spectral transport, we find that random seed
perturbations can grow by hydrodynamic instabilities to a globally
asymmetric mass distribution in the region between the nascent neutron
star and the accretion shock, leading to a dominance of dipole (l=1)
and quadrupole (l=2) modes in the explosion ejecta, provided the onset
of the supernova explosion is sufficiently slower than the growth time
scale of the low-mode instability. By gravitational and hydrodynamic
forces, the anisotropic mass distribution causes an acceleration of the
nascent neutron star, which lasts for several seconds and can propel the
neutron star to velocities of more than 1000 km s<SUP>-1</SUP>. Because
the explosion anisotropies develop chaotically and change by small
differences in the fluid flow, the magnitude of the kick varies
stochastically. No systematic dependence of the average neutron star
velocity on the explosion energy or the properties of the considered
progenitors is found. Instead, the anisotropy of the mass ejection,
and hence of the kick, seems to increase when the nascent neutron
star contracts more quickly, and thus low-mode instabilities can
grow more rapidly. Our more than 70 models separate into two groups,
one with high and the other with low neutron star velocities and
accelerations after one second of post-bounce evolution, depending
on whether the l=1 mode is dominant in the ejecta or not. This leads
to a bimodality of the distribution when the neutron star velocities
are extrapolated to their terminal values. Establishing a link to the
measured distribution of pulsar velocities, however, requires a much
larger set of calculations and ultimately 3D modelling.
---------------------------------------------------------
Title: Non-spherical core collapse supernovae. II. The late-time
evolution of globally anisotropic neutrino-driven explosions and
their implications for SN 1987 A
Authors: Kifonidis, K.; Plewa, T.; Scheck, L.; Janka, H. -Th.;
Müller, E.
2006A&A...453..661K Altcode: 2005astro.ph.11369K
Two-dimensional simulations of strongly anisotropic supernova explosions
of a nonrotating 15 M<SUB>⊙</SUB> blue supergiant progenitor are
presented, which follow the hydrodynamic evolution from times shortly
after shock formation until hours later. It is shown that explosions
which around the time of shock revival are dominated by low-order
unstable modes (i.e. by a superposition of the l=2 and l=1 modes,
in which the former is strongest), are consistent with all major
observational features of SN 1987 A, in contrast to models which
show high-order mode perturbations only and were published in earlier
work. Among other items, the low-mode models exhibit final iron-group
velocities of up to ∼ 3300 km s<SUP>-1</SUP>, strong mixing at the
He/H composition interface, with hydrogen being mixed downward in
velocity space to only 500 km s<SUP>-1</SUP>, and a final prolate
anisotropy of the inner ejecta with a major to minor axis ratio of
about 1.6. The success of low-mode explosions with an energy of about
2×10<SUP>51</SUP> erg to reproduce these observed features is based
on two effects: the (by 40%) larger initial maximum velocities of
metal-rich clumps compared to our high-mode models, and the initial
global deformation of the shock. The first effect protects the (fastest)
clumps from interacting with the strong reverse shock that forms below
the He/H composition interface, by keeping their propagation timescale
through the He-core shorter than the reverse shock formation time. This
ensures that the outward motion of the clumps remains always subsonic,
and that thus their energy dissipation is minimal (in contrast to the
supersonic case). The second effect is responsible for the strong inward
mixing of hydrogen: the aspherical shock deposits large amounts of
vorticity into the He/H interface layer at early times (around t = 100
s). This triggers the growth of a strong Richtmyer-Meshkov instability
that results in a global anisotropy of the inner ejecta at late times
(i.e. around t = 10 000 s), although the shock itself has long become
spherical by then. The simulations suggest a coherent picture, which
explains the observational data of SN 1987 A within the framework
of the neutrino-driven explosion mechanism using a minimal set of
assumptions. It is therefore argued that other paradigms, which are
based on (more) controversial physics, may not be required to explain
this event.
---------------------------------------------------------
Title: Surveying The Zone Of Avoidance With The Arecibo L-band
Feed Array
Authors: Henning, Patricia A.; Springob, C. M.; Catinella, B.;
Momjian, E.; Koribalski, B.; Masters, K.; Muller, E.; Pantoja, C.;
Putman, M.; Rosenberg, J. L.; Schneider, S.; Staveley-Smith, L.
2006AAS...208.5304H Altcode: 2006BAAS...38..133H
We are conducting 21-cm surveys with the Arecibo L-Band Feed Array,
searching for HI galaxies at low galactic latitudes, where optical
obscuration and infrared confusion preclude the mapping of galaxies
and large-scale structures in those wavebands. Galaxies which contain
HI are detected by these blind surveys, and their Doppler shifted
emission locates them in 3 dimensions.The first survey will be of
the inner Galaxy accessible to Arecibo (l=30-75 degrees), within
10 degrees of the Galactic equator, and will be relatively shallow
(effective integration time of 8-10 seconds per beam, with rms about
6 mJy). We have completed two small regions using this observing mode
(near l=40 degrees, and l=192 degrees). The catalog of HI detections
will be presented, and future expectations for the full survey will be
discussed.We will also be conducting very deep, pointed observations,
with dwell times expected to be more than 260 seconds per pointing,
over all longitudes accessible to Arecibo. Our expectations for this
very deep low Galactic latitude survey will be presented. Both the
shallow and deep surveys are conducted in "commensal" modes with other
surveys on the telescope, a Galactic HI survey, and a pulsar survey,
respectively.P.A.H. acknowledges support from NSF grant AST-0506676.
---------------------------------------------------------
Title: Detection of Molecular Clouds in the Magellanic Bridge:
Candidate Star Formation Sites in a Nearby Low-Metallicity System
Authors: Mizuno, N.; Muller, E.; Maeda, H.; Kawamura, A.; Minamidani,
T.; Onishi, T.; Mizuno, A.; Fukui, Y.
2006ApJ...643L.107M Altcode:
We present the results of a new, wide-field, and broad-ranging
survey for <SUP>12</SUP>CO (1-0) emission regions in the nearest and
brightest tidal structure: the Magellanic Bridge. We have detected
seven sites of <SUP>12</SUP>CO (1-0) emission using the NANTEN
telescope in addition to the one detected previously. The integrated
CO brightness for these detections ranges between 30 and 140 mK km
s<SUP>-1</SUP>, corresponding to an estimated molecular mass of (1-7)
× 10<SUP>3</SUP> M<SUB>solar</SUB> [assuming the CO-to-H<SUB>2</SUB>
conversion factor (X-factor) of ~1.4×10<SUP>21</SUP> cm<SUP>-2</SUP>
(K km s<SUP>-1</SUP>)<SUP>-1</SUP>]. The positions of the CO emission
regions are generally coincident with sites of bright 100 μm emission,
where I<SUB>100μm</SUB>>2.6 MJy sr<SUP>-1</SUP>, and have narrow
line widths of <~2 km s<SUP>-1</SUP>, indicating gas in a cold and
rather quiescent state. The velocity centroids of the CO spectra are
generally consistent with those of the H I spectra, and we suggest
that CO clouds are formed after the tidal encounter, rather than being
extracted from the SMC. This is supported by the small typical lifetime
of CO clouds, which is as short as ~10<SUP>7</SUP> yr and much less
than the estimated 200 Myr age of the Bridge itself.
---------------------------------------------------------
Title: First Results from the Arecibo Galaxy Environment Survey
Authors: Minchin, Robert F.; Auld, R.; Davies, J. I.; Catinella, B.;
Linder, S.; Momjian, E.; Muller, E.; Sabatini, S.; Schneider, S. E.;
Stage, M. D.; van Driel, W.; AGES Team
2006AAS...208.5306M Altcode: 2006BAAS...38R.134M
The Arecibo Galaxy Environment Survey (AGES) is one of several
HI surveys using the new Arecibo L-band Feed Array (ALFA) at
Arecibo. Over the next few years, it will cover fields in a wide
variety of environments, ranging from the Local Void through isolated
galaxies, galaxy pairs and galaxy groups to the Virgo Cluster, with
higher sensitivity, higher velocity resolution and higher spatial
resolution than previous HI surveys. This will enable the environmental
dependance of the HI Mass Function (HIMF) to be determined and will
also allow low HI-mass, and high HI-mass to light ratio objects to
be discovered. Here we present an overview of the survey and initial
results from the first survey field, observed in January 2006.The
Arecibo Observatory is part of the National Astronomy and Ionosphere
Center, which is operated by Cornell University under a cooperative
agreement with the National Science Foundation
---------------------------------------------------------
Title: Axisymmetric simulations of magneto-rotational core collapse:
dynamics and gravitational wave signal
Authors: Obergaulinger, M.; Aloy, M. A.; Müller, E.
2006A&A...450.1107O Altcode: 2005astro.ph.10184O
Aims.We have performed a comprehensive parameter study of
the collapse of rotating, strongly magnetized stellar cores
in axisymmetry to determine their gravitational wave signature
based on the Einstein quadrupole formula. <BR /> Methods: .We use
a Newtonian explicit magnetohydrodynamic Eulerian code based on the
relaxing-TVD method for the solution of the ideal MHD equations, and
apply the constraint-transport method to guarantee a divergence-free
evolution of the magnetic field. We neglect effects due to neutrino
transport and employ a simplified equation of state. The initial
models are polytropes in rotational equilibrium with a prescribed
degree of differential rotation and rotational energy. The initial
magnetic fields are purely poloidal the field strength ranging from
10<SUP>10</SUP>~G to 10<SUP>13</SUP>~G. The evolution of the core is
followed until a few ten milliseconds past core bounce. <BR /> Results:
.The initial magnetic fields are amplified mainly by the differential
rotation of the core giving rise to a strong toroidal field component
with an energy comparable to the rotational energy. The poloidal field
component grows by compression during collapse, but does not change
significantly after core bounce. In large parts of the simulated
cores the growth time of the magneto-rotational instability (MRI)
is of the order of a few milliseconds. The saturation field strengths
that can be reached both via a pure Ω dynamo or the MRI are of the
order of 10<SUP>15</SUP>~G at the surface of the core. Sheet-like
circulation flows which produce a strong poloidal field component
transporting angular momentum outwards develop due to MRI, provided
the initial field is not too weak. Weak initial magnetic fields
(⪉10<SUP>11</SUP>~G) have no significant effect on the dynamics
of the core and the gravitational wave signal. Strong initial
fields (⪆10<SUP>12</SUP>~G) cause considerable angular momentum
transport whereby rotational energy is extracted from the collapsed
core which loses centrifugal support and enters a phase of secular
contraction. The gravitational wave amplitude at bounce changes by up to
a few ten percent compared to the corresponding non-magnetic model. If
the angular momentum losses are large, the post-bounce model. If the
angular momentum losses are large the post-bounce equilibrium state of
the core changes from a centrifugally to a pressure supported one. This
transition imprints in the gravitational wave signal a reduction of
the amplitude of the large-scale oscillations characteristic of cores
bouncing due to centrifugal forces. In some models the quasi-periodic
large-scale oscillations are replaced by higher frequency irregular
oscillations. This pattern defines a new signal type which we call a
type IV gravitational wave signal. Collimated bipolar outflows give
rise to a unique feature that may allow their detection by means
of gravitational wave astronomy: a large positive quadrupole wave
amplitude of similar size as that of the bounce signal.<BR />
---------------------------------------------------------
Title: Exploring the relativistic regime with Newtonian hydrodynamics:
an improved effective gravitational potential for supernova
simulations
Authors: Marek, A.; Dimmelmeier, H.; Janka, H. -Th.; Müller, E.;
Buras, R.
2006A&A...445..273M Altcode: 2005astro.ph..2161M
We investigate the possibility approximating relativistic effects in
hydrodynamical simulations of stellar core collapse and post-bounce
evolution by using a modified gravitational potential in an otherwise
standard Newtonian hydrodynamic code. Different modifications
of a previously introduced effective relativistic potential are
discussed. Corresponding hydrostatic solutions are compared with
solutions of the TOV equations, and hydrodynamic simulations with two
different codes are compared with fully relativistic results. One
code is applied for one- and two-dimensional calculations with a
simple equation of state, and employs either the modified effective
relativistic potential in a Newtonian framework or solves the general
relativistic field equations under the assumption of the conformal
flatness condition (CFC) for the three-metric. The second code allows
for full-scale supernova runs including a microphysical equation of
state and neutrino transport based on the solution of the Boltzmann
equation and its moments equations. We present prescriptions for the
effective relativistic potential for self-gravitating fluids to be
used in Newtonian codes, which produce excellent agreement with fully
relativistic solutions in spherical symmetry, leading to significant
improvements compared to previously published approximations. Moreover,
they also approximate qualitatively well relativistic solutions for
models with rotation.
---------------------------------------------------------
Title: How to blow up a star.
Authors: Hillebrandt, W.; Janka, H. -T.; Mueller, E.
2006SciAm.295d..42H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: ARPS: an Advanced Radio Isotope Power Subsystem for ExoMars
Geophysical Package (GEP)
Authors: Mimoun, D.; Biele, J.; Lenoir, B.; Dauscher, A.; Müller, E.
2005AGUFM.P51C0935M Altcode:
Within the framework of the ESA Aurora initiative , IPGP, DLR and
an international consortium of laboratories launched an initiative
aiming at adding on board the ExoMars mission a long life geophysical
observatory, called "GEP" (Geophysical package) or "Mars Long Lived
Surface Package". The feasibility study of this "geophysical package",
carried out with the CNES support, showed the need for studying an
alternative source of power to solar panels. Developments related to RTG
technologies have been restricted for a long time to the United States
and Russian industries. However, the exploration of the remote solar
system (in the frame of the ESA Cosmic Vision) as well as long duration
planetary missions (such as ExoMars Geophysical Package GEP ) exclude de
facto the use of solar panels. A possible solution would be to associate
to a radioisotope heat source of Russian origin (of Angel type) a
thermo-electrical conversion system of European design. A European
consortium of laboratories, including LPM, IPG and DLR (WF and RS)
was thus constituted, in order to validate by a study the assumptions
on the electric subsystem for the preliminary sizing of the geophysical
package. The power of this Advanced radio-isotopic power system (ARPS)
should be between 3 and 4 W, and the proposed mass limited to about
3 to 4 kg. This study will be undertaken in collaboration between the
LPM, IPGP, DLR-WF and DLR-RS. A preliminary iteration of the GEP power
subsystem will be presented, and main trade-off will be considered.
---------------------------------------------------------
Title: Ca II K observations of QSOs in the line-of-sight to the
Magellanic Bridge
Authors: Smoker, J. V.; Keenan, F. P.; Thompson, H. M. A.; Brüns,
C.; Muller, E.; Lehner, N.; Lee, J. -K.; Hunter, I.
2005A&A...443..525S Altcode: 2005astro.ph.10507S
We describe medium-resolution spectroscopic observations taken
with the ESO Multi-Mode Instrument (emmi) in the Ca ii K line
(λ_air=3933.661 Å) towards 7 QSOs located in the line-of-sight
to the Magellanic Bridge. At a spectral resolution R = λ/Δλ =
6000, five of the sightlines have a signal-to-noise (S/N) ratio
of 20 or higher. Definite Ca absorption due to Bridge material is
detected towards 3 objects, with probable detection towards two
other sightlines. Gas-phase Ca ii K Bridge and Milky Way abundances
or lower limits for the all sightlines are estimated by the use of
Parkes 21-cm H i emission line data. These data only have a spatial
resolution of 14 arcmin compared with the optical observations which
have milli-arcsecond resolution. With this caveat, for the three objects
with sound Ca ii K detections, we find that the ionic abundance of Ca
ii K relative to H i, A=log(N(Ca K)/N(H i)) for low-velocity Galactic
gas ranges from -8.3 to -8.8 dex, with H i column densities varying
from 3-6×10<SUP>20</SUP> cm<SUP>-2</SUP>. For Magellanic Bridge gas,
the values of A are 0.5 dex higher, ranging from -7.8 to -8.2 dex,
with N(H i) = 1{-}5×10<SUP>20</SUP> cm<SUP>-2</SUP>. Higher values
of A correspond to lower values of N(H i), although numbers are
small. For the sightline towards B 0251-675, the Bridge gas has two
different velocities, and in only one of these is Ca ii tentatively
detected, perhaps indicating gas of a different origin or present-day
characteristics (such as dust content), although this conclusion is
uncertain and there is the possibility that one of the components could
be related to the Magellanic Stream. Higher signal-to-noise Ca ii K
data and higher resolution H i data are required to determine whether
A changes with N(H i) over the Bridge and if the implied difference in
the metalicity of the two Bridge components towards B 0251-675 is real.
---------------------------------------------------------
Title: Which physical parameters can be inferred from the emission
variability of relativistic jets?
Authors: Mimica, P.; Aloy, M. A.; Müller, E.; Brinkmann, W.
2005A&A...441..103M Altcode: 2005astro.ph..6636M
We present results of a detailed numerical study and theoretical
analysis of the dynamics of internal shocks in relativistic jets and the
non-thermal flares associated with these shocks. In our model internal
shocks result from collisions of density inhomogeneities (shells) in
relativistic jet flows. We find that the merged shell resulting from
the inelastic collision of shells has a complicated internal structure
due to the non-linear dynamics of the interaction. Furthermore, the
instantaneous efficiency for converting kinetic energy into thermal
energy is found to be almost twice as high as theoretically expected
during the period of significant emission. The Lorentz factors of
the internal shocks are correlated with the initial inertial masses
of the shells. Because of the complexity of the non-linear evolution
the merged shell becomes very inhomogeneous and simple one-zone models
are inadequate to extract physical parameters of the emitting region
from the resulting light curves. In order to improve on these one-zone
approximations, we propose a novel way of analyzing the space-time
properties of the emission. Based on these properties we construct an
analytic model of non-thermal flares which can be used to constrain some
(unobservable) physical parameters of the internal shocks. These are
the ratio of the Lorentz factors between the forward and the reverse
shock (caused by the shell collision), and the shell crossing times
of these shocks. The analytic model is validated by applying it to
the synthetic light curves computed from our models. It can equally
well be applied to observations.
---------------------------------------------------------
Title: Supernova Asymmetries and Pulsar Kicks --- Views on
Controversial Issues
Authors: Janka, H. -Th.; Scheck, L.; Kifonidis, K.; Müller, E.;
Plewa, T.
2005ASPC..332..363J Altcode: 2004astro.ph..8439J; 2005ASPC..332..372J
Two- and three-dimensional simulations demonstrate that hydrodynamic
instabilities can lead to low-mode (l=1, 2) asymmetries of the fluid
flow in the neutrino-heated layer behind the supernova shock. This
provides a natural explanation for aspherical mass ejection and for
pulsar recoil velocities even in excess of 1000 km/s. We propose
that the bimodality of the pulsar velocity distribution might be a
consequence of a dominant l=1 mode in case of the fast component,
while higher-mode anisotropy characterizes the postshock flow and
SN ejecta during the birth of the slow neutron stars. We argue that
the observed large asymmetries of supernovae and the measured high
velocities of young pulsars therefore do not imply rapid rotation
of the iron core of the progenitor star, nor do they require strong
magnetic fields to play a crucial role in the explosion. Anisotropic
neutrino emission from accretion contributes to the neutron star
acceleration on a minor level, and pulsar kicks do not make a good
case for non-standard neutrino physics in the nascent neutron star.
---------------------------------------------------------
Title: CFC+: improved dynamics and gravitational waveforms from
relativistic core collapse simulations
Authors: Cerdá-Durán, P.; Faye, G.; Dimmelmeier, H.; Font, J. A.;
Ibáñez, J. M.; Müller, E.; Schäfer, G.
2005A&A...439.1033C Altcode: 2004astro.ph.12611C
Core collapse supernovae are a promising source of detectable
gravitational waves. Most of the existing (multidimensional) numerical
simulations of core collapse in general relativity were done using
approximations of the Einstein field equations. As recently shown
by Dimmelmeier et al. (2002a, A&A, 388, 917), Dimmelmeier et
al. (2002b, A&A, 393, 523), one of the most interesting such
approximations is the so-called conformal flatness condition (CFC)
of Isenberg, Wilson; and Mathews. Building on this previous work
we present new results from numerical simulations of relativistic
rotational core collapse in axisymmetry, with the aim of improving
the dynamics and gravitational waveforms. The computer code used for
these simulations models the evolution of the coupled system of metric
and fluid equations using the 3 + 1 formalism, specialized to a new
framework for the gravitational field equations we call CFC+. In this
approach we add new degrees of freedom to the original CFC equations,
which extend them by terms of second post-Newtonian order. The
resulting metric equations are still of elliptic type, but the number
of equations is significantly augmented in comparison to the original
CFC approach. The hydrodynamic evolution and the CFC spacetime metric
are calculated with the code developed by Dimmelmeier et al.(2002a,
A&A, 388, 917), which has been conveniently extended to account
for the additional CFC+ equations. The corrections included in CFC+
are computed by solving a system of elliptic linear equations. The new
formalism is assessed with time evolutions of both rotating neutron
stars in equilibrium and gravitational core collapse of rotating
polytropes. Gravitational wave signals for a comprehensive sample
of collapse models are extracted using either the quadrupole formula
or directly from the metric. We discuss our results on the dynamics
and the gravitational wave emission through a detailed comparison
between CFC and CFC+ simulations. The main conclusion is that, for the
neutron star spacetimes analyzed in the present work, no significant
differences are found among CFC, CFC+, and full general relativity,
which highlights the suitability of the former.
---------------------------------------------------------
Title: Relativistic outflows from remnants of compact object mergers
and their viability for short gamma-ray bursts
Authors: Aloy, M. A.; Janka, H. -T.; Müller, E.
2005A&A...436..273A Altcode: 2004astro.ph..8291A
We present the first general relativistic hydrodynamic models of the
launch and evolution of relativistic jets and winds, driven by thermal
energy deposition, possibly due to neutrino-antineutrino annihilation,
in the close vicinity of black hole-accretion torus systems. The latter
are considered to be the remnants of compact object mergers. Our
two-dimensional simulations establish the link between models of
such mergers and future observations of short gamma-ray bursts by
the SWIFT satellite. They show that ultrarelativistic outflow with
maximum terminal Lorentz factors around 1000 develops for polar energy
deposition rates above some 10<SUP>48</SUP> erg s<SUP>-1</SUP> per
steradian, provided the merger environment has a sufficiently low
baryon density. By the interaction with the dense accretion torus
the ultrarelativistic outflow with Lorentz factors Γ above 100 is
collimated into a sharp-edged cone that is embedded laterally by a wind
with steeply declining Lorentz factor. The typical semi-opening angles
of the Γ > 100 cone are 5°-10°, corresponding to about 0.4-1.5% of
the hemisphere and apparent isotropized energies (kinetic plus internal)
up to ≈10<SUP>51</SUP> erg although at most 10-30% of the deposited
energy is transferred to the outflow with Γ > 100. The viability of
post-merger black hole-torus systems as engines of short, hard gamma-ray
bursts is therefore confirmed. The annihilation of neutrino-antineutrino
pairs radiated from the hot accretion torus appears as a suitable energy
source for powerful axial outflow even if only ≈10<SUP>49</SUP> erg
are deposited within a cone of 45° half-opening angle around the system
axis. Although the torus lifetimes are expected to be only between
some 0.01 s and several 0.1 s, our models can explain the durations
of all observed short gamma-ray bursts, because different propagation
velocities of the front and rear ends will lead to a radial stretching
of the ultrarelativistic fireball before transparency is reached. The
ultrarelativistic flow reveals a highly non-uniform structure caused
by the action of Kelvin-Helmholtz instabilities that originate at the
fireball-torus interface. Large radial variations of the baryon density
(up to several orders of magnitude) are uncorrelated with moderate
variations of the Lorentz factor (factors of a few) and fluctuations
of the gently declining radiation-dominated pressure. In the angular
direction the Lorentz factor reveals a nearly flat plateau-like maximum
with values of several hundreds, that can be located up to 7° off the
symmetry axis, and a steep decrease to less than 10 for polar angles
larger than 15°-20°. Lateral expansion of the ultrarelativistic core
of the flow is prevented by a subsonic velocity component of about
0.05c towards the symmetry axis, whereas the moderately relativistic
wings show a subsonic sideways inflation with less than 0.07c (measured
in the frame comoving with the radial flow).
---------------------------------------------------------
Title: Relativistic MHD simulations of extragalactic jets
Authors: Leismann, T.; Antón, L.; Aloy, M. A.; Müller, E.; Martí,
J. M.; Miralles, J. A.; Ibáñez, J. M.
2005A&A...436..503L Altcode:
We have performed a comprehensive parameter study of the morphology
and dynamics of axisymmetric, magnetized, relativistic jets by means
of numerical simulations. The simulations have been performed with an
upgraded version of the GENESIS code which is based on a second-order
accurate finite volume method involving an approximate Riemann solver
suitable for relativistic ideal magnetohydrodynamic flows, and a
method of lines. Starting from pure hydrodynamic models we consider
the effect of a magnetic field of increasing strength (up to β ≡
|b|<SUP>2</SUP>/2p ≈ 3.3 times the equipartition value) and different
topology (purely toroidal or poloidal). We computed several series of
models investigating the dependence of the dynamics on the magnetic
field in jets of different beam Lorentz factor and adiabatic index. We
find that the inclusion of the magnetic field leads to diverse effects
which contrary to Newtonian magnetohydrodynamics models do not always
scale linearly with the (relative) strength of the magnetic field. The
relativistic models show, however, some clear trends. Axisymmetric
jets with toroidal magnetic fields produce a cavity which consists of
two parts: an inner one surrounding the beam which is compressed by
magnetic forces, and an adjacent outer part which is inflated due to
the action of the magnetic field. The outer border of the outer part
of the cavity is given by the bow-shock where its interaction with
the external medium takes place. Toroidal magnetic fields well below
equipartition (β = 0.05) combined with a value of the adiabatic index
of 4/3 yield extremely smooth jet cavities and stable beams. Prominent
nose cones form when jets are confined by toroidal fields and carry a
high Poynting flux (σ≡ |b|<SUP>2</SUP>/ρ>0.01 and β≥ 1). In
contrast, none of our models possessing a poloidal field develops
such a nose cone. The size of the nose cone is correlated with the
propagation speed of the Mach disc (the smaller the speed the larger
is the size). If two models differ only by the adiabatic index, jets
having smaller adiabatic indices tend to develop smaller nose cones.
---------------------------------------------------------
Title: Producing short GRBs from coalescing compact binaries
Authors: Aloy, M. A.; Janka, H. -Th.; Müller, E.
2005NCimC..28..399A Altcode:
We present some of the results of a series of relativistic hydrodynamic
simulations of compact binary mergers as potential candidates to be
progenitors of short gamma-ray bursts. We discuss some of the generic
conditions under which a short gamma-ray burst can be initiated in
this kind of progenitor and the main characteristics of the resulting
outflow.
---------------------------------------------------------
Title: The Parkes H I Survey of the Magellanic System
Authors: Brüns, C.; Kerp, J.; Staveley-Smith, L.; Mebold, U.; Putman,
M. E.; Haynes, R. F.; Kalberla, P. M. W.; Muller, E.; Filipovic, M. D.
2005A&A...432...45B Altcode: 2004astro.ph.11453B
We present the first fully and uniformly sampled, spatially complete
HI survey of the entire Magellanic System with high velocity
resolution (Δ v = 1.0 km s<SUP>-1</SUP>), performed with the
Parkes Telescope. Approximately 24 percent of the southern sky was
covered by this survey on a ≈5´ grid with an angular resolution
of HPBW = 14.1 arcmin. A fully automated data-reduction scheme was
developed for this survey to handle the large number of HI spectra
(1.5×10<SUP>6</SUP>). The individual Hanning smoothed and polarization
averaged spectra have an rms brightness temperature noise of σ =
0.12 K. The final data-cubes have an rms noise of σ<SUB>rms</SUB>
≈ 0.05 K and an effective angular resolution of ≈16´. In
this paper we describe the survey parameters, the data-reduction
and the general distribution of the HI gas. The Large Magellanic
Cloud (<ASTROBJ>LMC</ASTROBJ>) and the Small Magellanic Cloud
(<ASTROBJ>SMC</ASTROBJ>) are associated with huge gaseous features -
the <ASTROBJ>Magellanic Bridge</ASTROBJ>, the <ASTROBJ>Interface
Region</ASTROBJ>, the <ASTROBJ>Magellanic Stream</ASTROBJ>, and
the <ASTROBJ>Leading Arm</ASTROBJ> - with a total HI mass of M(HI) =
4.87×10<SUP>8</SUP> M<SUB>⊙</SUB> [d/55 kpc]<SUP>2</SUP>, if all HI
gas is at the same distance of 55 kpc. Approximately two thirds of this
HI gas is located close to the Magellanic Clouds (<ASTROBJ>Magellanic
Bridge</ASTROBJ> and <ASTROBJ>Interface Region</ASTROBJ>), and
25% of the HI gas is associated with the <ASTROBJ>Magellanic
Stream</ASTROBJ>. The <ASTROBJ>Leading Arm</ASTROBJ> has a four
times lower HI mass than the <ASTROBJ>Magellanic Stream</ASTROBJ>,
corresponding to 6% of the total HI mass of the gaseous features. We
have analyzed the velocity field of the Magellanic Clouds and their
neighborhood introducing a LMC-standard-of-rest frame. The HI in the
<ASTROBJ>Magellanic Bridge</ASTROBJ> shows low velocities relative
to the Magellanic Clouds suggesting an almost parallel motion, while
the gas in the <ASTROBJ>Interface Region</ASTROBJ> has significantly
higher relative velocities indicating that this gas is leaving
the <ASTROBJ>Magellanic Bridge</ASTROBJ> building up a new section
of the <ASTROBJ>Magellanic Stream</ASTROBJ>. The <ASTROBJ>Leading
Arm</ASTROBJ> is connected to the <ASTROBJ>Magellanic Bridge</ASTROBJ>
close to an extended arm of the <ASTROBJ>LMC</ASTROBJ>. The clouds
in the <ASTROBJ>Magellanic Stream</ASTROBJ> and the <ASTROBJ>Leading
Arm</ASTROBJ> show significant differences, both in the column density
distribution and in the shapes of the line profiles. The HI gas in
the <ASTROBJ>Magellanic Stream</ASTROBJ> is more smoothly distributed
than the gas in the <ASTROBJ>Leading Arm</ASTROBJ>. These morphological
differences can be explained if the <ASTROBJ>Leading Arm</ASTROBJ> is at
considerably lower z-heights and embedded in a higher pressure ambient
medium. <P />The Parkes Telescope is part of the Australia Telescope
which is funded by the Commonwealth of Australia for operation as a
National Facility managed by CSIRO.
---------------------------------------------------------
Title: Relativistic Outflows From Remnants of Compact Object Mergers
and Their Viability as Progenitors of Short Gamma-ray Bursts
Authors: Aloy, M. A.; Janka, T. -H.; Müller, E.
2005tsra.conf...69A Altcode:
We summarize the most important results of a series of relativistic
hydrodynamic simulations of mergers of compact binaries as potential
candidates to be progenitors of short gamma-ray bursts. We discuss
some of the generic conditions under which a short gamma-ray burst can
be initiated and collimated in this kind of progenitor and the main
characteristics of the resulting outflow. We conclude that not every
merger will be able to produce a short gamma-ray burst. The generation
of a successful event depends on the mass of the halo produced during
the process of merging of the system. Due to the lateral structure
of the generated ultrarelativistic outflows we expect some degree of
variability between observed bursts, depending on the viewing angle
relative to the system axis. Such differences will be superimposed
on variations due to intrinsic properties of the binary systems and
remnant BH-torus systems, e.g., associated with different masses and
spins of the merging neutron stars or black holes.
---------------------------------------------------------
Title: Nucleosynthesis in Multi-Dimensional Simulations of SNII
Authors: Travaglio, C.; Kifonidis, K.; Müller, E.
2005coex.conf..297T Altcode: 2005IAUCo.192..297T
We investigate explosive nuclear burning in core collapse supernovae by
coupling a tracer particle method to one- and two-dimensional Eulerian
hydrodynamic calculations. Adopting the most recent experimental and
theoretical nuclear data, we compute the nucleosynthetic yields for
15 M<SUB>⨀</SUB> stars with solar metallicity, by post-processing
the temperature and density history of advected tracer particles. We
compare our results to 1D calculations published in the literature.
---------------------------------------------------------
Title: HI Observations of High Velocity Clouds
Authors: Saucedo-McQuade, K.; Pantoja, C.; Lebron, M.; Muller, E.
2004AAS...20514214S Altcode: 2004BAAS...36.1583S
We present the reduced data of selected observations of High Velocity
Clouds (HVCs). The data were from previous observations of HVCs made
at Arecibo Observatory using L and C band receivers. <P />For this
project, a sample of HVCs was selected from the HI survey by Hartmann
and Burton (1997). These HVCs were selected so that they have a strong
continuum source near their position. The data was studied for three
sources from this survey. These sources were observed using a cross
pattern with 12 minutes ON source and 12 minutes OFF source. The OFFs
were taken at positions 1 beamwidth away (NS EW) from the continuum
source position. The associated absorption line spectra was reduced
using available IDL routines and the column densities for HI and
formaldehyde data were calculated. <P />This research was part of
the Research Experiences for Undergraduates (REU) Program at Arecibo
Observatory. The REU Program is sponsored by the National Science
Foundation. Arecibo Observatory is operated by NAIC, Cornell University,
under a cooperative agreement with the NSF.
---------------------------------------------------------
Title: Relativistic outflows from remnants of compact ob ject mergers
and their viability for short gamma-ray bursts
Authors: Aloy, M. A.; Janka, H. -Th; Müller, E.
2004txra.confE...1A Altcode:
We summarize the most important results of a series of relativistic
hydrodynamic simulations of mergers of compact binaries as potential
candidates to be progenitors of short gamma-ray bursts. We discuss
some of the generic conditions under which a short gamma-ray burst can
be initiated and collimated in this kind of progenitor and the main
characteristics of the resulting outflow. We conclude that not every
merger will be able to produce a short gamma-ray burst. The generation
of a successful event depends on the mass of the halo produced during
the process of merging of the system. Due to the lateral structure
of the generated ultrarelativistic outflows we expect some degree of
variability between observed bursts, depending on the viewing angle
relative to the system axis. Such differences will be superimposed
on variations due to intrinsic properties of the binary systems and
remnant BH-torus systems, e.g., associated with different masses and
spins of the merging neutron stars or black holes.
---------------------------------------------------------
Title: A Statistical Investigation of H I in the Magellanic Bridge
Authors: Muller, E.; Stanimirović, S.; Rosolowsky, E.; Staveley-Smith,
L.
2004ApJ...616..845M Altcode: 2004astro.ph..8259M
We present results from two statistical analyses applied to a neutral
hydrogen (H I) data set of the nearby tidal bridge in the Magellanic
System. Primarily, analyses of the spatial power spectrum suggest
that the Magellanic Bridge, historically considered to be a single
contiguous feature, may in fact be a projection of two kinematically and
morphologically distinct structures. The southern and more obviously
turbulent parts appear to show structure organized similarly to the
adjacent Small Magellanic Cloud (SMC), while the northern regions are
shown to be relatively deficient in large-scale power. The extent of
modification to the spatial power index by the velocity fluctuations
is also highly variant across these parts of the Bridge. We find again
that the northern part appears distinct from the southern part and from
the SMC, in that the power spectrum is significantly more affected
by slower velocity perturbations. We also probe the rate of spectral
variation of the H I by measuring the spectral correlation function over
selected regions. The results from this analysis highlight a tendency
for the H I spectra within the bright parts of the Bridge to have a
more persistent correlation in the east-west direction than in the
north-south direction. These results are considered to be quantitative
evidence for the tidal processes that are thought to have been active
throughout the evolution of the Magellanic Bridge.
---------------------------------------------------------
Title: A Sensitive Study of Absorption by Neutral Hydrogen and
Molecular Material in Intermediate and High Velocity clouds.
Authors: Pantoja, C.; Lebron, M.; Muller, E.
2004AAS...20514215P Altcode: 2004BAAS...36R1583P
We have conducted a sensitive study of the molecular and HI components
in gas associated with selected high and intermediate velocity
clouds. The Arecibo Telescope was used to measure absorption of
bright continuum sources at the HI and H<SUB>2</SUB>CO transitions,
as well as to map the HI emission of a number of selected clouds. No
molecular material was detected in any of the targets, to an rms of ∼8
mK. Absorption by HVCs is uncommon and we show here two HI absorption
measurements which were a product of this survey. We find that gas which
can be convincingly associated with HVCs shows evidence for a warm and
cool component, whereas the high velocity gas found in the periphery
of the clouds is generally warm, thermally homogenous and unenriched.
---------------------------------------------------------
Title: The First Steps in the Life of a Short GRB
Authors: Aloy, M. -A.; Janka, H. -T.; Müller, E.
2004AIPC..727..380A Altcode:
We present some results of relativistic hydrodynamic simulations
of post-neutron star merger disks as potential candidates to be
progenitors of short gamma-ray bursts. We discuss some of the generic
conditions under which a gamma-ray burst can be initiated in this kind
of progenitor and the characteristics of the resulting outflow.
---------------------------------------------------------
Title: Study of H I and Star Formation Sites in the Magellanic Bridge
Authors: Muller, E.; Staveley-Smith, L.; Zealey, W.
2004IAUS..217..506M Altcode:
Tidal features represent an important process for the recycling of
matter across extremely large spatial scales. The Magellanic Bridge
is the closest gaseous tidal feature to our own Galaxy, and offers an
ideal opportunity to study the active processes in such phenomena at
high spatial resolutions otherwise unavailable. The neutral hydrogen of
the western Magellanic Bridge, has been observed with both the Parkes
64m telescope and ATCA interferometer and the resulting dataset has
revealed an extremely complex and chaotic morphology. We discuss these
observations here with reference to a variety of analyses: the spatial
correlation of apparently expanding HI shells with OB associations
and the outcome of sensitive Hα and CO surveys.
---------------------------------------------------------
Title: Global Anisotropies in Supernova Explosions and Pulsar Recoil
Authors: Scheck, L.; Plewa, T.; Kifonidis, K.; Janka, H. -Th.;
Müller, E.
2004astro.ph..5311S Altcode:
We show by two-dimensional and first three-dimensional simulations
of neutrino-driven supernova explosions that low (l=1,2) modes can
dominate the flow pattern in the convective postshock region on
timescales of hundreds of milliseconds after core bounce. This can
lead to large global anisotropy of the supernova explosion and pulsar
kicks in excess of 500 km/s.
---------------------------------------------------------
Title: Synthetic X-ray light curves of BL Lacs from relativistic
hydrodynamic simulations
Authors: Mimica, P.; Aloy, M. A.; Müller, E.; Brinkmann, W.
2004A&A...418..947M Altcode: 2004astro.ph..1266M
We present the results of relativistic hydrodynamic simulations of the
collision of two dense shells in a uniform external medium, as envisaged
in the internal shock model for BL Lac jets. The non-thermal radiation
produced by highly energetic electrons injected at the relativistic
shocks is computed following their temporal and spatial evolution. The
acceleration of electrons at the relativistic shocks is parametrized
using two different models and the corresponding X-ray light curves are
computed. We find that the interaction time scale of the two shells
is influenced by an interaction with the external medium. For the
chosen parameter sets, the efficiency of the collision in converting
dissipated kinetic energy into the observed X-ray radiation is of the
order of one percent.
---------------------------------------------------------
Title: Nucleosynthesis in multi-dimensional simulations of SNII
Authors: Travaglio, C.; Kifonidis, K.; Müller, E.
2004NewAR..48...25T Altcode:
We investigate explosive nuclear burning in core collapse supernovae by
coupling a tracer particle method to one- and two-dimensional Eulerian
hydrodynamic calculations. Adopting the most recent experimental and
theoretical nuclear data, we compute the nucleosynthetic yields for 15
M<SUB>⊙</SUB> stars with solar metallicity, by post-processing the
temperature and density history of advected tracer particles. We compare
our results to one-dimensional calculations published in the literature.
---------------------------------------------------------
Title: Pulsar Recoil by Large-Scale Anisotropies in Supernova
Explosions
Authors: Scheck, L.; Plewa, T.; Janka, H. -Th.; Kifonidis, K.;
Müller, E.
2004PhRvL..92a1103S Altcode: 2003astro.ph..7352S
Assuming that the neutrino luminosity from the neutron star core is
sufficiently high to drive supernova explosions by the neutrino-heating
mechanism, we show that low-mode (l=1,2) convection can develop
from random seed perturbations behind the shock. A slow onset of the
explosion is crucial, requiring the core luminosity to vary slowly
with time, in contrast to the burstlike exponential decay assumed in
previous work. Gravitational and hydrodynamic forces by the globally
asymmetric supernova ejecta were found to accelerate the remnant neutron
star on a time scale of more than a second to velocities above 500 km
s<SUP>-1</SUP>, in agreement with observed pulsar proper motions.
---------------------------------------------------------
Title: Multi-dimensional Nucleosynthesis Calculations of Type II SNe
Authors: Travaglio, C.; Kifonidis, K.; Müller, E.
2004oee..sympE..56T Altcode: 2003astro.ph..5440T
We investigate explosive nuclear burning in core collapse supernovae by
coupling a tracer particle method to one and two-dimensional Eulerian
hydrodynamic calculations. Adopting the most recent experimental and
theoretical nuclear data, we compute the nucleosynthetic yields for
15 M<SUB>odot</SUB> stars with solar metallicity, by post-processing
the temperature and density history of advected tracer particles. We
compare our results to 1D calculations published in the literature.
---------------------------------------------------------
Title: A Statistical investigation of HI in the Magellanic Bridge
Authors: Muller, E.; Stanimirović, S.; Rosolowsky, E.; Staveley-Smith,
L.
2003AAS...20310504M Altcode: 2003BAAS...35.1374M
We present results from two statistical structural analyses of the
nearby tidal HI Bridge in the Magellanic system. Analyses of the
spatial power spectrum suggest that the Magellanic Bridge, historically
considered to be a single coherent feature, may in fact be a projection
of two kinematically and morphologically distinct structures, possibly
representing two arms of the Small Magellanic Cloud (SMC). The more
turbulent southern parts of the Bridge appear to show structure
organised similarly to the adjacent SMC, while the northern regions
are shown to be relatively deficient in a large scale power. The
modifications to the spatial power index by velocity fluctuations
and the turbulent component are also highly variant across these two
regions, where the northern part is significantly more affected by
slower velocity perturbations than is the southern part. <P />We also
probe the rate of variation of the HI spectra throughout the Bridge, by
measuring the Spectral Correlation over selected subsets. The Spectral
correlation algorithm is shown to be more sensitive to low-power
structural variations than is the Fourier transformations used for the
spatial power spectrum, and the results from this analysis highlight
a tendency for the spectra of bright parts of the HI in the Bridge
to have a more persistent correlation along a direction towards the
Large Magellanic Cloud (LMC) and SMC. We attbribute this arrangement
of structure to the large-scale tidal processes active during the
evolution of the Magellanic Bridge.
---------------------------------------------------------
Title: Non-spherical core collapse supernovae. I. Neutrino-driven
convection, Rayleigh-Taylor instabilities, and the formation and
propagation of metal clumps
Authors: Kifonidis, K.; Plewa, T.; Janka, H. -Th.; Müller, E.
2003A&A...408..621K Altcode: 2003astro.ph..2239K
We have performed two-dimensional simulations of core collapse
supernovae that encompass shock revival by neutrino heating,
neutrino-driven convection, explosive nucleosynthesis, the growth of
Rayleigh-Taylor instabilities, and the propagation of newly formed
metal clumps through the exploding star. A simulation of a type
II explosion in a 15 M<SUB>sun</SUB> blue supergiant progenitor is
presented, that confirms our earlier type II models and extends their
validity to times as late as 5.5 hours after core bounce. We also study
a type Ib-like explosion, by simply removing the hydrogen envelope of
the progenitor model. This allows for a first comparison of type II
and type Ib evolution. We present evidence that the hydrodynamics of
core collapse supernovae beyond shock revival differs markedly from
the results of simulations that have followed the Rayleigh-Taylor
mixing starting from ad hoc energy deposition schemes to initiate
the explosion. We find iron group elements to be synthesized in an
anisotropic, dense, low-entropy shell that expands with velocities
of ~ 17 000 km s<SUP>-1</SUP> shortly after shock revival. The growth
of Rayleigh-Taylor instabilities at the Si/O and (C+O)/He composition
interfaces of the progenitor, seeded by the flow-structures resulting
from neutrino-driven convection, leads to a fragmentation of this shell
into metal-rich “clumps”. This fragmentation starts already ~ 20 s
after core bounce and is complete within the first few minutes of the
explosion. During this time the clumps are slowed down by drag, and by
the positive pressure gradient in the unstable layers. However, at t ~
300 s they decouple from the flow and start to propagate ballistically
and subsonically through the He core, with the maximum velocities
of metals remaining constant at ~ 3500 - 5500 km s<SUP>-1</SUP>. This
early “clump decoupling” leads to significantly higher <SUP>56</SUP>Ni
velocities at t = 300 s than in one-dimensional models of the explosion,
demonstrating that multi-dimensional effects which are at work within
the first minutes, and which have been neglected in previous studies
(especially in those which dealt with the mixing in type II supernovae),
are crucial. Despite comparably high initial maximum nickel velocities
in both our type II and our type Ib-like model, we find that there
are large differences in the final maximum nickel velocities between
both cases. In the “type Ib” model the maximum velocities of metals
remain frozen in at ~ 3500 - 5500 km s<SUP>-1</SUP> for t >= 300
s, while in the type II model they drop significantly for t >
1500 s. In the latter case, the massive hydrogen envelope of the
progenitor forces the supernova shock to slow down strongly, leaving
behind a reverse shock and a dense helium shell (or “wall”) below
the He/H interface. After penetrating into this dense material the
metal-rich clumps possess supersonic speeds, before they are slowed
down by drag forces to ~ 1200 km s<SUP>-1</SUP> at a time of 20 000 s
post-bounce. While, due to this deceleration, the maximum velocities
of iron-group elements in SN 1987 A cannot be reproduced in case of
the considered 15 M<SUB>sun</SUB> progenitor, the “type Ib” model is
in fairly good agreement with observed clump velocities and the amount
of mixing inferred for type Ib supernovae. Thus it appears promising
for calculations of synthetic spectra and light curves. Furthermore,
our simulations indicate that for type Ib explosions the pattern of
clump formation in the ejecta is correlated with the structure of the
convective pattern prevailing during the shock-revival phase. This
might be used to deduce observational constraints for the dynamics
during this early phase of the evolution, and the role of neutrino
heating in initiating the explosion.
---------------------------------------------------------
Title: A search for 85.5- and 86.6-GHz methanol maser emission
Authors: Ellingsen, S. P.; Cragg, D. M.; Minier, V.; Muller, E.;
Godfrey, P. D.
2003MNRAS.344...73E Altcode: 2003astro.ph..5236E
We have used the Australia Telescope National Facility Mopra
22-m millimetre telescope to search for emission from the 85.5-GHz
6<SUB>-2</SUB>-7<SUB>-1</SUB> E and 86.6-GHz 7<SUB>2</SUB>-6<SUB>3</SUB>
A<SUP>-</SUP> transitions of methanol. The search was targeted towards
22 star formation regions which exhibit maser emission in the 107.0-GHz
3<SUB>1</SUB>-4<SUB>0</SUB> A<SUP>+</SUP> methanol transition, as well
as in the 6.6-GHz 5<SUB>1</SUB>-6<SUB>0</SUB> A<SUP>+</SUP> transition
characteristic of class II methanol maser sources. Each of these regions
was searched at 85.5 GHz, resulting in five detections, of which one
appears to be a newly discovered maser. For the 86.6-GHz transition,
observations were made of 18 regions, which yielded two detections,
but no new maser sources. This search demonstrates that emission from
the 6<SUB>-2</SUB>-7<SUB>-1</SUB> E and 7<SUB>2</SUB>-6<SUB>3</SUB>
A<SUP>-</SUP> transitions is rare. Detection of maser emission from
either of these transitions therefore indicates the presence of
special conditions, different from those in the majority of methanol
maser sources. We have observed temporal variability in the 86.6-GHz
emission towards 345.010+1.792, which - along with the very narrow line
width - confirms that the emission is a maser in this source. <P />We
have combined our current observations with published data for the
6.6-, 12.1-, 85.5-, 86.6-, 107.0-, 108.8- and 156.6-GHz transitions
for comparison with the maser model of Sobolev & Deguchi. Both
detections and non-detections are useful for setting limits on the
physical conditions in star-forming regions which contain methanol
maser emission. This has allowed us to estimate the likely ranges of
dust temperature, gas density and methanol column density, both for
typical methanol maser sources and for those sources which also show
107.0-GHz emission. The gas temperature can also be estimated for
those sources exhibiting masers at 85.5 and/or 86.6 GHz.
---------------------------------------------------------
Title: Simulations of precessing jets
Authors: Aloy, M. A.; Marti, J. M.; Ibanez, J. M.; Gomez, J. L.;
Agudo, I.; Mueller, E.
2003hsa..conf...23A Altcode:
We report on the results of a three-dimensional, relativistic,
hydrodynamical simulation of a precessing jet through which a compact
blob of matter is set to propagate. We conclude that the morphology of
superluminal sources is the result of a complex combination of phase
motions, viewing angle selection effects, and non-linear interactions
between perturbations and the underlying jet and/or external medium.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Western Magellanic Bridge HI
observations (Muller+, 2003)
Authors: Muller, E.; Staveley-Smith, L.; Zealey, W.; Stanimirovic, S.
2003yCat..73390105M Altcode:
Here we present high spatial and velocity resolution observations of the
Magellanic Bridge, conducted with both the Australia Telescope Compact
Array (ATCA) and with the Parkes telescope. <P />ATCA observation of
the 21-cm H I line were made over a 7x6deg<SUP>2</SUP> field using
the 375-m configuration of the ATCA. These observations were made over
three sessions: 1997 April 13, 15-16, 18; 1997 October 9-15; and 2000
January 29-February 2. The ATCA observations were made using a 4-MHz
bandwidth, with 1024 channels at a central frequency of 1.420GHz. <P
/>Parkes observations were made using the Multibeam receiver on the
64-m Parkes telescope, during 1999 November 2-8. Only the seven inner
receivers of the Multibeam array were used, with each beam having a FWHM
width of 14.1arcmin. 48 overlapping scans were made in declination,
using the on-the-fly mapping mode at 1deg/min in declination. The
scans were centred on RA=02h00m, DE=-72{deg}20', and extended 8{deg}
in declination and in RA, large enough to fully encompass the area
observed with the ATCA. <P />(1 data file).
---------------------------------------------------------
Title: High-resolution HI observations of the Western Magellanic
Bridge
Authors: Muller, E.; Staveley-Smith, L.; Zealey, W.; Stanimirović, S.
2003MNRAS.339..105M Altcode: 2002astro.ph.10615M
The 21-cm line emission from a 7 × 6 deg<SUP>2</SUP> region east of
and adjoining the Small Magellanic Cloud (SMC) has been observed with
the Australia Telescope Compact Array and the Parkes telescopes. This
region represents the westernmost part of the Magellanic Bridge,
a gas-rich tail extending ~14° to the Large Magellanic Cloud. A
rich and complex neutral hydrogen (HI) structure containing shells,
bubbles and filaments is revealed. On the larger scale, the HI of the
Bridge is organized into two velocity components. This bimodality,
which appears to originate in the SMC, converges to a single velocity
component within the observed region. A census of shell-like structures
suggests a shell population with characteristics similar to that of the
SMC. The mean kinematic age of the shells is ~6 Myr, in agreement with
the SMC shell population, but not with ages of OB clusters populating
the Magellanic Bridge, which are approximately a factor of 3 older. In
general, the projected spatial correlation of Bridge HI shells with
OB associations is poor and as such, there does not appear to be a
convincing relationship between the positions of OB associations and
that of expanding spherical HI structures. This survey has found only
one HI shell that has an identifiable association with a known Hα
shell. The origin of the expanding structures is therefore generally
still uncertain, although current theories regarding their formation
include gravitational and pressure instabilities, high-velocity cloud
collisions and ram pressure effects.
---------------------------------------------------------
Title: Detection of carbon monoxide within the Magellanic Bridge
Authors: Muller, E.; Staveley-Smith, L.; Zealey, W. J.
2003MNRAS.338..609M Altcode: 2002astro.ph..9523M
The Mopra 22-m and SEST 15-m telescopes have been used to detect and
partially map a region of <SUP>12</SUP>CO(1-0) line emission within
the Magellanic Bridge, a region lying between the Large and Small
Magellanic Clouds (LMC and SMC, respectively). The emission appears to
be embedded in a cloud of neutral hydrogen, and is in the vicinity of
an IRAS source. The CO emission region is found to have a 60 μm/100
μm flux density ratio typical for <SUP>12</SUP>CO(1-0) detections
within the SMC, although it has a significantly lower <SUP>12</SUP>CO
brightness and velocity width. These suggest that the observed region is
of a low metallicity, supporting earlier findings that the Magellanic
Bridge is not as evolved as the SMC and Magellanic Stream, which are
themselves of a lower metallicity than the Galaxy. Our observations,
along with empirical models based on SMC observations, indicate that
the radius of the detected CO region has an upper limit of ~16 pc. This
detection is, to our knowledge, the first detection of CO emission
from the Magellanic Bridge and is the only direct evidence of star
formation through molecular cloud collapse in this region.
---------------------------------------------------------
Title: C and O Explosive Nucleosynthesis in SNII coupled to
Multidimensional Hydrodynamics
Authors: Travaglio, C.; Kifonidis, K.; Müller, E.
2003ASPC..304..352T Altcode: 2003cnou.conf..352T
No abstract at ADS
---------------------------------------------------------
Title: Characteristic Numerical Relativity Applied to Hydrodynamic
Studies of Neutron Stars
Authors: Siebel, F.; Font, J. A.; Müller, E.; Papadopoulos, P.
2002nmgm.meet.1719S Altcode:
We present tests and results of a new axisymmetric, fully general
relativistic code with a perfect fluid matter field. Our implementation
is based on the null cone formalism of Bondi [2] and Tamburino-Winicour
[14,15]. 3D characteristic numerical relativity has been proven to
be very stable and accurate for evolutions of black hole spacetimes
[7]. Following previous work [8,1] we solve the Einstein equation
for a stress-energy tensor of a perfect fluid in characteristic
coordinates. The evolution of the matter fields is performed using
relativistic high-resolution shock-capturing schemes [4,11,13]
based upon Riemann solvers. The implementation of such schemes in
a 3D characteristic code is the current subject of a collaboration
(GRACE). In this work we restrict ourselves to axisymmetric spacetimes,
building on the vacuum code of Gómez, Papadopoulos and Winicour
[6]. Applications in spherical symmetry have been presented in
[11,12,9]...
---------------------------------------------------------
Title: Numerical Studies of Rotational Core Collapse in Axisymmetry
Using the Conformally Flat Metric Approach
Authors: Dimmelmeier, H.; Font, J. A.; Müller, E.
2002nmgm.meet.1695D Altcode:
Numerical simulations of matter flows evolving in the presence of strong
(and dynamic) gravitational fields are a highly complex problem. In
order to simplify the complexity of the gravitational field equations
of general relativity, Wilson and coworkers proposed an approximation
scheme, where the 3-metric γ<SUB>ij</SUB> is chosen to be conformally
fiat, which reduces the Einstein equations to a set of 5 coupled
elliptic equations. In this paper we present an axisymmetric general
relativistic hydrodynamic code which is based upon this approach,
and utilizes high-resolution shock-capturing schemes to solve the
hydrodynamic equations. We report on preliminary applications of
the code to rotating neutron stars and supernova core collapse in
axisymmetry. These results demonstrate the feasibility of the code to
handle a variety of relativistic astrophysical situations. The code will
be used in the near future to obtain information about gravitational
radiation from rotating gravitational collapse.
---------------------------------------------------------
Title: Relativistic simulations of rotational core collapse
II. Collapse dynamics and gravitational radiation
Authors: Dimmelmeier, H.; Font, J. A.; Müller, E.
2002A&A...393..523D Altcode: 2002astro.ph..4289D
We have performed hydrodynamic simulations of relativistic rotational
supernova core collapse in axisymmetry and have computed the
gravitational radiation emitted by such an event. The Einstein equations
are formulated using the conformally flat metric approximation, and
the corresponding hydrodynamic equations are written as a first-order
flux-conservative hyperbolic system. Details of the methodology and of
the numerical code have been given in an accompanying paper. We have
simulated the evolution of 26 models in both Newtonian and relativistic
gravity. The initial configurations are differentially rotating
relativistic 4 / 3 -polytropes in equilibrium which have a central
density of 10<SUP>10</SUP> g cm<SUP>-3</SUP>. Collapse is initiated
by decreasing the adiabatic index to some prescribed fixed value. The
equation of state consists of a polytropic and a thermal part for a
more realistic treatment of shock waves. Any microphysics like electron
capture and neutrino transport is neglected. Our simulations show that
the three different types of rotational supernova core collapse and
gravitational waveforms identified in previous Newtonian simulations
(regular collapse, multiple bounce collapse, and rapid collapse) are
also present in relativistic gravity. However, rotational core collapse
with multiple bounces is only possible in a much narrower parameter
range in relativistic gravity. The relativistic models cover almost
the same range of gravitational wave amplitudes ( 4 x 10<SUP>-21</SUP>
<=h<SUP>{</SUP>TT} <=3 x 10<SUP>-20</SUP> for a source at a
distance of 10 kpc) and frequencies ( 60 Hz <=nu <=1000 Hz )
as the corresponding Newtonian ones. Averaged over all models, the
total energy radiated in the form of gravitational waves is 8.2 x
10<SUP>-8</SUP> M<SUB>sun</SUB> c<SUP>2</SUP> in the relativistic
case, and 3.6 x 10<SUP>-8</SUP> M<SUB>sun</SUB> c<SUP>2</SUP> in the
Newtonian case. For all collapse models that are of the same type
in both Newtonian and relativistic gravity, the gravitational wave
signal is of lower amplitude. If the collapse type changes, either
weaker or stronger signals are found in the relativistic case. For
a given model, relativistic gravity can cause a large increase of
the characteristic signal frequency of up to a factor of five, which
may have important consequences for the signal detection. Our study
implies that the prospects for detection of gravitational wave signals
from axisymmetric supernova rotational core collapse do not improve
when taking into account relativistic gravity. The gravitational
wave signals obtained in our study are within the sensitivity range
of the first generation laser interferometer detectors if the source
is located within the Local Group. An online catalogue containing the
gravitational wave signal amplitudes and spectra of all our models is
available at the URL http://www.mpa-garching.mpg.de/Hydro/hydro.html.
---------------------------------------------------------
Title: Relativistic simulations of rotational core collapse
I. Methods, initial models, and code tests
Authors: Dimmelmeier, H.; Font, J. A.; Müller, E.
2002A&A...388..917D Altcode: 2002astro.ph..4288D
We describe an axisymmetric general relativistic code for rotational
core collapse. The code evolves the coupled system of metric and fluid
equations using the ADM 3 + 1 formalism and a conformally flat metric
approximation of the Einstein equations. Within this approximation the
ADM 3 + 1 equations reduce to a set of five coupled non-linear elliptic
equations for the metric components. The equations are discretized
on a 2D grid in spherical polar coordinates and are solved by means
of a Newton-Raphson iteration using a block elimination scheme to
solve the diagonally dominant, sparse linear system arising within
each iteration step. The relativistic hydrodynamics equations are
formulated as a first-order flux-conservative hyperbolic system and
are integrated using high-resolution shock-capturing schemes based on
Riemann solvers. We assess the quality of the conformally flat metric
approximation for relativistic core collapse and present a comprehensive
set of tests that the code successfully passed. The tests include
relativistic shock tubes, the preservation of the rotation profile
and of the equilibrium of rapidly and differentially rotating neutron
stars (approximated as rotating polytropes), spherical relativistic
core collapse, and the conservation of rest-mass and angular momentum
in dynamic spacetimes. The application of the code to relativistic
rotational core collapse, with emphasis on the gravitational waveform
signature, is presented in an accompanying paper.
---------------------------------------------------------
Title: Does the plasma composition affect the long-term evolution
of relativistic jets?
Authors: Scheck, L.; Aloy, M. A.; Martí, J. M.; Gómez, J. L.;
Müller, E.
2002MNRAS.331..615S Altcode: 2001astro.ph.11369S
We study the influence of the matter content of extragalactic jets
on their morphology, dynamics and emission properties. For this
purpose we consider jets of extremely different compositions,
including pure leptonic and baryonic plasmas. Our work is based
on two-dimensional relativistic hydrodynamic simulations of the
long-term evolution of powerful extragalactic jets propagating
into a homogeneous environment. The equation of state used in the
simulations accounts for an arbitrary mixture of electrons, protons
and electron-positron pairs. Using the hydrodynamic models, we have
also computed synthetic radio maps and the thermal bremsstrahlung
X-ray emission from their cavities. Although there is a difference of
about three orders of magnitude in the temperatures of the cavities
inflated by the simulated jets, we find that both the morphology and
the dynamic behaviour are almost independent of the assumed composition
of the jets. Their evolution proceeds in two distinct epochs. During
the first one, multidimensional effects are unimportant and the jets
propagate ballistically. The second epoch starts when the first larger
vortices are produced near the jet head, causing the beam cross-section
to increase and the jet to decelerate. The evolution of the cocoon
and cavity is in agreement with a simple theoretical model. The beam
velocities are relativistic (Γ ~=4) at kiloparsec scales, supporting
the idea that the X-ray emission of several extragalactic jets may
be due to relativistically boosted CMB photons. The radio emission
of all models is dominated by the contribution of the hotspots. All
models exhibit a depression in the X-rays surface brightness of the
cavity interior, in agreement with recent observations.
---------------------------------------------------------
Title: Gravitational waves from relativistic rotational core collapse
in axisymmetry
Authors: Dimmelmeier, H.; Font, J. A.; Müller, E.
2002CQGra..19.1291D Altcode:
We present results from simulations of axisymmetric relativistic
rotational core collapse. The main objective of our investigation is to
compute the waveforms of gravitational radiation emitted in such events,
extending previous Newtonian simulations to relativity. The general
relativistic hydrodynamic equations are formulated in flux-conservative
form and solved using a high-resolution shock-capturing scheme. The
Einstein equations are solved assuming a conformally flat 3-metric and
the quadrupole formula is used to extract waveforms of the gravitational
radiation emitted during the collapse. A comparison of our results with
those of Newtonian simulations shows that gravitational wave amplitudes
agree within 30%. Surprisingly, in some cases, relativistic effects
actually diminish the amplitude of the gravitational wave signal. We
further find that the parameter range of models suffering multiple
coherent bounces due to centrifugal forces is considerably smaller
than in Newtonian simulations.
---------------------------------------------------------
Title: Gravitational waves from rotational core collapse in the
conformally flat spacetime approximation
Authors: Dimmelemeier, H.; Font, J. A.; Müller, E.
2001AIPC..586..757D Altcode: 2001tsra.conf..757D
We have developed an axisymmetric general relativistic hydrodynamic
code based upon an approximation scheme recently proposed by Wilson
and coworkers, in which the 3-metric γ<SUB>ij</SUB> is conformally
flat, thus reducing the mathematical complexity of the Einstein metric
equations to a set of 5 coupled elliptic equations. Applications of
our code to rotational supernova core collapse are presented. We also
discuss first results concerning the emission of gravitational waves. .
---------------------------------------------------------
Title: Spherical collapse of supermassive stars: Neutrino emission
and gamma-ray bursts
Authors: Linke, F.; Font, J. A.; Janka, H. -T.; Müller, E.;
Papadopoulos, P.
2001A&A...376..568L Altcode: 2001astro.ph..3144L
We present the results of numerical simulations of the spherically
symmetric gravitational collapse of supermassive stars (SMS). The
collapse is studied using a general relativistic hydrodynamics
code. The coupled system of Einstein and fluid equations is solved
employing coordinates adapted to a foliation of the spacetime by
means of outgoing null hypersurfaces. The code contains an equation
of state which includes effects due to radiation, electrons and
baryons, and detailed microphysics to account for electron-positron
pairs. In addition energy losses by thermal neutrino emission are
included. We are able to follow the collapse of SMS from the onset of
instability up to the point of black hole formation. Several SMS with
masses in the range 5x 10<SUP>5</SUP> M<SUB>sun</SUB>-10<SUP>9</SUP>
M<SUB>sun</SUB> are simulated. In all models an apparent horizon forms
initially, enclosing the innermost 25% of the stellar mass. From the
computed neutrino luminosities, estimates of the energy deposition
by nu bar nu-annihilation are obtained. Only a small fraction of
this energy is deposited near the surface of the star, where, as
proposed recently by Fuller & Shi (\cite{Fuller98}), it could
cause the ultrarelativistic flow believed to be responsible for gamma
-ray bursts. Our simulations show that for collapsing SMS with masses
larger than 5x 10<SUP>5</SUP> M<SUB>sun</SUB> the energy deposition is
at least two orders of magnitude too small to explain the energetics of
observed long-duration bursts at cosmological redshifts. In addition,
in the absence of rotational effects the energy is deposited in a
region containing most of the stellar mass. Therefore relativistic
ejection of matter is impossible.
---------------------------------------------------------
Title: AMRA: An Adaptive Mesh Refinement hydrodynamic code for
astrophysics
Authors: Plewa, T.; Müller, E.
2001CoPhC.138..101P Altcode: 2000astro.ph.10626P
Implementation details and test cases of a newly developed hydrodynamic
code, amra, are presented. The numerical scheme exploits the adaptive
mesh refinement technique coupled to modern high-resolution schemes
which are suitable for relativistic and non-relativistic flows. Various
physical processes are incorporated using the operator splitting
approach, and include self-gravity, nuclear burning, physical
viscosity, implicit and explicit schemes for conductive transport,
simplified photoionization, and radiative losses from an optically thin
plasma. Several aspects related to the accuracy and stability of the
scheme are discussed in the context of hydrodynamic and astrophysical
flows.
---------------------------------------------------------
Title: Non-spherical core collapse supernovae and nucleosynthesis
Authors: Kifonidis, K.; Müller, E.; Plewa, T.
2001NuPhA.688..168K Altcode: 2000astro.ph.10085K
Motivated by observations of supernova SN 1987A, various authors
have simulated Rayleigh-Taylor (RT) instabilities in the envelopes
of core collapse supernovae (for a review, see Mueller 1998). The
non-radial motion found in these simulations qualitatively agreed with
observations in SN 1987A, but failed to explain the extent of mixing
of newly synthesized 56Ni quantitatively. Here we present results of a
2D hydrodynamic simulation which re-addresses this failure and covers
the entire evolution of the first 5 hours after core bounce.
---------------------------------------------------------
Title: Exploding and non-exploding stars: Coupling nuclear reaction
networks to multidimensional hydrodynamics
Authors: Kifonidis, K.; Plewa, T.; Müller, E.
2001AIPC..561...21K Altcode: 2001tsnp.symp...21K; 2000astro.ph.11206K
After decades of one-dimensional nucleosynthesis calculations,
the growth of computational resources has meanwhile reached a
level, which for the first time allows astrophysicists to consider
performing routinely realistic multidimensional nucleosynthesis
calculations in explosive and, to some extent, also in non-explosive
environments. In the present contribution we attempt to give a short
overview of the physical and numerical problems which are encountered
in these simulations. In addition, we assess the accuracy that can
be currently achieved in the computation of nucleosynthetic yields,
using multidimensional simulations of core collapse supernovae as an
example. .
---------------------------------------------------------
Title: On the Crystallization of Small Silica Particles in
Circumstellar Environments
Authors: John, M.; Müller, E.; Patzer, B.; Lüttke, M.; Sedlmayr, E.
2001AGM....18..P48J Altcode:
Infrared Space Observatory (ISO) observations have revealed the presence
of crystalline silicate dust in circumstellar environments of some
evolved stars (e.g. Waters et al. 1996, A&A 315, L361). Molster et
al. (2001, A&A 366, 923), for instance, reported the discovery of
a carbon-rich AGB star surrounded by a highly crystalline silicate dust
shell as indicated by the high resolution ISO-SWS spectrum. However, it
is still a matter of debate, whether the presence of crystalline dust is
restricted only to certain phases of the stellar evolution (e.g. Kemper
et al. 2000, A&A 369, 132). In order to understand the process,
which leads to the formation of crystalline structures in circumstellar
environments, the microphysical rearrangement of small silica particles
is investigated by means of molecular dynamic calculations. The results
indicate a dynamic coexistence of `amorphous'-like and symmetrical,
`crystalline' structures. Such rearrangement processes depend on the
energy transfer to the grain governed by the physical conditions of
the astrophysical environment. Therefore, the effect of the degree
of crystallinity on optical properties is additionally exemplified by
Mie calculations. Some implications regarding the condensation and the
mineralogy of silicate dust particles in the circumstellar environments
of AGB and post-AGB objects are discussed.
---------------------------------------------------------
Title: Optimization of a Tunable Quasi-Monochromatic X-ray Source
for Cell Irradiations
Authors: Neubert, W.; Enghardt, W.; Lehnert, U.; Müller, E.; Naumann,
B.; Panteleeva, A.; Pawelke, J.
2001amcr.conf..123N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Fluid Dynamics
Authors: Müller, E.
2000eaa..bookE2089M Altcode:
Fluid dynamics is a subfield of continuum mechanics which deals with the
theory of motion of a fluid (hydrodynamics) or gas (gas dynamics)....
---------------------------------------------------------
Title: Characteristic numerical relativity applied to hydrodynamic
studies of neutron stars
Authors: Siebel, F.; Font, J. A.; Mueller, E.; Papadopoulos, P.
2000gr.qc....11096S Altcode:
We present tests and results of a new axisymmetric, fully general
relativistic code capable of solving the coupled Einstein-matter
system for a perfect fluid matter field. Our implementation is
based on the Bondi metric, by which the spacetime is foliated with a
family of outgoing light cones. We use high-resolution shock-capturing
schemes to solve the fluid equations. The code can accurately maintain
long-term stability of a spherically symmetric, relativistic, polytropic
equilibrium model of a neutron star. In axisymmetry, we demonstrate
global energy conservation of a perturbed neutron star in a compactified
spacetime, for which the total energy radiated away by gravitational
waves corresponds to a significant fraction of the Bondi mass.
---------------------------------------------------------
Title: Numerical Simulations of the Precessing Jets of SS433
Authors: Muller, E.; Brinkmann, W.
2000IAUS..195..415M Altcode:
The unique Galactic object SS433 contains the best-studied relativistic
jets, and their physical parameters (velocity, temperature, density)
are known to an astronomically unprecedented accuracy, i.e., to factors
of order unity. The comparison of numerical simulations of these jets
with observations provides deeper insight into the SS433/W50 system and
is ideal for testing our understanding of the jet phenomenon in general.
---------------------------------------------------------
Title: Relativistic Jets from Collapsars
Authors: Aloy, M. A.; Müller, E.; Ibáñez, J. M.; Martí, J. M.;
MacFadyen, A.
2000ApJ...531L.119A Altcode: 1999astro.ph.11098A
Using a collapsar progenitor model of MacFadyen & Woosley,
we have simulated the propagation of an axisymmetric jet through a
collapsing rotating massive star with the GENESIS multidimensional
relativistic hydrodynamic code. The jet forms as a consequence of
an assumed (constant or variable) energy deposition in the range
of 10<SUP>50</SUP>-10<SUP>51</SUP> ergs s<SUP>-1</SUP> within a 30
deg cone around the rotation axis. The jet flow is strongly beamed
(approximately less than a few degrees), spatially inhomogeneous,
and time dependent. The jet reaches the surface of the stellar
progenitor (R<SUB>*</SUB>=2.98x10<SUP>10</SUP> cm) intact. At
breakout, the maximum Lorentz factor of the jet flow is 33. After
breakout, the jet accelerates into the circumstellar medium, whose
density is assumed to decrease exponentially and then become constant,
ρ<SUB>ext</SUB>=10<SUP>-5</SUP> g cm<SUP>-3</SUP>. Outside the star,
the flow begins to expand laterally also (v~c), but the beam remains
very well collimated. At a distance of 2.54 R<SUB>*</SUB>, where the
simulation ends, the Lorentz factor has increased to 44.
---------------------------------------------------------
Title: Nucleosynthesis and Clump Formation in a Core-Collapse
Supernova
Authors: Kifonidis, K.; Plewa, T.; Janka, H. -Th.; Müller, E.
2000ApJ...531L.123K Altcode: 1999astro.ph.11183K
High-resolution two-dimensional simulations were performed for the first
5 minutes of the evolution of a core-collapse supernova explosion in a
15 M<SUB>solar</SUB> blue supergiant progenitor. The computations start
shortly after bounce and include neutrino-matter interactions by using
a lightbulb approximation for the neutrinos and a treatment of the
nucleosynthesis due to explosive silicon and oxygen burning. We find
that newly formed iron-group elements are distributed throughout the
inner half of the helium core by Rayleigh-Taylor instabilities at the
(Ni + Si)/O and (C + O)/He interfaces, seeded by convective overturn
during the early stages of the explosion. Fast-moving nickel mushrooms
with velocities up to ~4000 km s<SUP>-1</SUP> are observed. This
offers a natural explanation for the mixing required in light-curve
and spectral synthesis studies of Type Ib explosions. A continuation
of the calculations to later times, however, indicates that the iron
velocities observed in SN 1987A cannot be reproduced because of a
strong deceleration of the clumps in the dense shell left behind by
the shock at the He/H interface.
---------------------------------------------------------
Title: Two-dimensional versus Three-dimensional Supernova Hydrodynamic
Instability Growth
Authors: Kane, J.; Arnett, D.; Remington, B. A.; Glendinning, S. G.;
Bazán, G.; Müller, E.; Fryxell, B. A.; Teyssier, R.
2000ApJ...528..989K Altcode:
Numerical simulations using the SN hydrodynamics code PROMETHEUS are
carried out to study the difference between growth of two-dimensional
versus three-dimensional single-mode perturbations at the He-H and O-He
interfaces of SN 1987A. We find that in the rest frame of an unperturbed
one-dimensional interface, a three-dimensional single-mode perturbation
grows ~30%-35% faster than a two-dimensional single-mode perturbation,
when the wavelengths are chosen to give the same linear stage growth in
the planar limit. In simulations where we impose single-mode density
perturbations in the O layer of the initial model and random velocity
perturbations in the postshock fluid near the He-H interface, we
find that both axisymmetric O spikes and three-dimensional O spikes
penetrate significantly further than two-dimensional O spikes. The
difference between two dimensions and three dimensions predicted by
our calculations is not enough to account for the difference between
observed <SUP>56</SUP>Co velocities in SN 1987A and the results of
previous two-dimensional simulations of SN 1987A, but our results
suggest that the real three-dimensional hydrodynamics are noticeably
different than the two-dimensional simulations predict.
---------------------------------------------------------
Title: The First Hours of a Core Collapse Supernova
Authors: Kifonidis, K.; Plewa, T.; Janka, H. -Th.; Müller, E.
2000nuas.conf...60K Altcode: 2000astro.ph..7282K
New two-dimensional, high-resolution calculations of a core collapse
supernova in a 15 Msol blue supergiant are presented, which cover
the entire evolution from shock revival until the first few hours
of the explosion. Explosive nucleosynthesis, its dependence upon
convective mixing during the first second of the evolution and the
growth of Rayleigh-Taylor instabilities at the composition interfaces
of the progenitor star are all modeled consistently and allow for a
comparison with observational data. We confirm our earlier findings,
that the perturbations induced by neutrino driven convection are
sufficiently strong to seed large-scale Rayleigh-Taylor mixing and
to destroy the onion-shell structure of the stellar He-core. As
in our earlier calculations, the strong deceleration of the nickel
clumps in the layers adjacent to the He/H interface suggests that the
high velocities of iron-group elements observed in SN 1987A cannot be
explained on the basis of currently favored progenitor models. Possible
solutions to this dilemma and the implications of the mixing for type
Ib explosions are briefly discussed.
---------------------------------------------------------
Title: The First Five Minutes of a Core Collapse Supernova:
Multidimensional Hydrodynamic Models
Authors: Kifonidis, K.; Plewa, T.; Janka, H. -Th.; Mueller, E.
1999astro.ph.11407K Altcode:
We present results of high-resolution two-dimensional simulations which
follow the first five minutes of a core collapse supernova explosion
in a 15 solar mass blue supergiant progenitor. The computations start
shortly after core bounce and include neutrino-matter interactions by
using a light-bulb approximation for the neutrinos, and a treatment
of the nucleosynthesis due to explosive silicon and oxygen burning. We
find that newly formed iron-group elements are distributed throughout a
significant fraction of the stellar helium core by the concerted action
of convective and Rayleigh-Taylor instabilities. Fast moving nickel
mushrooms with velocities up to 4000 km/s are observed. A continuation
of the calculations to later times, however, indicates, that the iron
velocities observed in SN 1987 A cannot be reproduced due to a strong
deceleration of the clumps during their interaction with the dense shell
left behind by the shock at the He/H interface. Therefore, we cannot
confirm the claim that convective "premixing" of the nickel in the early
phases of the explosion solves the problem of the high iron velocities.
---------------------------------------------------------
Title: An exact Riemann Solver for multidimensional special
relativistic hydrodynamics
Authors: Pons, J.; Marti, J. Ma.; Muller, E.
1999astro.ph.10462P Altcode:
We have generalised the exact solution of the Riemann problem in
special relativistic hydrodynamics for arbitrary tangential flow
velocities. The solution is obtained by solving the jump conditions
across shocks plus an ordinary differential equation arising from the
self-similarity condition along rarefaction waves, in a similar way as
in purely normal flow. The dependence of the solution on the tangential
velocities is analysed. This solution has been used to build up an
exact Riemann solver implemented in a multidimensional relativistic
(Godunov-type) hydro-code.
---------------------------------------------------------
Title: High-Resolution Three-dimensional Simulations of Relativistic
Jets
Authors: Aloy, M. A.; Ibáñez, J. M.; Martí, J. M.; Gómez, J. -L.;
Müller, E.
1999ApJ...523L.125A Altcode: 1999astro.ph..6428A
We have performed high-resolution three-dimensional simulations
of relativistic jets with beam-flow Lorentz factors of up to 7,
a spatial resolution of 8 cells per beam radius, and up to 75
normalized time units in order to study the morphology and dynamics
of three-dimensional relativistic jets. Our simulations show that the
coherent fast backflows found in axisymmetric models are not present in
three-dimensional models. We further find that when the jet is exposed
to nonaxisymmetric perturbations, (1) it does not display the strong
perturbations found for three-dimensional classical hydrodynamic and MHD
jets (at least during the period of time covered by our simulations) and
(2) it does propagate according to the one-dimensional estimate. Small
three-dimensional effects in the relativistic beam give rise to a lumpy
distribution of apparent speeds like that observed in M87. The beam is
surrounded by a boundary layer of high specific internal energy. The
properties of this layer are briefly discussed.
---------------------------------------------------------
Title: GENESIS: A High-Resolution Code for Three-dimensional
Relativistic Hydrodynamics
Authors: Aloy, M. A.; Ibáñez, J. M.; Martí, J. M.; Müller, E.
1999ApJS..122..151A Altcode: 1999astro.ph..3352A
The main features of a three-dimensional, high-resolution special
relativistic hydro code based on relativistic Riemann solvers
are described. The capabilities and performance of the code are
discussed. In particular, we present the results of extensive
test calculations that demonstrate that the code can accurately and
efficiently handle strong shocks in three spatial dimensions. Results of
the performance of the code on single and multiprocessor machines are
given. Simulations (in double precision) with <=7×10<SUP>6</SUP>
computational cells require less than 1 Gbyte of RAM memory and
~7×10<SUP>-5</SUP> CPU s per zone and time step (on a SCI Cray-Origin
2000 with a R10000 processor). Currently, a version of the numerical
code is under development, which is suited for massively parallel
computers with distributed memory architecture (such as, e.g.,
Cray T3E).
---------------------------------------------------------
Title: The consistent multi-fluid advection method
Authors: Plewa, T.; Müller, E.
1999A&A...342..179P Altcode: 1998astro.ph..7241P
Simple modifications for higher-order Godunov-type difference schemes
are presented which allow for accurate advection of multi-fluid flows
in hydrodynamic simulations. The constraint that the sum of all mass
fractions has to be equal to one in every computational zone throughout
the simulation is fulfilled by renormalizing the mass fractions
during the advection step. The proposed modification is appropriate
for any difference scheme written in conservation form. Unlike other
commonly used methods it does not violate the conservative character
of the advection method. A new steepening mechanism, which is based on
modification of interpolation profiles, is used to reduce numerical
diffusion across composition discontinuities. Additional procedures
are described, which are necessary to enforce monotonicity. Several
numerical experiments are presented which demonstrate the capability
of our Consistent Multi-fluid Advection (CMA) method in case of smooth
and discontinuous distributions of fluid phases and under different
hydrodynamic conditions. It is shown that due to the reduced diffusivity
of the proposed scheme the abundance of some heavy elements obtained
from hydrodynamic simulations of type II supernova explosions can
change by a factor of a few in the most extreme cases.
---------------------------------------------------------
Title: Book Review: Computational methods for astrophysical fluid
flow / Springer Verlag, 1998
Authors: Leveque, R. J.; Mihalas, D.; Dorfi, E. A.; Müller, E.
1999IrAJ...26...73L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Multi-Dimensional Numerical Simulations of Core-Collapse
Supernovae
Authors: Kifonidis, Konstantinos; Plewa, T.; Janka, H. -Th.;
Mueller, E.
1999asra.conf..141K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Simulations of non-axisymmetric rotational core collapse
Authors: Rampp, M.; Mueller, E.; Ruffert, M.
1998A&A...332..969R Altcode: 1997astro.ph.11122R
We report on the first three-dimensional hydrodynamic simulations of
secular and dynamical non-axisymmetric instabilities in collapsing,
rapidly rotating stellar cores which extend well beyond core bounce. The
resulting gravitational radiation has been calculated using the
quadrupole approximation. We find that secular instabilities do not
occur during the simulated time interval of several 10ms. Models
which become dynamically unstable during core collapse show a strong
nonlinear growth of non-axisymmetric instabilities. Both random and
coherent large scale initial perturbations eventually give rise to
a dominant bar-like deformation <SUP>(+/- imphi </SUP> with m=2). In
spite of the pronounced tri-axial deformation of certain parts of the
core no considerable enhancement of the gravitational radiation is
found. This is due to the fact that rapidly rotating cores re-expand
after core bounce on a dynamical time scale before non-axisymmetric
instabilities enter the nonlinear regime. Hence, when the core becomes
tri-axial, it is no longer very compact.
---------------------------------------------------------
Title: Explosive Nucleosynthesis: Coupling Reaction Networks to
Amr Hydrodynamics
Authors: Kifonidis, K.; Plewa, T.; Müller, E.
1998nuas.conf...25K Altcode: 1998astro.ph..5158K
In recent years the technique of Adaptive Mesh Refinement (AMR) has
been successfully applied to several astrophysical problems. This
method should also allow a consistent multi-dimensional modelling
of supernova explosions. In this contribution we address some of the
computational difficulties encountered when trying to apply the AMR
method to explosive nucleosynthesis and supernova envelope ejection.
---------------------------------------------------------
Title: The Precessing Jets of SS433
Authors: Brinkmann, W.; Müller, E.
1998ajop.conf..211B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Convection in newly born neutron stars
Authors: Keil, W.; Janka, H. -T.; Müller, E.
1998sese.conf..557K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Gravitational Radiation from Core Collapse Supernovae
Authors: Müller, E.
1998grwa.conf...48M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Convection in protoneutron stars.
Authors: Keil, W.; Janka, H. -T.; Müller, E.
1998tsra.conf..717K Altcode:
Convectively enhanced neutrino (ν) luminosities from the protoneutron
star (PNS) can provide an essential condition for a Type-II supernova
explosion. Very recent two-dimensional, self-consistent, general
relativistic simulations of the cooling of a newly-formed neutron star
demonstrate and confirm the possibility that quasi-Ledoux convection,
driven by negative lepton number and entropy gradients, may encompass
the whole PNS within less than 1 s and can lead to an increase of the
neutrino fluxes by up to a factor of two.
---------------------------------------------------------
Title: Convection in Protoneutron Stars
Authors: Müller, E.
1998tsra.conf..717M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Long Term Evolution of Powerful Relativistic Jets
Authors: Martí, J. M.; Müller, E.; Ibañez, J. M.
1998ajop.conf..149M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Supernova hydrodynamics experiments on the Nova laser
Authors: Kane, J.; Arnett, D.; Remington, B. A.; Glendinning, S. G.;
Rubenchik, A.; Drake, R. P.; Fryxell, B. A.; Muller, E.
1997AAS...191.3911K Altcode: 1997BAAS...29.1266K
The critical roles of hydrodynamic instabilities in SN 1987A and in ICF
are well known; 2D-3D differences are important in both areas. In a
continuing project at Lawrence Livermore National Laboratory (LLNL),
the Nova Laser is being used in scaled laboratory experiments of
hydrodynamic mixing under supernova-relevant conditions. Numerical
simulations of the experiments are being done, using LLNL hydro codes,
and astrophysics codes used to model supernovae. Initial investigations
with two-layer planar packages having 2D sinusoidal interface
perturbations are described in Ap.J. 478, L75 (1997). Early-time
simulations done with the LLNL 1D radiation transport code HYADES
are mapped into the 2D LLNL code CALE and into the multi-D supernova
code PROMETHEUS. Work is underway on experiments comparing interface
instability growth produced by 2D sinusoidal versus 3D cross-hatch and
axisymmetric cylindrical perturbations. Results of the simulations will
be presented and compared with experiment. Implications for interpreting
supernova observations and for supernova modelling will be discussed. *
Work performed under the auspices of the U.S. Department of Energy
by the Lawrence Livermore National Laboratory under contract number
W-7405-ENG-48.
---------------------------------------------------------
Title: Rapidly rotating stars with either H burning or He burning
core.
Authors: Shindo, M.; Hashimoto, M.; Eriguchi, Y.; Mueller, E.
1997A&A...326..177S Altcode:
We have succeeded in constructing structures of realistic models for
rapidly rotating inhomogeneous stars in the nuclear burning stages. The
nuclear reaction networks both for CNO cycle and for helium burning
have been successfully included in the 2D numerical code. Concerning
the equation of state and the opacity, we have used the same ones as
used in calculations of spherical stellar structures. The rotation law
in our computations covers uniform rotation and differential rotation
with rapidly rotating cores. We have computed several equilibrium
sequences of massive stars up to models just before the mass begins to
shed from the equatorial surface (critical models). We mainly discuss
two critical sequences of models: 1) 18M<SUB>sun</SUB>_ stars with
hydrogen burning cores and 2) 5M<SUB>sun</SUB>_ helium stars with helium
burning cores. It is found that the effect of rotation on the structure
is similar for both sequences. For uniformly rotating hydrogen burning
stars the luminosity decrease is about 6.4% which is consistent with the
results obtained by other authors. For models which have the angular
momentum distribution concentrated toward the center, we get very
flattened shapes of stellar surfaces. Compared with the non-rotating
models, decrease of the luminosity is found to be 16% for the critical
models if the total angular momentum is less than 10^53^g.cm^2^/s and if
a toroid-like structure of the density distribution does not appear. On
the other hand, decrease of the luminosity becomes significant for
stars with the toroid-like structure of the density distribution,
i.e. for toroidal distribution of the energy source. It is remarkable
that stars whose ratio of the polar radius to the equatorial radius
is less than 0.25 have extended envelopes due to a delicate balance
between the gravitational force and the centrifugal force.
---------------------------------------------------------
Title: Gravitational radiation from core-collapse supernovae
Authors: Müller, E.
1997CQGra..14.1455M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Morphology and Dynamics of Relativistic Jets
Authors: Martí, J. M.; Müller, E.; Font, J. A.; Ibáñez, J. M. Z.;
Marquina, A.
1997ApJ...479..151M Altcode:
We present a comprehensive analysis of the morphology and dynamics
of relativistic pressure-matched axisymmetric jets. The numerical
simulations have been carried out with a high-resolution shock-capturing
hydrocode based on an approximate relativistic Riemann solver derived
from the spectral decomposition of the Jacobian matrices of relativistic
hydrodynamics. We discuss the dependence of the jet morphology on
several parameters, paying special attention to the relativistic
effects caused by high Lorentz factors and large internal energies of
the beam flow. The parameter space of our analysis is spanned by the
ratio of the beam and ambient medium rest mass density (η), the beam
Mach number (M<SUB>b</SUB>), the beam Lorentz factor (W<SUB>b</SUB>),
and the adiabatic index (γ) of the equation of state (assuming an
ideal gas). Both the ultrarelativistic regime (W<SUB>b</SUB> >= 20)
and the hypersonic regime (relativistic Mach number greater than 100)
have been studied. <P />Our results show that the enhancement of the
effective inertial mass of the beam due to relativistic effects (through
the specific enthalpy and the Lorentz factor) makes relativistic jets
significantly more stable than Newtonian jets. We find that relativistic
jets propagate very efficiently through the ambient medium, at speeds
that agree very well with those obtained from an estimate based on
a one-dimensional momentum balance. The propagation efficiency of a
relativistic jet is an increasing function of the beam flow velocity. <P
/>Relativistic jets seem to give rise to two different morphologies,
according to the relevance of relativistic effects. Hot beams (i.e.,
with internal energies comparable to the beam rest-mass energy) show
little internal structure (as they are almost in pressure equilibrium
with their surroundings) and relatively smooth cocoons forming lobes
near the head of the jet. Highly supersonic models, in which the
kinematic relativistic effects due to high beam flow Lorentz factors
dominate, display extended cocoons that are overpressured with respect
to the environment. The cocoon thickness decreases, and its mean
pressure increases with increasing beam Lorentz factor.
---------------------------------------------------------
Title: Dynamics and gravitational wave signature of axisymmetric
rotational core collapse.
Authors: Zwerger, T.; Mueller, E.
1997A&A...320..209Z Altcode:
We have carried out a comprehensive parameter study of the dynamics
of rotational core collapse in massive stars. The iron cores have
been approximated by axisymmetric rotating {GAMMA}=4/3 polytropes
in rotational equilibrium. Any transport effects by neutrinos have
been neglected. We have computed 18 initial models which differ by
their amount of rotational energy and their distribution of angular
momentum. The initial models range from slowly to rapidly rotating and
from rigidly to extremely differentially rotating configurations. The
collapse was induced by suddenly reducing the adiabatic index {GAMMA} to
a value {GAMMA}_r_ with 1.28<={GAMMA}_r_<=1.325. The stiffening of
the equation of state at nuclear matter density and the thermal pressure
in the matter heated by the prompt shock was simulated by means of a
simplified analytic equation of state consisting of a polytropic and a
thermal part. The evolution of a total of 78 models was followed well
beyond core bounce using a two dimensional Newtonian hydrodynamic
finite difference code. A subset of models suffers a bounce caused
by centrifugal forces at sub-nuclear densities. For a given rotation
rate the bounce density decreases with increasing {GAMMA}_r_ and with
increasing degree of differential rotation. Models suffering a bounce
due to (or mainly due to) centrifugal forces show large amplitude
oscillations of the inner core the central density varying by more
than a factor of ten. In several models the rotation rate exceeds the
critical value, where MacLaurin spheroids become secularly unstable
against tri-axial perturbations. Two of the most differentially and
rapidly rotating models reach ({GAMMA}_r_=1.30) and even exceed
({GAMMA}_r_=1.28) the critical value for axisymmetric dynamical
stability. We have also computed the gravitational (quadrupole)
wave signal emitted by our core collapse models. We find both
type I (spike + ring-down) and type II (several distinct spikes)
gravitational wave signals. Which type occurs is solely determined by
the adiabatic index. Signals of type I are produced by models with a
"soft" equation of state ({GAMMA}_r_<~1.31), while signals of type
II require a "stiff" equation of state ({GAMMA}_r_>1.32). Decreasing
the adiabatic index from 1.325 to 1.28 and keeping the other model
parameters fixed, we observe a smooth transformation of the signal
type. For {GAMMA}_r_=1.28 a third signal type is observed, which shows
a large positive and a smaller negative wave amplitude just before
and after bounce. Signals of type III are not found for extremely
differentially rotating initial models. The energy spectra cover
a frequency range of 50Hz<~ν<~3kHz, but most of the power is
emitted between 500Hz and 1kHz. Models bouncing at sub-nuclear densities
have spectra, which drop extremely rapidly above 1kHz, and models
with a type II wave signal have spectra, which show characteristic
oscillations. These oscillations vanish when the signal type changes
to type I. The spectra are neither very sensitive to the rotation
rate nor to the degree of differential rotation. The total amount
of energy radiated in form of gravitational waves lies in the range
6x10^-11^M<SUB>sun</SUB>_c^2^<~E_GW_<~8x10^-8^M<SUB>sun</SUB>_c^2^.
The corresponding dimensionless wave amplitudes are in the range
4x10^-25^<~h<~4x10^-23^ for a source at a distance of 10 Mpc. The
largest signals are either produced by models which are initially
slowly rotating and have an adiabatic index {GAMMA}_r_>=1.32, or
which are initially rapidly and strongly differentially rotating and
have a relatively small adiabatic index ({GAMMA}_r_<=1.30).
---------------------------------------------------------
Title: 3-D Time Dependent Hydrodynamic Simulations of the Processing
Jets of SS433
Authors: Müller, E.; Brinkmann, W.
1997xisc.conf..455M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Gravitational radiation from convective instabilities in Type
II supernova explosions.
Authors: Mueller, E.; Janka, H. -T.
1997A&A...317..140M Altcode:
We present two- and three-dimensional simulations of convective
instabilities during the first second of a Type II supernova
explosion. Convective overturn occurs in two distinct, spatially
well separated regions: (i) inside the proto-neutron star immediately
below the neutrinosphere (r<~50km) and (ii) in the neutrino-heated
"hot-bubble" region interior to the outward propagating revived shock
wave (100km<~r<~1000km). We have calculated the gravitational wave
signature of both convective instabilities including the quadrupole
waveforms, the energy spectra, and the total amount of the emitted
gravitational wave energy. Moreover, we have estimated the amplitude
and energy of gravitational waves associated with the anisotropic
neutrino emission that is caused by the convective transport of
neutrinos and by aspherical perturbations of temperature and density
in the neutrinospheric region. For a supernova located at a distance
of 10 kpc the maximum dimensionless gravitational wave amplitudes
due to convective mass motions range from |h^TT^|=~2x10^-22^ for the
three-dimensional simulation to |h^TT^|=~3x10^-21^ for the most strongly
radiating two-dimensional model. The total emitted energy varies from
3x10^-14^M<SUB>sun</SUB>_c^2^ to 5x10^-10^M<SUB>sun</SUB>_c^2^. The
convective mass motions inside the proto-neutron star produce a stronger
signal than convection in region (ii) with up to a factor of 10 larger
amplitudes and 1000 times more gravitational wave energy. Because
of smaller convective eddies and structures and slower overturn
velocities, the wave amplitudes of three-dimensional models are more
than a factor of 10 smaller, and the energy emitted in gravitational
waves is almost 3 orders of magnitude less than in the corresponding
two-dimensional situation. In two dimensions the gravitational wave
amplitude associated with the anisotropic emission of neutrinos can be
larger (factor 5) than the wave amplitude due to mass motions in the
proto-neutron star, although the energy in the neutrino tidal field
is 20 times smaller. In three dimensions the neutrino gravitational
wave amplitude is reduced by a factor of about 10 and the gravitational
wave energy by a factor of roughly 100 relative to the two-dimensional
results. Nevertheless, the neutrino tidal field is more than a factor
of 10 larger than the gravitational wave amplitude from mass motions
and the corresponding gravitational wave energies can be of similar
size. Most of the gravitational radiation from convection inside
the proto-neutron star is emitted in the frequency band 100-1000Hz,
while convective motions in the hot-bubble region generate waves from
several 100Hz down to a few Hz. Gravitational waves from the anisotropic
neutrino emission have most power at frequencies between some 10Hz and
a few 100Hz and a low-frequency contribution at about 1Hz to several
Hz. Features in the gravitational-wave signal from the neutrino-heated
region are well correlated with structures in the neutrino signal,
both being associated with sinking and rising lumps of matter and
with temporal variations of aspherical accretion flows towards the
proto-neutron star. A simultaneous measurement of both signals would
impose important constraints on the dynamics of Type II supernovae
and theoretical models of the explosion mechanism.
---------------------------------------------------------
Title: Gravitational Waves from Core Collapse Supernovae
Authors: Müller, E.
1997rggr.conf..273M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Bending Relativistic Jets in AGNs
Authors: Plewa, T.; Marti, J. M.; Muller, E.; Rozyczka, M.; Sikora, M.
1997rja..proc..104P Altcode: 1997astro.ph..6124P
We present simulations of relativistic jets propagating in a nonuniform
medium. Specifically, we study the bending of jets propagating obliquely
to the vector of the density-gradient. Our results are applied to
the NGC 4258, where such a medium is assumed to be provided by the
atmosphere of the sub-parsec accretion disk tilted with respect to
the original direction of the jet propagation. As a result, the jet
is bent on a scale comparable to the density scaleheight of the disk
atmosphere. The magnitude of the bending effect is found to be largest
for light jets with low Lorentz factors. The predicted direction of
bending is consistent with the observations.
---------------------------------------------------------
Title: Parallelizing a multi-dimensional, explicit, finite difference
hydrodynamic code.
Authors: Müller, E.
1996AGAb...12..111M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Book reviews
Authors: Humphreys, R. M.; Kemp, S.; Savonije, G.; van der Hucht,
K. A.; van der Kruit, P. C.; Miley, G.; Bumba, V.; van Nieuwkoop,
J.; van Hoolst, T.; Cox, A.; Rutten, R. J.; Kleczek, J.; de Jager,
Cornelis; Jerzykiewicz, M.; Zwaan, C.; Poedts, S.; Sakai, Jun-Ichi;
Pecker, J. -C.; Heikkila, W.; de Jong, T.; Wilson, P. R.; Müller,
E. A.; Hoyng, P.; Icke, V.; Shore, S. N.; Achterberg, A.; Lucchin, F.;
Butcher, H.; Ne'Eman, Y.; Heidmann, J.; Belton, M. J. S.; de Graauw,
Th.; Waters, L. B. F. M.; Pacini, F.; Hultqvist, B.; Akasofu, S. -I.;
Vial, J. -C.; Schatzman, E.; van der Laan, H.; Cole, K. D.; Vanbeveren,
D.; Southwood, D.; van der Klis, M.; Katgert, Peter
1996SSRv...76..339H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Neutrino heating, convection, and the mechanism of Type-II
supernova explosions.
Authors: Janka, H. -T.; Mueller, E.
1996A&A...306..167J Altcode:
The role of neutrino heating and convective processes in the
explosion mechanism of Type-II supernovae is investigated by one- and
two-dimensional hydrodynamical simulations of the long-time evolution
of the collapsed stellar core after the bounce at nuclear matter
density and after the associated formation of the supernova shock. The
parameters describing the neutrino emission from the collapsed stellar
core are systematically varied. The possibility to obtain explosions
turns out to be very sensitive to the physical conditions in and at the
protoneutron star, in particular to its contraction and to the neutrino
cooling inside of the gain radius. Yet, above a certain threshold
for the core neutrino luminosity, stable and energetic explosions can
be obtained in spherical symmetry, provided the energy deposition by
neutrinos remains strong for a sufficiently long period. The explosion
energy and time scale critically depend on the neutrino fluxes during
the shock revival phase and on their temporal decay during the first
few 100ms after shock formation. The threshold luminosity is a very
sensitive function of the shock stagnation radius, because small radii
of the stalled prompt shock lead to significantly higher neutrino loss
from the hot and compact postshock layers, cause the region of neutrino
heating to be very narrow, and reduce the heating time scale of the
matter due to the high infall velocity. Repeating the simulations in
two dimensions we find that strong convective processes occur in the
collapsed stellar core in two spatially separate regions. One region of
convection lies inside the neutrinosphere and another one is located
in the neutrino-heated layer below the shock front. The convective
mixing around the neutrinosphere is mainly driven by the negative
lepton gradient, which is maintained by rapid loss of leptons from
the semitransparent layers at the neutrinosphere. This considerably
speeds up the deleptonization of the outer layers of the collapsed
stellar core. Even 0.5 seconds after bounce a quasi-stationary
pattern of convective motion is still present in the protoneutron
star. Three-dimensional simulations reveal that rising and sinking
convective elements have about half the size as in two dimensions with
angular diameters between 10deg and 15deg, which causes corresponding
anisotropies of the neutrino emission from the core. The large-scale
convective overturn that takes place between the shock and the
position of maximum neutrino heating is able to efficiently transport
energy from the heated layer into the postshock region. This helps to
stabilize the shock revival during the critical phase. It also leads
to a faster increase and earlier saturation of the explosion energy,
both because neutrino-heated material quickly moves out of the heating
region and energy loss by the re-emission of neutrinos is reduced. The
overturn pattern shows downflows of matter in narrow flux tubes and
rising bubbles with typical angular extensions of 30deg to 60deg (in
two dimensions). The material falling towards the neutron star loses
lepton number, but readily absorbs energy in the neutrino-heated region,
before it rises again. When the explosion gains momentum, this matter
is not accreted onto the cooler, neutron-rich protoneutron star any
more. After about 200-300ms the convective shell gets decoupled from the
heating region and starts to move away from the neutron star to expand
in an essentially self-similar way as a thick layer behind the outward
propagating shock. The nearly spherically symmetrical "hot-bubble"
region begins to develop and turbulence around the protoneutron
star ceases. When the supernova shock passes the entropy step of the
Si-O-interface about 400-500ms after bounce, the density inversion
between the low-density hot-bubble region and the inhomogeneous shell
steepens into a strong reverse shock that forms a sharp discontinuity in
the neutrino wind from the nascent neutron star. The supernova shock is
significantly deformed and velocity, density, temperature, and entropy
in the postshock region exhibit large-scale variations with a contrast
of up to a factor of 3. This must have consequences for the formation
and spatial distribution of nucleosynthesis products and might help
to explain the clumpiness, anisotropies, envelope and mantle mixing,
and large velocities of iron group nuclei which were observed in the
ejecta of SN 1987A and other supernovae. Although in this respect
of essential importance, convection in the postshock region does
not seem to be indispensable to get successful Type-II explosions
via the neutrino-heating mechanism, nor do our simulations allow
for the conclusion that its presence inevitably makes the mechanism
successful and the explosions very energetic. As in spherical symmetry,
the explosion energy and time scale are influenced by the contraction
of the cooling neutron star and are very sensitive to the neutrino
energy deposition and the size of the neutrino fluxes during a period
of several hundred milliseconds after core bounce.
---------------------------------------------------------
Title: Morphology and dynamics of relativistic jets.
Authors: Müller, E.; Martí, J. M.; Ibáñez, J. M.
1996AGAb...12...66M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Individual Light Curve FITS of SN IA and H sub 0
Authors: Hoflich, P. A.; Muller, E.; Khokhlov, A.
1996ssr..conf...29H Altcode: 1996IAUCo.145...29H
No abstract at ADS
---------------------------------------------------------
Title: Equilibrium structures of self-gravitating disks.
Authors: Hashimoto, M.; Eriguchi, Y.; Arai, K.; Müller, E.
1996bpad.conf..269H Altcode:
The authors investigate equilibrium structures of rapidly rotating
toroids and disks with self-gravity using the two-dimensional code. Two
rotational laws are assumed: (1) rotation having constant specific
angular momentum (j-const law) and (2) Keplerian rotation. Equilibrium
sequences are calculated with the specified central temperature of
the toroid and the mass of the central object. Configuration of hot
toroids resembles to that of a thick disk. In particular, the central
temperature of a toroid exceeds 10<SUP>9</SUP>K and the luminosity
exceeds the Eddington luminosity considerably. It is found that the
Keplerian disks with self-gravity have thin, slim, and fat shapes
which depend on the distance between the central object and the disk,
and also on the mass ratio between the central object and the disk.
---------------------------------------------------------
Title: A Numerical Study of Relativistic Jets
Authors: Font, J. A.; Marti, J. M.; Ibanez, J. M.; Muller, E.
1996IAUS..175..435F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Gravitational wave signal of rotational core collapse.
Authors: Müller, E.; Zwerger, T.
1996AGAb...12...48M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Morphology and Dynamics of Highly Supersonic Relativistic Jets
Authors: Marti, J. M. A.; Muller, E.; Font, J. A.; Ibanez, J. Ma.
1995ApJ...448L.105M Altcode:
We present a simulation of a diffuse ( eta = 0.01), high-beam Mach
number (Mb = 6.0), relativistic (beam Lorentz factor 22.4) axisymmetric
jet, and we discuss its morphology and dynamics. The jet exhibits a
prominent structure of oblique shocks inside the beam and possesses
an extensive cocoon. This result is qualitatively different from
the findings of other recent simulations of low-beam Mach number
relativistic jets, where both features are absent. We find that the
jet propagates very efficiently through the ambient medium. Its mean
velocity is 15 times larger than that expected from classical (i.e.,
nonrelativistic) simulations. The simulations are performed with a
high-resolution shock-capturing scheme using a Riemann solver which
is based on the spectral decomposition of the Jacobian matrices of
relativistic hydrodynamics.
---------------------------------------------------------
Title: Equilibrium structure of self-gravitating Keplerian disks.
Authors: Hashimoto, M.; Eriguchi, Y.; Muller, E.
1995A&A...297..135H Altcode:
We present two-dimensional equilibrium models of realistic,
self-gravitating Keplerian disks of arbitrary thickness surrounding
a gravitating central object (star), which is approximated by a point
mass. The point mass and the disk mass of the computed models are in
solar units (0.6, 0.39), (0.6, 1.4), (1.4, 0.006), (1.4, 0.011), (3.5,
0.29) and (10.0, 0.28), respectively. The configuration consisting
of a central star of 0.6M<SUB>sun</SUB>_ and a surrounding disk of
0.39M<SUB>sun</SUB>_ is similar to that obtained in the two-dimensional
hydrodynamical calculation of Bodenheimer et al. (1991). This shows that
we are able to construct equilibrium disk models, which approximate
quasi-equilibrium evolutionary stages of accretion disks encountered
during proto-star formation. Equilibrium models with a more massive
central object, e.g. the (3.5M<SUB>sun</SUB>_, 0.29M<SUB>sun</SUB>_)
model system, can be considered as describing a black hole surrounded
by a thick disk, i.e. being representative of systems like SS 433.
---------------------------------------------------------
Title: Neutrino-driven Type-II supernova explosions and the role
of convection.
Authors: Janka, H. T.; Mueller, E.
1995PhR...256..135J Altcode:
The role of neutrino heating and convection in the explosions of
Type-II supernovae is reviewed. The neutrino-driven mechanism of
supernova explosions is based upon the fact that high-energetic
neutrinos streaming up from the hotter interior must transfer energy
to the cooler layers adjacent to the nascent neutron star. While this
energy deposition is unavoidable, there is still controversy about the
point whether it is able to drive and power a Type-II supernova event
or not. To investigate this question one-dimensional hydrodynamical
simulations have been performed for the long-time evolution of the
collapsed stellar core after the bounce at nuclear matter density and
after the associated formation of the supernova shock. In these studies
the parameters describing the neutrino emission have been varied and
the influence of the temporal contraction of the central part of the
nascent neutron star has been tested.
---------------------------------------------------------
Title: SN Ia: Light Curves, Spectra,and H<SUB>0</SUB>.
Authors: Höflich, P.; Dominik, C.; Khokhlov, A.; Muller, E.; Wheeler,
J. C.
1995NYASA.759..348H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Instabilitäten und Mischungsvorgänge in Supernovaexplosionen
vom Typ II. Computersimulationen einer kosmischen Katastrophe.
Authors: Müller, E.
1995S&W....34..350M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Neutron star recoils from anisotropic supernovae.
Authors: Janka, H. -T.; Mueller, E.
1994A&A...290..496J Altcode:
Refering to recent hydrodynamical computations (Herant et al. 1992;
Janka & Mueller 1993a) it is argued that neutron star kicks up to a
few hundred km/s might be caused by a turbulent overturn of the matter
between proto-neutron star and supernova shock during the early phase
of the supernova explosion. These recoil speeds ("kick velocities")
may be of the right size to explain the measured proper motions of
most pulsars and do not require the presence of magnetic fields in the
star. It is also possible that anisotropic neutrino emission associated
with convective processes in the surface layers of the nascent neutron
star (Burrows & Fryxell 1992; Janka & Mueller 1993b; Mueller
1993) provides an acceleration mechanism (Woosley 1987), although our
estimates indicate that the maximum attainable velocities are around
200km/s. Yet, it turns out to be very unlikely that the considered
stochastic asymmetries of supernova explosions are able to produce
large enough recoils to account for pulsar velocities in excess of about
500km/s, which can be found in the samples of Harrison et al. (1993) and
Taylor et al. (1993). It is concluded that other acceleration mechanisms
have to be devised to explain the fast motion of PSR 2224+65 (transverse
speed >=800km/s Cordes et al. 1993) and the high-velocities deduced
from associations between supernova remnants and nearby young pulsars
(e.g., Frail & Kulkarni 1991; Stewart et al. 1993; Caraveo 1993).
---------------------------------------------------------
Title: Gamma-Ray Light Curves and Spectra of Models for Type IA
Supernovae
Authors: Hoeflich, P.; Khokhlov, A.; Mueller, E.
1994ApJS...92..501H Altcode:
Based on detailed Monte Carlo calculations, we present γ-ray energy
deposition functions, γ-ray light curves, and γ-ray spectra for
a large set of theoretical models of Type Ia supernovae including
"classical" detonation and deflagration, delayed detonation,
explosions of low mass white dwarfs, and tamped detonation
scenarios. Our computations show that models for Type Ia supernovae
can be discriminated and the absolute amount of ^56^Ni synthesized in
the event can be determined on the basis of the γ-ray light curves
and spectra if γ-ray measurements are combined with observations at
other wavelengths, e.g., in the optical band. We discuss at which times
γ-ray observations are most suitable and needed from the theoretical
point of view. The implication of the upper limit in the γ-ray flux
by CGRO experiment for our understanding of SN 1991T is discussed. We
find that this limit is consistent with both the optical light curve
and the implied distance (12.5 Mpc) i.e., several models can be ruled
out by the γ-ray observations.
---------------------------------------------------------
Title: A comparison of calculated and observed monochromatic type
IA supernova light curves.
Authors: Mueller, E.; Hoeflich, P.
1994A&A...281...51M Altcode:
The calculated monochromatic (B and V) light curves of a set of Type
Ia supernova models are compared with the observed monochromatic
light curves of 13 Type Ia supernovae (SNIa). The set consists of 11
Type Ia supernova models including deflagrations, detonations, delayed
detonations, pulsating delayed detonations and tamped detonations. The
theoretical light curves have been calculated using our recently
developed light curve model. The model incorporates a detailed equation
of state with an elaborate treatment of the ionization balance,
an implicit grey LTE radiation transport scheme based on the moment
equations, a total energy equation for the gas and the radiation field,
expansion opacities, and a Monte Carlo gamma-ray deposition scheme. To
evolve the structure of the underlying explosion models homologous
expansion is assumed. We find that fast rising light curves (e.g.,
SN 1972E, SN 1981B and SN 1986G) can be reproduced best by delayed
detonation models, and that slowly rising (t_max_ >~ 17 days)
light curves (e.g., SN 1984A and SN 1990N) cannot be reproduced by
standard detonation, deflagration or delayed detonation models. In
order to obtain an acceptable agreement with observations for slowly
rising light curves explosion models are required where the C/O white
dwarf is surrounded by an unburnt extended envelope of typically 0.2
to 0.4 M_sun_. Our interpretation of the light curves is also favoured
from the expansion velocities observed in the spectra of the slowly
rising SNIa. Based on a comparison of theoretical light curves and
observational data, the distances of the parent galaxies have been
determined. We show that SNe Ia allow for a measurement of the value of
the Hubble constant provided individual fits are used and if they are
located at distances larger than 15 Mpc, because only then they are
in the "Hubble" flow. Taking this restriction into account a Hubble
constant of H = 66 +/- 10 km/(secMpc) can be derived within a 2σ error.
---------------------------------------------------------
Title: The formation of disk galaxies in a cosmological context:
Populations, metallicities and metallicity gradients
Authors: Steinmetz, M.; Mueller, E.
1994A&A...281L..97S Altcode: 1993astro.ph.12010S
We present first results concerning the metallicities and stellar
populations of galaxies formed in a cosmologically motivated
simulation. The calculations include dark matter, gas dynamics,
radiation processes, star formation, supernovae feed-back, and metal
enrichment. A rotating, overdense sphere with a mass of 8 10^11^ M_sun_
serves as initial model. Converging and Jeans unstable regions are
allowed to form stars, which get their metallicity from the gas they
are formed from. Via supernovae, metal enriched gas is given back to
the interstellar medium. The forming galaxy shows the main properties
of spiral galaxies: A metal rich bulge, a metal poor stellar halo and a
disk of nearly solar composition. Halo and bulge consist predominantly
of old stars (> 10.5 Gyrs). The disk has a metallicity gradient of
d(log Z)/dr = -0.05 kpc^- 1^, whereas the halo shows none. The models
also exhibit a correlation between the metallicity of Pop II stars
and the power of small scale fluctuations. The stars of the bulge
form from gas which is initially located in the largest maxima of the
primordial density fluctuations, whereas the halo stars originate from
gas accumulated in less pronounced maxima.
---------------------------------------------------------
Title: Simulation turbulenter Konvektion in Supernova-Explosionen
massereicher Sterne.
Authors: Janka, H. -T.; Müller, E.; Ruffert, M.
1994stks.book.....J Altcode:
Contents: 1. Das Projekt: Numerische Simulation von
Typ-II-Supernovae. 2. Die numerischen Verfahren. 3. Die Visualisierung
von dreidimensionalen Datensätzen. 4. Die Ergebnisse: Einblick in
explodierende Sterne.
---------------------------------------------------------
Title: Galaxy formation in a cluster environment: first steps to a
consistent description
Authors: Steinmetz, M.; Müller, E.
1994pvgt.conf...34S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Multi-Dimensional Simulations of Neutrino-Driven Supernovae.
Authors: Mueller, E.; Janka, H. -T.
1994RvMA....7..103M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Hydrodynamical simulations of relativistic jets
Authors: Marti, J. M.; Mueller, E.; Ibanez, J. M.
1994A&A...281L...9M Altcode:
We have performed simulations of relativistic pressure-matched slab
jets with beam Lorentz factors in the range 4.1 to 22.4 using a modern
high-resolution shock-capturing technique based on an approximate
relativistic Riemann solver. Our results show that the basic structural
components found in Newtonian simulations, i.e. beam, cocoon, working
surface and bow shock, are also present in relativistic jets. We
further find that the head of the jet propagates at relativistic speed
which depends on the beam velocity in a very non-linear way, and that
relativistic jets seem to be more stable than Newtonian ones. Finally,
our preliminary results strongly support the necessity of a more
detailed study of the morphology and dynamics of relativistic jets.
---------------------------------------------------------
Title: Two- and three-dimensional simulations of convection in
protoneutron stars.
Authors: Müller, E.
1993nuas.symp...27M Altcode:
The author presents some results from hydrodynamical simulations of
supernova explosions, which clearly show the existence of convective
instabilities in the mantle of the collapsing stellar core.
---------------------------------------------------------
Title: Simulations of the evolution of galaxy clusters. II. Dynamics
of the intra-cluster gas.
Authors: Schindler, S.; Muller, E.
1993A&A...272..137S Altcode:
We present simulations of the evolution of galaxy clusters including
both collisionless matter (galaxies and dark matter) and intra-
cluster gas. The simulations have been performed using a direct
N-body integrator for the collisionless component combined with
a finite difference scheme (PPM) for the gas dynamics. With this
combined method we have investigated the collision of subclusters as
well as the subsequent quasi-equilibrium state by calculating several
models with different initial conditions. The collision of subclusters
produces several shock waves of varying strength depending on the
mass of the colliding subclusters. In particular, the collision of
two large subclusters causes a lens-shaped shock front. After merging
the model cluster is not isothermal, but shows a hot central region
(T >= 3 10^8^K) and temporarily cool regions (T <= 5 10^7^K). We
have also calculated the X-ray image of the model cluster when it
would be observed by ROSAT. The collision of large subclusters gives
rise to distorted X-ray contours at the moment of collision and to
lens-shaped contours when the strong shock front resulting from the
collision begins to expand. We have also calculated X-ray temperature
maps which are expected to be observable with the next generation of
X-ray telescopes. We find that these temperature maps show many details
of the collision, e.g., the heated gas between two subclusters shortly
before their collision and the steep temperature gradients at shock
fronts. Thus, the evolutionary state of a cluster can be characterized
much better when these temperature data are available. An investigation
of the so-called β-discrepancy shows no discrepancy in our cluster
models. Our results further show that a frequent occurance of cooling
flows can be one of the reasons for the β-discrepancy.
---------------------------------------------------------
Title: A comparison between SPH and PPM: simulations of stellar
collisions
Authors: Davies, M. B.; Ruffert, M.; Benz, W.; Muller, E.
1993A&A...272..430D Altcode:
A full 3D implementation of the smoothed particle hydrodynamics
method (SPH) is compared to the 3D Eulerian piecewise parabolic
method (P PM). Both codes were used to simulate a collision between a
0.5M<SUB>sun</SUB> main- sequence star (modelled as a n=3/2 polytrope)
and a white dwarf star of equal mass (treated as a point mass). The
encounter was simulated 6 times with SPH (the number of particles
ranging between 2900 and 27000) and twice with PPM (using 64<SUP>3</SUP>
and l28<SUP>3</SUP> cartesian zones). A multiple grid implementation
of the PPM code was also employed (5 nested grids of 32<SUP>3</SUP>
zones each). <P />Our results show that the key factor determining
the overall result of the collision is the form of the potential well
of the point mass. Depending on the exact numerical smoothing of the
well, different trajectories, amounts of mass accretion and maximum
temperatures are obtained. Once both codes are run with the same point
mass potential, the global values (e.g. total energy, angular momentum,
center of mass trajectory, etc.) arc in good agreement. However
the results differ in the values of local quantities like density
distribution in the immediate vicinity of the point mass, and in the
envelope structure. <P />The choice of an impartial test problem is
difficult, since advantages and disadvantages of both methods are
largely mutually exclusive. For the modeling of stellar collisions,
SPH and PPM produce results that compare quite favorably. Hence,
given that both schemes are fundamentally different, we assume that
common features are physical in nature and not numerical.
---------------------------------------------------------
Title: Light curves of type IA supernova models with different
explosion mechanisms.
Authors: Khokhlov, A.; Mueller, E.; Hoeflich, P.
1993A&A...270..223K Altcode:
The deflagration, detonation, delayed detonation, pulsating delayed
detonation, and tamped detonation scenarios for Type Ia SNs are here
addressed by the bolometric, blue, and visual light curves generated
by a set of theoretical models. Several correlations between observable
quantities and model parameters are found which allow for discrimination
between models. Standard and nonstandard models are distinguished by
the time-dependence of the photospheric expansion velocity, which is
directly measurable by the Doppler shift of spectral lines.
---------------------------------------------------------
Title: Self-gravitating and rotating hot toroids
Authors: Hashimoto, M.; Eriguchi, Y.; Arai, K.; Mueller, E.
1993A&A...268..131H Altcode:
We solved structures of self-gravitating toroidal stars, in which
the temperature is high enough for nuclear burnings to occur. For a
pseudobarotropic toroidal star, we found that the maximum temperature
can exceed 10 exp 9 K for some models, although there is a critical
value for it within the toroid beyond which no equilibrium states
exist. The maximum luminosity is found to exceed the Eddington
luminosity considerably. Since the maximum temperature is the key
quantity to judge which kind of nuclear burning can occur, the high
temperature inside toroidal stars suggests the occurrence of significant
amounts of nuclear reactions. Because essential features of toroidal
stars seem to be common to accretion disks, one can also expect the
possibility of appreciable nucleosynthesis inside thick accretion disks.
---------------------------------------------------------
Title: On the capabilities and limits of smoothed particle
hydrodynamics
Authors: Steinmetz, M.; Mueller, E.
1993A&A...268..391S Altcode:
The capabilities and limits of smoothed particle hydrodynamics
(SPH) are discussed, emphasizing the problems arising in SPH when a
variable smoothing length is used and when an initial model is to be
constructed. A new approach to solve the variable smoothing length
problem is described which allows a more stable time integration
without additional computing time. The approach is implemented
into a new SPH code which uses a hierarchical binary tree method to
handle self-gravity. The capabilities and limits of the SPH method are
illustrated with a set of problems. Results for oscillating polytropes
show that with the new approach the intrinsic numerical diffusion of
the SPH method can be drastically reduced to much less than that of
most multidimensional Eulerian and Lagrangian schemes.
---------------------------------------------------------
Title: Light curve models for type IA supernovae - Physical
assumptions, their influence and validity
Authors: Hoeflich, P.; Mueller, E.; Khokhlov, A.
1993A&A...268..570H Altcode:
A state of the art radiation transfer code is presented for computing
bolometric and monochromatic light curves of Type Ia supernovae. The
radiation transfer code, which is also applicable to Type II supernovae,
consists of (i) a LTE radiation transfer scheme (including an energy
equation for matter and radiation, and effects due to electron and
line scattering) based on the time-dependent, frequency integrated
moment equations which are solved implicitly, (ii) a detailed equation
of state with an elaborate treatment of the ionization balance and
the ionization energies, (iii) time-dependent expansion opacities
which take into account the composition structure of the explosion
model, and (iv) a Monte Carlo gamma-ray deposition scheme which
takes into account all relevant gamma-ray transitions and interaction
processes. concerning the evolution of the structure of the explosion
model a homologous expansion of the ejecta is assumed. The opacities
are calculated under the assumption that temperature, density, chemical
composition and expansion rate are constant over the free mean path of a
photon. The mean expansion opacity which is obtained from the calculated
monochromatic expansion opacities both by a Rosseland and a Planck mean,
is given in tabular form. We find that the Rosseland and Planck mean
opacity can differ by more than an order of magnitude. Each opacity
table contains the mean expansion opacity as a function of temperature
density and expansion rate for a prescribed composition. In the light
curve calculations interpolations have to be performed between different
tables corresponding to chemically different layers of the ejecta. Using
our radiation transfer code we have calculated the bolometric and
monochromatic light curves of a particular delayed detonation model
(N21). The calculations have also been performed assuming various
levels of physical simplifications (e.g. constant opacity diffusion
approximation- no scattering) in order to study the influence and
validity of many commonly made physical assumptions in modelling Type
Ia supernova light curves. According to our results the temperature
structure of the envelope critically depends on the use of a time-
dependent opacity, the inclusion of line scattering, the correct;
distinction between the frequency averaging in the radiation energy
(Planck mean) and radiation flux (Rosseland mean) moment equations, and
on the approximations used in the radiation transfer. In particular,
the coupling between temperature profile and optical depth cannot be
neglected, e.g., as done when assuming a constant opacity. Consequently,
the time-dependent photospheric radius is strongly affected by the
assumptions and approximations made in a light curve model. At maximum
light the photospheric radius can be wrong by up to 70% with the error;
increasing at later epochs. This fact can have important implications
for Type Ia supernovae both for their use as distance indicators via the
Baade-Wesselink method, and for their spectral analysis. Our results
further show that although the bolometric light curve only depends on
the total energy deposition due to the decay of ^56^Co at late epochs,
its early rise, its maximum luminosity L_bol_, the time of maximum light
t_bol_(max), and its early decline sensitively depend on the physical
assumptions. In particular, using a time-independent opacity may cause
an error in L_bol_(max) of about 50% and in t_bol_(max) of about 3.5
days, respectively. In order to obtain accurate monochromatic light
curves line scattering effects must be taken into account, because
otherwise most of the flux will erroneously be emitted in the infrared.
---------------------------------------------------------
Title: Galaxy formation in a cluster environment: first steps to a
consistent description.
Authors: Steinmetz, M.; Müller, E.
1993AGAb....8...16S Altcode: 1993AGAb....8...16.
No abstract at ADS
---------------------------------------------------------
Title: Gamma-ray light curves and spectra for SN IA
Authors: Hoeflich, P.; Mueller, E.; Khokhlov, A.
1993A&AS...97..221H Altcode:
Based on detailed Monte Carlo calculations, we present gamma-ray energy
deposition functions, gamma-ray light curves and gamma-ray spectra for
a large set of theoretical models of Type Ia supernovae. They include
'classical' detonation and deflagration models, recently proposed
delayed detonation models, and tamped detonation models, which may
crudely resemble merger or common envelope configurations.
---------------------------------------------------------
Title: Nucleosynthesis in type Ia supernovae: effects of non-spherical
detonations
Authors: Steinmetz, M.; Müller, E.
1993nuco.conf..563S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Gravitational radiation from the collapse of rotating stellar
cores.
Authors: Schäfer, G.; Mönchmeyer, R.; Müller, E.
1993rges.conf..278S Altcode: 1993rges.rept..278S
The authors present gravitational waveforms derived from data of
four numerical model calculations of axisymmetric collapse processes
in rotating 1.36 M<SUB>sun</SUB> stellar iron cores. The maximal
amplitudes (at a distance of 10 Mpc) range from 4×10<SUP>-24</SUP>
to 2×10<SUP>-23</SUP>, the frequencies at maximum spectral energy
density have values of 100 Hz - 700 Hz and the radiated energy is in
the range (0.2 - 8.0)×10<SUP>-8</SUP>M<SUB>sun</SUB>c<SUP>2</SUP>. In
comparison to previous calculations the obtained waveforms show standard
and non-standard features.
---------------------------------------------------------
Title: Neutrino-driven type-II supernovae: neutrino heating and post
bounce dynamics.
Authors: Janka, H. -T.; Müller, E.
1993fna..conf..203J Altcode:
The currently most promising model to explain the explosion
of massive stars (8 M<SUB><SUB>sun</SUB></SUB> ⪉ M ⪉ 25
M<SUB><SUB>sun</SUB></SUB>) in type-II supernovae is the "delayed
mechanism" by neutrino heating. A small fraction of the order of one
per cent of the total energy carried away from the collapsed stellar
core in form of neutrinos, several 10<SUP>53</SUP>erg, is thought to
be transferred to the material outside and close to the newly formed
protoneutron star. This energy causes a huge expansion, by which
an extended region of low density, but quite high temperature, is
created above the surface of the young neutron star. The persistent
energy input by neutrinos maintains high pressure in this region,
thus driving the supernova shock into the stellar mantle and reversing
the star's infall to an explosion. In this work the dynamics of such
a scenario are investigated by numerical simulations of the formation
and evolution of the hot bubble region around the newly born neutron
star in one dimension. The equation of state of the stellar gas as
well as the interactions between neutrinos and the gas particles
are described with a high degree of accuracy. These simulations show
that the explosion energy stays too low, i.e. of the order of a few
10<SUP>50</SUP>erg instead of the expected 1 - 1.5×10<SUP>51</SUP>erg
for a typical type-II supernova explosion, unless one "adds" a mechanism
of efficient neutrino heating during the early phase (⪉1 second)
of the post-bounce evolution. This strongly indicates the lack of
important physics in spherically symmetric simulations. The authors show
first results of hydrodynamical simulations in two dimensions to study
possible effects of convection inside the newly formed neutron star
and between the compact remnant and the outward moving supernova shock.
---------------------------------------------------------
Title: A comparison of calculated and observed monochromatic type
IA supernova light curves
Authors: Mueller, E.; Hoeflich, P.
1992STIN...9417629M Altcode:
The calculated monochromatic light curves of a set of type Ia supernova
models are compared with the observed monochromatic light curves of 13
type Ia Supernovae (SNIa). The set consists of 11 type Ia supernova
models including deflagrations, detonations, delayed detonations,
pulsating delayed detonations and tamped detonations. The theoretical
light curves were calculated using our recently developed light curve
model. The model incorporates a detailed equation of state with an
elaborate treatment of the ionization balance, an implicit grey LTE
(Local Thermodynamic Equilibrium) radiation transport scheme based
on the moment equations, a total energy equation for the gas and the
radiation field, expansion opacities, and a Monte Carlo gamma ray
deposition scheme. To evolve the structure of the underlying explosion
models homologous expansion is assumed. Based on a comparison of
theoretical light curves and observational data, the distances of the
patent galaxies were determined. It is shown that SNe Ia allow for a
measurement of the value of the Hubble constant provided individual
fits are used and if they are located at distances larger than 15 Mpc,
because only then they are in the 'Hubble' flow. Taking this restriction
into account a Hubble constant can be derived within a 2 sigma error.
---------------------------------------------------------
Title: Gamma-ray light curves and spectra for Type IA supernovae
Authors: Hoeflich, P.; Khokhlov, A.; Mueller, E.
1992A&A...259..549H Altcode:
The gamma-ray energy deposition functions, light curves, and spectra
have been computed for a set of theoretical Type Ia supernova models
including deflagration, detonation, delayed detonation, and tamped
detonation models. The results have been obtained with a Monte Carlo
gamma-ray deposition scheme that takes all relevant gamma transitions
and interaction processes into account. The computations demonstrate
that Type Ia supernova models can be discriminated and that the absolute
amount of Ni-56 synthesized in the event can be determined from the
gamma-ray light curves and spectra.
---------------------------------------------------------
Title: Carbon Detonations in Rapidly Rotating White Dwarfs
Authors: Steinmetz, M.; Muller, E.; Hillebrandt, W.
1992A&A...254..177S Altcode:
We have performed a set of two-dimensional hydrodynamic
simulations of the propagation of detonation waves in rapidly
rotating white dwarfs. The axisymmetric initial models used in the
simulations are in rotational equilibrium and possess a density
stratification similar to that of configurations predicted by
the merging scenario of Type Ia supernovae. The energy release
is approximated by a single exothermic nuclear reaction 14
<SUP>12</SUP>C → 3 <SUP>56</SUP>Ni proceeding at the rate of
the <SUP>12</SUP>C(<SUP>12</SUP>C,<SUP>4</SUP>He)<SUP>20</SUP>Ne
reaction. Central and off-center ignitions have been studied. <P />When
burning is ignited in the center our results show, that independently
of the shape of the star, all matter is burned into iron group
elements and the star is completely disrupted after typically 200
msec. Igniting the white dwarf in an extended central region having a
more or less flattened spheroidal or cylindrical shape gives rise to an
initially different behaviour, but within about 100 msec the shape of
the detonation wave approaches that of one being ignited only in the
center. When burning is ignited off-center all carbon is consumed,
too. Thus detonations in non-spherical massive white dwarfs cannot
explain the observed intermediate mass elements seen in the spectra
of Type Ia supernovae.
---------------------------------------------------------
Title: Gravitational waves from supernova explosions.
Authors: Müller, E.; Mönchmeyer, R.; Schäfer, G.
1992AGAb....7...57M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Hydrodynamical cosmology: galaxy formation in a cosmological
context.
Authors: Steinmetz, M.; Müller, E.
1992AGAb....7...15S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Type IA supernovae : theoretical light curves with a slow
pre-maximum rise.
Authors: Khokhlov, A.; Mueller, E.; Hoeflich, P.
1992A&A...253L...9K Altcode:
We present theoretical light curve (LC) calculations which reproduce
Type Ia supernovae with a slow pre-maximum rise (V maximum at ~ 20
days), like the recently observed SN 1990 N. We use the same input
physics as in our previous work (Hoflich et al. 1991). In addition,
both Thomson and line scattering has been included, which is crucial
for reproducing the monochromatic LC. For the radiation transport the
moment equations are solved. Our calculations are based on delayed
detonation models in which the transition from a deflagration to a
detonation occurs due to the pulsation of an exploding white dwarf. The
interaction with an extended low density envelope created during the
pulsation leads to a substantial redistribution of the kinetic energy
inside the ejecta. The deceleration of the bulk of matter to <~
10000 km/sec delays the rise time of the light curve from ~ 10 -
12 days, typical of delayed detonation models without a pulsation,
to ~ 17 days, whereas the outer envelope acquires velocities of up to
30000 km/sec. The interaction with the extended ~10^10^ cm envelope
is not specific to the delayed detonation scenario. To illustrate the
effect we present the results of computations of the explosion of 1.2
M_sun_CO-WD inside an extended envelope of 0.8 M_sun_, which results
in a rise time of ~ 25 days.
---------------------------------------------------------
Title: Instability and clumping in SN 1987A.
Authors: Mueller, E.; Fryxell, B.; Arnett, D.
1991A&A...251..505M Altcode:
Two-dimensional hydrodynamic calculations of Rayleigh-Taylor
instabilities in the ejecta of SN1987A are described. These calculations
covering the first few hours of the evolution were performed on a grid
of 1000^2^, which provides significantly better resolution than obtained
in previous calculations (Fryxell et al. 1991). As a result of the
improved resolution, two new regions of instability were discovered. In
addition, the structure of the Rayleigh-Taylor fingers became much more
complex. The numerical experiment was found to be consistent with a
linear stability analysis. In addition, we compare the two-dimensional
results to the results of a one-dimensional calculation to show the
effects of the nonspherical motion on the structure and composition
distribution of the ejecta.
---------------------------------------------------------
Title: Multi-Dimensional Calculations of Instabilities in Supernova
Explosions
Authors: Fryxell, B. A.; Müller, E.; Arnett, D.; Ruffert, M.
1991BAAS...23.1407F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Type IA supernovae : gamma-rays as predicted by delayed
detonation modelsand SN 1991T.
Authors: Mueller, E.; Hoeflich, P.; Khokhlov, A.
1991A&A...249L...1M Altcode:
We have computed the γ-ray spectra for two delayed detonation
models of Khokhlov (1991a, b). The results have been obtained with
a Monte Carlo γ-ray deposition scheme being part of our detailed
supernova light curve model. For a source located at a distance of
10 Mpc the delayed detonation model, which best fits observed light
curves of "fast" type Ia supernovae and is capable to reproduce their
spectra, predicts a γ-ray flux for the ^56^Co line at 847 keV easily
detectable by COMPTEL. Our computations also strongly indicate that
SN Ia models can be discriminated on the basis of early time γ-ray
observations. Concerning the recently discovered type Ia supernova
SN 1991T the delayed detonation model predicts a γ-ray flux for the
847 keV line of 1.0 10^-3^ photons s^-1^ cm^-2^ MeV^-1^ for day 81
(i.e., June 23, 1991 for SN 1991T), and of 3.8 10^-4^ photons s^-1^
cm^-2^ MeV^-1^ for day 190 (i.e., October 10, 1991 for SN 1991T). The
theoretical spectra have been folded with the energy response function
which gives rise to a significant modification of the original
spectra. The number of photons predicted for the 847 keV line for an
integration time of 5 10^5^ s are about 310 at day 81 and 150 at day
190, respectively.
---------------------------------------------------------
Title: Structure of rapidly rotating axisymmetric stars. I - A
numerical method for stellar structure and meridional circulation
Authors: Eriguchi, Y.; Mueller, E.
1991A&A...248..435E Altcode:
A numerical method is presented for calculating the mechanical and
thermal structure of stationary axisymmetric inviscid rotating stars in
which the velocity of the meridional flow is very slow. The structure
of the rotating configuration is computed and the flow pattern for the
given configuration is calculated. Several sequences of stationary
configurations for three different rotation laws are computed. For
the energy generation, the point source model is assumed and two
kinds of opacities (electron scattering opacity and Kramers opacity)
are examined. A two-zone flow pattern is found in the uniformly
rotating models. Models with two kinds of differential rotation laws
are investigated. The flow patterns in these differentially rotating
models are found to be quite different from those of the uniformly
rotating models. Specifically, near the rotation axis, the flow rising
from the convective core directly reaches the surface of the star.
---------------------------------------------------------
Title: Type IA supernovae : theoretical light curves for SN 1972E
and SN 1981B.
Authors: Hoeflich, P.; Mueller, E.; Khokhlov, A.
1991A&A...248L...7H Altcode:
Based on delayed detonation models of Khokhlov (1991a,b) theoretical
light curves have been calculated, which accurately reproduce the
observed light curves of the Type Ia supernovae SN 1972E and SN
1981B. Our models describe very well both the pre-maximum rise and
the post-maximum decline of the light curve and also give the correct
maximum luminosity. The theoretical light curves are calculated using
(i) a detailed equation of state with an elaborate treatment of the
ionization balance, (ii) an implicit LTE radiation transport scheme
based on a modified diffusion approximation with space and time
dependent correction factors determined by the exact solution of the
radiation transport equation at low optical depths (τ <~ 100),
(iii) tabulated time- dependent expansion opacities which take into
account the composition structure of the initial model,(iv) a Monte
Carlo γ-ray deposition scheme, and (v) homologous expansion to evolve
the structure of the models.
---------------------------------------------------------
Title: New orbits for WDS 02231+7021, WDS 05373+6642, WDS 06425+6612
WDS 22356+5413.
Authors: Muller
1991IAUDS.114....1M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Gravitational waves from the collapse of rotating stellar
cores.
Authors: Moenchmeyer, R.; Schaefer, G.; Mueller, E.; Kates, R. E.
1991A&A...246..417M Altcode:
The paper presents calculations of the gravitational quadrupole,
octupole, and hexadecapole waves resulting from four different numerical
axisymmetric iron core collapse models for rotating 1.36 solar-mass iron
cores of 20 solar-mass stars. A recently derived analytic expression was
used to determine the waveforms. The four resulting waveforms obtained
show qualitatively and quantitatively different shapes, characteristic
of the abundance mechanisms of the models. The dimensionless amplitudes
range up to 2 x 10 to the -23 at a distance of 10 Mpc with the maximum
of the power spectrum in the frequency range 500-1000 Hz. For the most
efficient model, the radiated energy is calculated to be equal to 8
x 10 to the -8th solar mass times c-squared.
---------------------------------------------------------
Title: Nuclear astrophysics. Proceedings.
Authors: Hillebrandt, W.; Müller, E.
1991nap..book.....H Altcode:
Contents: 1. Nuclear properties and reactions of relevance to
astrophysics. 2. s-process nucleosynthesis studies. 3. Stellar
evolution, nucleosynthesis, and abundances in stars. 4. Supernovae and
supernova nucleosynthesis. 5. Chemical evolution of globular clusters
and galaxies.
---------------------------------------------------------
Title: High Resolution Numerical Simulations of Instabilities,
Mixing, and Clumping in Supernova 1987A
Authors: Müller, E.; Fryxell, B.; Arnett, D.
1991ESOC...37...99M Altcode: 1991sos..conf...99M
No abstract at ADS
---------------------------------------------------------
Title: Influence of Time Dependent Opacities on Light Curves of Type
II Supernovae
Authors: Müller, E.; Höflich, P.
1991ESOC...37..379M Altcode: 1991sos..conf..379M
No abstract at ADS
---------------------------------------------------------
Title: Supernovae that are not Spheres
Authors: Arnett, D.; Fryxell, B.; Müller, E.
1991ESOC...37..117A Altcode: 1991sos..conf..117A
No abstract at ADS
---------------------------------------------------------
Title: Instabilities and Mixing in Supernova 1987A
Authors: Arnett, D.; Fryxell, B.; Muller, E.
1991supe.conf..232A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: TOPICAL REVIEW: Supernova theory and the nuclear equation
of state
Authors: Muller, E.
1990JPhG...16.1571M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Three-dimensional hydrodynamical simulations of off-centre
collisions between a white dwarf and a main-sequence star
Authors: Ruffert, M.; Mueller, E.
1990A&A...238..116R Altcode:
A finite difference code based on the piecewise parabolic method is
used here to study off-center collisions between an 0.5 solar mass
main-sequence star (MSS) modeled by a polytrope index of 1.5 and an 0.5
solar mass white dwarf (WD) modeled by a point-mass potential. At small
impact parameters, the MSS is totally disrupted, its matter eventually
settling around the WD, while for large impact parameters the MSS is
only slightly elongated. The amount of mass becoming unbound due to the
collision is estimated to be roughly 15 percent. The expansion of the
shock-heated gas is spherically symmetric. The maximum temperatures
reached during the collision are so low that the nuclear energy
production is negligible.
---------------------------------------------------------
Title: Thermal instabilities in cooling flows - The evolution of
nearly spherical perturbations
Authors: Brinkmann, W.; Mueller, E.; Massaglia, S.
1990A&A...237..536B Altcode:
Numerically, in one and two dimensions, the temporal evolution of
thermally unstable blobs is presently followed in connection with the
problem of mass accretion in cooling flows. The hydrodynamic equations
are solved in spherical geometry for an initially homogeneous cooling
medium, including thermal conduction. The initial isobaric perturbations
are followed in time until self gravity effects, not included in the
equations, are thought to become important. In the one-dimensional
case, after the linear phase the perturbation evolves on time scales
much shorter than the linear ones, and depending on the initial matter
density, a cool, dense core of size about 0.001-0.01 times the initial
perturbation scale size forms. This grows in size due to continuous
accretion from the (hotter) outside gas and may become eventually
gravitationally unstable.
---------------------------------------------------------
Title: Numerical simulations of axially symmetric magnetized jets. I
- The influence of equipartition magnetic fields. II - Apparent
field structure and theoretical radio maps. III - Collimation of
underexpanded jets by magnetic fields
Authors: Koessl, D.; Mueller, E.; Hillebrandt, W.
1990A&A...229..378K Altcode:
The results of a numerical MHD model are discussed, which we have
used to investigate the influence of equipartition magnetic fields on
the propagation of supersonic jets. We find that a purely poloidal
equipartition field is capable of decollimating the jet, whereas a
purely toroidal equipartition field increases the confinement, but
introduces pinching waves. These oscillations can be stabilized by an
additional poloidal field without destroying the collimation.
---------------------------------------------------------
Title: Numerical Simulations of Axially Symmetric Magnetized Jets -
Part Three - Collimation of Underexpanded Jets by Magnetic Fields
Authors: Kossl, D.; Muller, E.; Hillebrandt, W.
1990A&A...229..401K Altcode:
Using a finite difference scheme based on the FCT-algorithm, we have
performed a set of hydrodynamic and magnetohydrodynamic simulations
to investigate the stability of both magnetized and unmagnetized
underexpanded (ζ_H_ = 10) jets. We find that unmagnetized jets with
a fairly high Mach number (Ma_B_ = 6) are stable; low Mach number jets
(Ma_B_ <~ 2), on the other hand, exhibit prominent instabilities. A
toroidal magnetic fie1d of approximately equipartition field strength
is capable of stabilizing these instabilities due to the pinch
effect. However, it changes the morphology of the jet completely by
generating a nose cone. The influence of an additional poloidal magnetic
field, with a field strength comparable to the fie1d strength of the
toroidal component, is small. Its main effect is that it forces part
of the nose cone into a sonic rotation.
---------------------------------------------------------
Title: Numerical Simulations of Axially Symmetric Magnetized Jets -
Part Two - Apparent Field Structure and Theoretical Radio Maps
Authors: Kossl, D.; Muller, E.; Hillebrandt, W.
1990A&A...229..397K Altcode:
The results of numerical MHD models are used to compute apparent field
configurations and theoretical radio maps of extragalactic jets. We
find that the apparent field structure of weak (FR I) radio sources is
readily explained by the projection of the true field configuration
onto a plane perpendicular to the line of sight. Furtheron it is
demonstrated that it is unlikely that the X-like shock structures,
which are found in almost any numerical simulation of supersonic jets,
produce the prominent knots observed in the jets of edge-darkened
extragalactic radio sources.
---------------------------------------------------------
Title: Thermal instabilities in cooling flows: The evolution of
nearly spherical perturbations
Authors: Brinkmann, W.; Massaglia, S.; Mueller, E.
1990STIN...9119365B Altcode:
The temporal evolution of thermally unstable blobs in connection with
the problem of mass accretion in cooling flows is studied numerically,
in one and two dimensions. The hydrodynamic equations are solved
in spherical geometry for an initially homogeneous cooling medium,
including thermal conduction. The initial isobaric perturbations
are followed in time until self gravity effects, not included in the
equations, are thought to become important. In the one dimensional case,
it is found that after the linear phase the perturbation evolves on time
scales much shorter than the linear ones and depending on the initial
matter density, a cool, dense core of size approximately 0.001 - 0.01
times the initial perturbation scale size forms. This grows in size due
to continuous accretion from the (hotter) outside gas and may become
eventually gravitationally unstable. The one dimensional results are
compared with others obtained for a plane-parallel slab geometry. The
qualitative difference between a one dimensional and a two dimensional
calculation with otherwise very similar physical parameters is shown.
---------------------------------------------------------
Title: Carbon detonation in differentially rotating, highly deformed
white dwarfs.
Authors: Steinmetz, M.; Hillebrandt, W.; Müller, E.
1990AGAb....5...14S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Computations of multi-dimensional flows with non-uniform
composition
Authors: Fryxell, B.; Müller, E.; Arnett, D.
1990nuas.symp..100F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Mixing due to Rayleigh-Taylor instabilities in SN 1987A
Authors: Müller, E.; Hillebrandt, W.; Orio, M.; Höflich, P.;
Mönchmeyer, R.; Arnett, D.; Fryxell, B.
1990nuas.symp..103M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Instabilities and Mixing in Supernova 1987A
Authors: Fryxell, B. A.; Arnett, W. D.; Müller, E.
1989BAAS...21.1209F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Mixing and fragmentation in supernova envelopes.
Authors: Muller, E.; Hillebrandt, W.; Orio, M.; Hoflich, P.;
Monchmeyer, R.; Fryxell, B. A.
1989A&A...220..167M Altcode:
The possibility that a Rayleigh-Taylor instability may lead to an early
fragmentation of a supernova shell is investigated by means of 1-, 2-,
and 3-dimensional hydrodynamic simulations. In particular, a 'point
' explosion in a n = 3 polytrope is considered, but, in contrast to
recent simulations with smoothed particle hydrodynamics, no evidence
was found for fragmentation of the shell. These results are in accord
with analytic considerations.
---------------------------------------------------------
Title: A Conservative Second-Order Difference Scheme for Curvilinear
Coordinates - Part One - Assignment of Variables on a Staggered Grid
Authors: Monchmeyer, R.; Muller, E.
1989A&A...217..351M Altcode:
A conservative second-order difference scheme for solving the equations
of ideal hydrodynamics is described. Although it is capable of dealing
with general orthogonal curvilinear coordinates, it was mainly
developed for calculating the axisymmetric collapse of rotating
stellar cores in spherical coordinates. <P />The basic features
of the scheme are: (i) variables are assigned to "volume centers"
of the computational cells and not to "geometrical cell centers" as
usual; (ii) the spatial discretization is of second-order accuracy
and includes monotonicity constraints; (iii) advectional changes are
calculated by using a "volume advection scheme" instead of evaluating
interface integrals of the advection fluxes; (iv) the time evolution
is described by an explicit, second-order accurate discretization (v)
a moving non-equidistant, staggered grid can be used. In addition a
Poisson solver for axially symmetric mass distributions is incorporated
into the scheme. <P />In this paper it is demonstrated that for the
simple but important test problem of a spherical dust collapse the
proposed difference scheme avoids the pitfalls occurring whenever a
discretization scheme originally developed for straight coordinates
is applied to curvilinear Eulerian coordinates in a straightforward way.
---------------------------------------------------------
Title: Hydrodynamics of the interstellar gas in colliding
galaxies. II. Non-central collisions.
Authors: Mueller, E.; Mair, G.; Hillebrandt, W.
1989A&A...216...19M Altcode:
The dynamical and thermal evolution of the warm component of the
interstellar medium during a fast non-central collision of two
galaxies is investigated by means of 3-dimensional hydrodynamic
simulations using a non-equidistant Cartesian grid of up to 10^6^
grid points. The dynamics of the stellar component of the galaxies is
not followed in detail, but its influence on the gas is incorporated
into the model through its gravitational potential, which is assumed
to be of fixed shape. The collision of the galaxies is simulated by
a constant relative motion of the two potential wells, which contain
the isothermal interstellar gas in hydrostatic equilibrium. Radiative
losses of the gas are calculated with the aid of cooling function, and
the self-gravity of the gas component is neglected. We have performed
four simulations varying the relative velocity, the impact parameter
and the number of grid points, respectively. We find that the amount
of matter leaving the galaxies in form of hot gas in case of a large
relative velocity (2 10^3^ km s^-1^) is roughly proportional to the
cross-sectional volume of the two galaxies, which is equal to the total
volume in case of a head-on collision. Comparing the results of two
collisions where the impact parameter was the same but the relative
velocity differed by a factor of two we find that the gas forms a cool
dense ρ > 10^24^ g cm^-3^) disk-like, probably gravitationally
bound object torn apart between the withdrawing galaxies.
---------------------------------------------------------
Title: Proceedings of the 5th Workshop on Nuclear Astrophysics.
Authors: Hillebrandt, W.; Müller, E.
1989nuas.proc.....H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Computation of multi-dimensional flows with non-uniform
composition.
Authors: Fryxell, B.; Müller, E.; Arnett, D.
1989nuas.conf..100F Altcode:
Many astrophysical objects display complex multi-dimensional
behavior. In order to fully understand many of these objects, it is
necessary to compute flows of gas which are made up of an arbitrary
mixture of nuclear species. There are at least two types of situations
where following abundance changes is crucial. One is in the propagation
of detonation and deflagration fronts such as those occurring in
supernovae, novae, X-ray bursts, gamma-ray bursts, and shell flashes
in stars. Here, the nuclear energy released by the propagation of the
burning front is directly related to the composition of the material
ahead of the front. A second important class of calculations involves
determing the amount of mixing of nuclear species which occurs in
stars. This paper describes the development of a numerical code for
studying these processes.
---------------------------------------------------------
Title: Mixing due to Rayleigh-Taylor instabilities in SN 1987A.
Authors: Müller, E.; Hillebrandt, W.; Orio, M.; Höflich, P.;
Mönchmeyer, R.; Arnett, D.; Fryxell, B.
1989nuas.conf..103M Altcode:
The early discovery of soft and hard X-rays as well as of γ-ray line
emission from supernova 1987A indicates that radioactive <SUP>56</SUP>Co
has been mixed from the deep interior of the exploding star into the
hydrogen-rich envelope. This paper reports numerical simulations of
the mixing process by modeling the supernova explosion using a 3-d
explicit Eulerian hydrodynamic code.
---------------------------------------------------------
Title: Models of head-on collisions between a white dwarf and a
low-mass main sequence star
Authors: Rozyczka, M.; Yorke, H. W.; Bodenheimer, P.; Mueller, E.;
Hashimoto, M.
1989A&A...208...69R Altcode:
Two-dimensional axisymmetric hydrodynamical calculations are performed
to simulate the collision of a white dwarf of 0.5 solar mass with
main sequence stars of 0.5 and 1.0 solar masses. A substantial amount
of the main sequence star is dissipated in the collision; however
the amount is dependent on its mass and on the initial velocity of
the white dwarf. Although nuclear reactions were not included in the
hydrodynamic calculations, detailed estimates of reaction rates, based
upon the numerical results, indicate that shock heating is the dominant
mechanism causing dissipation. The precise role of nuclear energy is
not determined because of uncertainties arising from the approximations
and the finite grid. In all calculated cases the amount of material
captured by the white dwarf is sufficient so that it subsequently will
evolve into a red giant.
---------------------------------------------------------
Title: Core collapse with rotation and neutron star formation
Authors: Mönchmeyer, R.; Müller, E.
1989ASIC..262..549M Altcode:
Numerical simulations of the collapse of non-rotating and rotating
cores of massive stars (M ≥ 8 M<SUB><SUB>sun</SUB></SUB>)
are presented. After reviewing briefly the underlying physics the
numerical results are discussed and possible consequences for neutron
star formation are outlined.
---------------------------------------------------------
Title: Book Review: Nuclear astrophysics. / Springer, 1987
Authors: Kuhfuss, R.; Muller, E.; Truran, J. W.; Doom, C.
1989SSRv...51R.425H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Constraints on the Nuclear Equation of State from Type II
Supernovae and Newly Born Neutron Stars
Authors: Hillebrandt, W.; Müller, E.; Monchmeyer, R.
1989ASIB..216..689H Altcode: 1989nesa.confA.689H
No abstract at ADS
---------------------------------------------------------
Title: Numerical simulations of astrophysical jets: the influence
of boundary conditions and grid resolution.
Authors: Koessl, D.; Mueller, E.
1988A&A...206..204K Altcode:
A new type of flux-corrected-transport (FCT) algorithm is
described. Test calculations show that the new algorithm is superior
to earlier FCT-versions. The algorithm is used to investigate
the influence of boundary conditions and grid resolution on the
simulation of supersonic jet propagation. We find that the solution
is sensitive to the upwind boundary condition even in late stages of
the jet evolution. Furthermore it is demonstrated that a converged
solution cannot be obtained with the grid resolution which has been
assumed to be sufficient in other simulations. Limitations arising in
any jet simulation when trying to compare the numerical results with
observations are pointed out.
---------------------------------------------------------
Title: Density functional calculations in strong magnetic fields -
The ground state properties of atoms
Authors: Koessl, D.; Wolff, R. G.; Mueller, E.; Hillebrandt, W.
1988A&A...205..347K Altcode:
The ground state binding energy, the ionisation energy, the electron
density distribution and the quadrupole moment of iron atoms in strong
magnetic fields (1 - 8×10<SUP>12</SUP>G) have been calculated using the
density functional method. The authors have also performed calculations
of the ground state energy for helium, carbon, and oxygen atoms, and for
the helium-like ions of carbon (C<SUP>4+</SUP>), oxygen (O<SUP>6+</SUP>)
and iron (Fe<SUP>24</SUP>+), respectively. Finally, they have calculated
the binding energy (per atom) of a hexagonal iron crystal due to the
quadrupole-quadrupole interaction of the deformed iron atoms.
---------------------------------------------------------
Title: Book Review: Nuclear astrophysics. / Springer, 1987
Authors: Kuhfuss, R.; Muller, E.; Truran, J. W.; Tayler, R. J.
1988Obs...108..187H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Hydrodynamics of the interstellar gas in colliding galaxies
Authors: Mair, G.; Mueller, E.; Hillebrandt, W.; Arnold, C. N.
1988A&A...199..114M Altcode:
The dynamical and thermal evolution of the warm component of the
interstellar medium during a fast head-on collision of two galaxies is
investigated by means of two-dimensional hydrodynamic simulations. The
dynamics of the stellar component of the galaxies is not followed
in detail, but its influence on the gas is incorporated into the
model through its gravitational potential which is assumed to be of
fixed shape. The collision of the galaxies is simulated by a constant
relative motion of the two potential wells, which contain the isothermal
interstellar gas in the hydrostatic equilibrium. Radiative losses of
the gas are calculated with the aid of a cooling function, and the
self-gravity of the gas component is neglected. In the given parameter
space of relative velocity, escape velocity and chemical composition
of the interstellar matter the total gas content of the colliding
galaxies is swept out. In the case of a large relative velocity (2
10^3^ km s^-1^) the matter is leaving the galaxies in form of hot gas,
while for a smaller relative velocity (10^3^ km s^-1^) the gas forms
a cool disk-like, probably gravitationally bound object between the
withdrawing galaxies.
---------------------------------------------------------
Title: Book-Review - Nuclear Astrophysics - LECTURE-NOTES/PHYSICS:287
Authors: Hillebrandt, W.; Kuhfuss, R.; Muller, E.; Truran, J.
1988JBAA...98..140H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Book-Review - Nuclear Astrophysics
Authors: Hillebrandt, W.; Kuhfuss, R.; Muller, E.; Truran, J. W.
1988S&T....75Q.161H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Report of IAU Commission 38: Exchange of astronomers (Echange
des astronomes).
Authors: Müller, E. A.
1988IAUTA..20..537M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Reminiscences: Zürich, 1948: first post-WWII General Assembly.
Authors: Müller, E. A.
1988itod....4....4M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Size Dependence of Surface Thermodynamic Parameters of
Microclusters and the Location of the Gibbs' " Surface of Tension"
Authors: Müller, E.; Vogelsberger, W.; Fritsche, H. -G.
1988LNP...309..442M Altcode: 1988aan..conf..442M
No abstract at ADS
---------------------------------------------------------
Title: Indications for black hole formation from neutrino observations
in SN1987a.
Authors: Hillebrandt, W.; Hoflich, P.; Kafka, P.; Muller, E.; Schmidt,
H. U.; Truran, J. W.
1987A&A...180L..20H Altcode:
Neutrinos detected by both the KAMIOKA and IMB experiments, five hours
after the neutrino pulse seen in the Mont Blanc experiment, indicate
that the neutron star formed in the supernova SN 1987A in the LMC may
have collapsed further to a black hole. Since this should have happened
within less than a second, the KAMIOKA-data suggest the arrival of two
distinct groups of neutrinos with different rest masses. The six events
arriving during the first second can be fitted by a rest mass of 7.6(+4,
-3) eV/c<SUP>2</SUP>, which would be still consistent with the previous
estimate from the Mont Blanc data (Hillebrandt et al. 1987A). The second
group requires a larger rest mass of 69(+24, -45) eV/c<SUP>2</SUP>.
---------------------------------------------------------
Title: Evidence for a finite electron neutrino rest mass from
SN 1987A.
Authors: Hillebrandt, W.; Hoflich, P.; Kafka, P.; Muller, E.; Schmidt,
H. U.; Truran, J. W.; Wampler, J.
1987A&A...177L..41H Altcode:
The detected neutrino pulse of finite width correlated with the
optical discovery of SN 1987A in the LMC allows the determination of
the neutrino rest mass. Taking into account possible uncertainties in
both the original width of the emitted neutrino pulse and the expected
neutrino energy spectrum from type II supernovae, an electron neutrino
rest mass of 11-23 eV/c sq is derived, in agreement with the recent
limit obtained from decay experiments.
---------------------------------------------------------
Title: Evidence for black hole formation from neutrino observations
in SN 1987a.
Authors: Hillebrandt, W.; Höflich, P.; Kafka, P.; Müller, E.;
Schmidt, H. U.; Truran, J. W.
1987MPARp.278....5H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Computational problems in supernova simulations.
Authors: Müller, E.
1987CoPhC..44..271M Altcode:
Theoretical models of type I and type II supernova explosions are
reviewed from a computational physics point of view. After discussing
briefly the underlying physics the numerical problems and challenges
encountered in the simulation of type I and type II supernova are
addressed.
---------------------------------------------------------
Title: Hydrodynamics of the interstellar gas in colliding
galaxies. I. Head-on collisions.
Authors: Mair, G.; Müller, E.; Hillebrandt, W.; Arnold, C. N.
1987MPARp.314.....M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Evidence for a finite electron neutrino rest mass from
SN 1987a.
Authors: Hillebrandt, W.; Höflich, P.; Kafka, P.; Müller, E.;
Schmidt, H. U.; Truran, J. W.; Wampler, J.
1987MPARp.278....1H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Meridional flow in a self-gravitating body. I. Mechanical
flow in a barotropic star with constant specific angular momentum.
Authors: Eriguchi, Y.; Mueller, E.; Hachisu, I.
1986A&A...168..130E Altcode:
The mechanical part of the equations governing meridional circulation in
a self-graviting body is solved. Stationary axisymmetric solutions are
computed neglecting the effects of viscosity and assuming that the fluid
is incompressible and has a constant specific angular momentum. Then,
the vorticity has a simple relation to the stream function. Three
types of models are investigated: (1) nonrotating configurations of
spherical topology which are deformed due to the internal motion (pure
circulation case); (2) rotating configurations of toroidal topology;
and (3) models consisting of a rotating toroidal configuration and a
central point mass (accretion disk case). Assuming appropriate choices
of the vorticity stream function relation, several stationary sequences
are computed. The models obtained contain one or several large scale
circulations in the meridional plane. The configuration change due to
circulation is small, i.e., the shape is mainly determined by three
forces, the pressure gradient, the gravity, and the centrifugal force.
---------------------------------------------------------
Title: Carbon Combustion Supernovae: Numerical Studies of the Final
Evolution of Degenerate Carbon-Oxygen Cores
Authors: Mueller, E.; Arnett, W. D.
1986ApJ...307..619M Altcode:
The authors have performed and analyzed a set of numerical experiments
of the core carbon flash, which treat axisymmetric hydrodynamic flow
directly rather than use a phenomenological theory of convection. The
numerical experiments show a variety of possible evolutionary paths
for degenerate carbon-oxygen cores, ranging from spherical detonations
to nonspherical deflagrations. The results show that the initially
spherically symmetric burning front is Rayleigh-Taylor unstable. In
all experiments except the one leading to a detonation, some carbon
is not burned to nickel. Furthermore, all experiments lead to a total
disruption of the core, leaving no condensed remnant.
---------------------------------------------------------
Title: Nuclear-reaction networks and stellar evolution codes -
The coupling of composition changes and energy release in explosive
nuclear burning
Authors: Mueller, E.
1986A&A...162..103M Altcode:
A robust method is presented for calculating abundance changes and
entropy (or energy) generation with a nuclear-reaction network
within a stellar evolution code in case of explosive nuclear
burning. The robustness of the method is due to the fact that the rate
equations and the entropy (or energy) equation are solved together
by the Newton-Raphson technique. This guarantees that the strong
temperature dependence of the nuclear-reaction rates does not lead to
instabilities. The main advantage of the method is its capability to
calculate nuclear transmutations while entering or leaving the regime
of nuclear statistical equilibrium. This capability of the method
is demonstrated for an extreme test case. In addition an efficient
implementation of the method on vector processors is discussed.
---------------------------------------------------------
Title: Nuclear-reaction networks and stellar evolution codes: on
the coupling of composition changes and energy release in explosive
nuclear burning.
Authors: Müller, E.
1986ana..work..259M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Nuclear-reaction networks and stellar evolution codes: on
the coupling of composition changes and energy release in explosive
nuclear burning.
Authors: Müller, E.
1986MPARp.220.....M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Differentially Rotating Equilibrium Models - Collapse of
Rotating Degenerate Configurations
Authors: Muller, E.; Eriguchi, Y.
1986ASIC..163..143M Altcode: 1986ninp.proc..143M
No abstract at ADS
---------------------------------------------------------
Title: Equilibrium models of differentially rotating, completely
catalyzed, zero-temperature configurations with central densities
intermediate to white dwarf and neutron star densities
Authors: Mueller, E.; Eriguchi, Y.
1985A&A...152..325M Altcode:
We have calculated axisymmetric equilibria of differentially rotating,
completely catalyzed, zero-temperature Newtonian configurations with
central densities in the range 10 <SUP>7</SUP> gcm<SUP>-3</SUP> <=
Q<SUB>c</SUB> < 5 10<SUP>14</SUP> gcm <SUP>-3</SUP>. Our aim was
to address the following question: is it possible for rotating white
dwarfs with a mass larger than the Chandrasekhar mass to evolve, via
angular momentum losses, to a neutron star on a secular time scale,
i.e. without a sudden release of gravitational energy in the form
of an optical supernova outburst? Our results show that dynamically
stable (against collapse) rotating equilibrium models exist up to
densities of ≍ 10<SUP>11</SUP> gcm<SUP>-3</SUP> (without rotation
≍ 10 <SUP>9</SUP> gcm<SUP>-3</SUP>) and with masses up to 1.7
M<SUB>sun</SUB> (without rotation 1.0 M<SUB>sun</SUB>). Configurations
with masses in the range 1.7 < M/M<SUB>sun</SUB> < 2.2 are also
dynamically stable, but secularly unstable against non-axisymmetric
perturbations. We find that for all studied combinations of mass,
angular momentum and angular momentum distribution the evolution of a
rotating (cold) white dwarf must become dynamic at densities around
10<SUP>12</SUP> gcm<SUP>-3</SUP>, i.e. roughly 80 % of the neutron
star's binding energy will be released on a dynamical time scale.
---------------------------------------------------------
Title: Supernova-induced collapse of magnetic interstellar clouds
Authors: Oettl, R.; Hillebrandt, W.; Mueller, E.
1985A&A...151...33O Altcode:
The collapse of a cool and dense interstellar cloud induced by a
nearby supernova is studied. In the present model computations, the
cloud is assumed to be initially spherically symmetric and in pressure
equilibrium with the hot interstellar medium. In addition, the presence
of a homogeneous magnetic field parallel to the direction from the
supernova to the center of the cloud is assumed. The problem can then
be treated by means of a two-dimensional magnetohydrodynamic code. The
parameters which determine the model have been chosen in such a way
that: (1) the cloud would be Jeans-stable without the supernova shock;
(2) it would be compressed and collapse due to its self-gravity under
the influence of a strong shock, if magnetic fields were absent. It
is then found that a field of about 10 micro-G is required in order
to prevent a cloud of 5000 solar masses and an average density
of 8.3 x 10 to the -23rd g/cu cm from collapsing. These quantities
correspond to a ratio of magnetic to gravitational energy of about 3,
and a flux-to-mass ratio of roughly 12. For weaker fields, the cloud
becomes gravitationally unstable and collapses.
---------------------------------------------------------
Title: Equilibrium models of differentially rotating polytropes and
the collapse of rotating stellar cores
Authors: Eriguchi, Y.; Mueller, E.
1985A&A...147..161E Altcode:
Equilibrium models of axisymmetric, differentially rotating polytropes
are used to estimate the properties of rotating stellar cores at the
end point of their collapse. Results are presented for polytropes
with adiabatic indices of 4.3, 1.32, 1.29, and 1.25. The results are
in qualitative agreement with the results of earlier investigations,
which did not allow for changes in the shape of the configuration,
for the presence of density gradients, and for large differential
rotation. The analysis shows that a rotating stellar core will not
collapse all the way to neutron star densities on a dynamical time
scale, if its initial ratio of rotational to gravitational energy is
larger than some minimum value. The collapse stops due to rotation at
an intermediate, dynamically stable, axisymmetric equilibrium state,
and further evolution proceeds on a secular time scale.
---------------------------------------------------------
Title: A general computational method for obtaining equilibria of
self-gravitating and rotating gases
Authors: Eriguchi, Y.; Mueller, E.
1985A&A...146..260E Altcode:
A general computational method is presented to compute equilibria of
rapidly rotating self-gravitating gases. The superior capabilities of
this method as compared to previously published methods stem from the
fact that the equation of hydrostatic equilibrium and Poisson's equation
are solved simultaneously with a Newton-Raphson iteration scheme. To
demonstrate the capabilities of the method the authors have computed
equilibrium sequences of differentially rotating polytropes for several
rotation laws, and one equilibrium sequence using the ideal Fermi gas
equation of state. Although in these examples the pressure is a function
of the density only, a simple extension of the method allows to model
closely more realistic temperature-dependent equations of state.
---------------------------------------------------------
Title: Equilibrium models of differentially rotating, completely
catalyzed, zero-temperature configurations with central densities
intermediate towhite dwarf and neutron star densities.
Authors: Müller, E.; Eriguchi, Y.
1985MPARp.179.....M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Personal reminiscences of Adriaan Blaauw (I)
Authors: Müller, Edith A.
1985bems.symp..311M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Density functional calculations of the ground state properties
of atoms in strong magnetic fields.
Authors: Kössl, D.; Wolff, R. G.; Müller, E.; Hillebrandt, W.
1985MPARp.205.....K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Far-infrared-solar imaging from a balloon-borne platform
Authors: Degiacomi, K.; Kneubuehl, F. K.; Huguenin, D.; Mueller, E. A.
1984IJIMW...5..643D Altcode:
Far-infrared solar imaging with a balloonborne 60 cm-diameter Cassegrain
telescope is described and related to previous solar observations
in the millimeter range, the ir, vis and uv spectral regions. Solar
images have been taken at 50 μm, 80 μm and 200 μm and represented as
brightness temperature maps. The spectral windows observed correspond
to the transition zone chromosphere-phocosphere of the solar atmosphere
with a characteristic temperature minimum. Temperature enhancements
of a few 100 K over the temperature of the quiet sun are reported for
active solar regions, e.g. plages and sunspot regions. Far-infrared
images provide less spatial resolution but more reliable temperature
assignements than corresponding white-light, Ca II K and H<SUB>α</SUB>
pictures.
---------------------------------------------------------
Title: Equilibrium models of differentially rotating polytropes and
the collapse of rotating stellar cores.
Authors: Eriguchi, Y.; Müller, E.
1984MPARp.168.....E Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Neutrinos from collapsing stars.
Authors: Hillebrandt, W.; Müller, E.
1984npa..conf..229H Altcode:
Weak interaction processes leading to the production and emission of
neutrinos from collapsing stars are reviewed. Based on recent numerical
simulations of type II supernova explosions average electron neutrino
energies and luminosities are computed. It is shown that typically
a fast burst of neutrinos of energy 10 to 20 MeV and a luminosity of
around 10<SUP>54</SUP>erg s<SUP>-1</SUP> with a typical duration of
a few ms is expected when the supernova shock reaches the neutrino
sphere. Most of the neutrinos, however, are leaving the star on a
much longer timescale with significantly lower average energies and
luminosities.
---------------------------------------------------------
Title: Core Collapse Models of Type II Supernova Explosions
Authors: Hillebrandt, W.; Müller, E.
1984ASIC..134..183H Altcode: 1984pcnr.conf..183H
Core-collapse models of Type II supernova explosions are discussed. It
is shown that stellar models with about 9 M_sun; on the main sequence
do indeed lead to very energetic explosions, whereas more massive
stars (M ≅ 20 M_sun;) so far do not explode. It is found, however,
that the latter models are very close to mass ejection, and therefore
future improvements of stellar models, input physics and numerical
treatment may change these rather disappointing conclusions.
---------------------------------------------------------
Title: The Collapse of Rotating Stellar Cores: the Amount of
Gravitational Radiation Predicted by Various Numerical Models
Authors: Müller, E.
1984ASIC..134..271M Altcode: 1984pcnr.conf..271M
The amount of gravitational radiation predicted by numerical
calculations of the collapse of rotating stellar cores is
reviewed. Currently the most realistic models suggest an energy loss of
the order 10<SUP>-6</SUP>M_sun;c<SUP>2</SUP>. For a source situated at a
distance of 10 Mpc (≈Virgo Cluster) the corresponding (dimensionless)
wave amplitude h is smaller than 10<SUP>-22</SUP>, which seems to
be even beyond the realm of the third generation gravitational wave
detectors. On the other hand non-axisymmetric models predict up to
100 times larger radiative efficiencies. The uncertainties in these
calculations are examined.
---------------------------------------------------------
Title: Variational calculation of iron and helium atoms and molecular
chains in superstrong magnetic fields
Authors: Mueller, E.
1984A&A...130..415M Altcode:
The ground-state energy of iron atoms and molecular chains
in superstrong magnetic fields (1-5 10 to the 12th Gauss)
is recalculated. A 10 percent higher binding energy of the atoms
and only a 1 percent higher binding energy of the molecular chains
are found as compared to a previous investigation (Flowers et al.,
1977). Therefore the calculations suggest that atoms are energetically
more favorable than molecular chains in contradiction to the earlier
results of Flowers et al. (1977). In addition, similar calculations
for helium atoms and molecular chains have been performed. In this
case it is found that, for B = 1 x 10 to the 12th Gauss the chains
are bound with 50 eV relative to the free atoms. For B = 5 x 10 to
the 12th Gauss the cohesive energy amounts to 190 eV.
---------------------------------------------------------
Title: Neutrinos from collapsing stars
Authors: Müller, E.
1984npa..conf..229M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Astronomy Education at Universities
Authors: Muller, E. A.
1984aprm.conf..227M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Carbon Combustion Supernovae
Authors: Muller, E.
1983nuas.proc...40M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Carbon combustion supernovae.
Authors: Müller, E.
1983MPARp..90...40M Altcode:
The author has performed a set of axisymmetric hydrodynamic numerical
experiments of the core carbon flash, which incorporate the treatment
of two-dimensional convection without the need of a phenomenological
theory of convection. The numerical experiments show a variety of
possible evolutions of degenerate carbon-oxygen cores ranging from
spherical detonations to non-spherical deflagrations.
---------------------------------------------------------
Title: Gravitational Radiation from Collapsing Rotating Stellar Cores
Authors: Muller, E.
1982ASIC...90..157M Altcode: 1982sscr.conf..157M
No abstract at ADS
---------------------------------------------------------
Title: Numerical studies of nonspherical carbon combustion models
Authors: Mueller, E.; Arnett, W. D.
1982ApJ...261L.109M Altcode:
First results of axisymmetric numerical studies of the final evolution
of degenerate C + O cores are reported. The two-dimensional convective
flow is treated without a phenomenological theory of convection. The
computations show that, in the beginning, the nuclear burning propagates
slowly outward from the center of the star in a spherical combustion
front. Small-scale eddies form, giving rise to bumps in the front. The
bumps grow into blobs and eventually into fingers, which steadily
elongate relative to the rest of the combustion front. This behavior
is not well described by either the detonation or deflagration models,
being more complex than either.
---------------------------------------------------------
Title: Gravitational radiation from collapsing rotating stellar cores
Authors: Mueller, E.
1982A&A...114...53M Altcode:
A post-Newtonian multipole formalism is invoked in a discussion of the
gravitational radiation produced by the axisymmetric, Newtonian collapse
models of rotating stellar cores examined by Mueller and Hillebrandt
(1981). The results of calculations of waveforms and energy losses of
the two lowest order multipoles, together with the energy spectrum of
the quadrupole radiation, indicate that the gravitational wave signals
from supernovae are weaker than earlier, less sophisticated collapse
calculations suggested. Total energy loss in the form of gravitational
waves is less than 0.000001 of the product of solar mass and c-squared,
even for rapidly rotating stellar cores, and for a source located at
a distance of 10 Mpc, the corresponding dimensionless wave amplitude
is smaller than 10 to the -22nd.
---------------------------------------------------------
Title: Computer simulations of stellar collapse and shock wave
propagation
Authors: Hillebrandt, W.; Mueller, E.
1981A&A...103..147H Altcode:
Using recent progress in deriving realistic equations of state of
matter at high densities and temperatures, the gravitational collapse
of cores of massive stars through core-bounce at neutron star densities
is calculated. In particular, the sensitivity of the results is analyzed
with respect to details of the equation of state, neutrino emissivities
in the shock region, and properties of the hydrocode. In none of the
cases considered is the core-bounce followed by an explosion of the
stellar mantle. Although a shock forms in every case, it is never strong
enough to accelerate matter beyond the escape velocity. The result is
found to be independent of both the details of the equation of state
and the assumptions about neutrino losses from the shocked matter.
---------------------------------------------------------
Title: The collapse of rotating stellar cores
Authors: Mueller, E.; Hillebrandt, W.
1981A&A...103..358M Altcode:
The collapse of the rotating cores of massive stars (M greater than
or equal to 15 solar masses) is considered. The dynamical evolution
of the core is followed by an explicit two-dimensional hydrodynamic
code. A realistic, finite-temperature equation of state is used
in the calculations. Rigidly and differentially rotating initial
models are both studied. It is found that in all cases considered the
collapse proceeds up to nearly nuclear matter density before it is
stopped. In none of the examined models is the core-bounce followed by
an explosion. The dynamical behaviour of the slowly rotating models is
very similar to that of nonrotating models. The rapidly rotating cores
already show large nonspherical effects before core bounce. In these
models, a high entropy blob is formed near the axis of rotation, which,
while trying to rise and expand, is rapidly destroyed by the onset
of circulation. A flattened, nearly hydrostatic central condensation
builds up with relatively low central density on which the matter of
the envelope is further accreted.
---------------------------------------------------------
Title: Numerical Studies of the Non-spherical Core Carbon Flash
Authors: Müller, E.; Arnett, W. D.
1981BAAS...13..791M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Far-IR observations of active regions at sunspots with a
balloon-borne 60 cm telescope.
Authors: Cartier, F.; Kneubühl, F.; Huguenin, D.; Müller, E. A.
1981imw..conf..W31C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A comparison between the observed and predicted UV line
blocking for blanketed model atmospheres of early type stars
Authors: Castelli, F.; Lamers, H. J. G. L. M.; de Andres, F. L.;
Mueller, E. A.
1980A&A....91...32C Altcode:
For early B main-sequence and giant stars the observed near-UV blocking
factors are larger than those predicted by blanketed model atmospheres
with a microturbulence of 2 km/sec. Better agreement would be reached
if a microturbulence of 4 to 5 km/sec were adopted. Evidence was found
that the line opacities due to doubly ionized metals are unsufficiently
accounted for in the model atmospheres. For late B main-sequence and
giant stars the observed near-UV blocking is smaller than predicted
which points to an over-estimation of the line opacities due to singly
ionized metals. The observed blocking in early B supergiants is much
larger than predicted and would require a microturbulence of 10 km/sec
at least. If this large blocking extends to the far UV, the energy
distribution given by the models might be changed drastically.
---------------------------------------------------------
Title: Book-Review - IAU Transactions V.17A - Reports on Astronomy
Authors: Muller, E. A.; Tayler, R. J.
1980Obs...100..131M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Variability of the far-infrared solar temperature minimum
with the solar cycle
Authors: Mueller, E. A.; Kneubuehl, F. K.; Rast, J.; Stettler, P.
1980A&A....87L...3M Altcode:
Measurements of the absolute solar brightness temperature in
the far-infrared, carried out since 1971 with a balloon-borne
lamellar-grating interferometer, have revealed (1) a flat minimum of the
temperature profile in the spectral range between 60 and 100 kaysers,
and (2) a variation of the temperature minimum with time. It is shown
here that the variation of the solar temperature minimum observed
from 1971 to 1978 is systematic and congruent with the variation of
the yearly mean of the Zuerich Relative Sunspot Numbers over the same
period of time. This suggests that the value of the solar temperature
minimum varies with the solar cycle.
---------------------------------------------------------
Title: Measurement of the absolute solar brightness temperature in
the far-infrared with a balloon-borne interferometer
Authors: Rast, J.; Cartier, F.; Kneubuehl, F. K.; Huguenin, D.;
Muller, E. A.
1980A&A....83..199R Altcode:
The absolute solar brightness temperature was measured with a
stratospheric balloon-borne lamellar-grating interferometer in the
spectral region 15 cm<SUP>-1</SUP> to 100 cm<SUP>-1</SUP> on the
occasion of two flights. The results are compared with previous
measurements and the models of the solar atmosphere by Vernazza et
al. (1976).
---------------------------------------------------------
Title: Stellar collapse - Adiabatic hydrodynamics and shock wave
propagation
Authors: Mueller, E.; Hillebrandt, W.; Rozyczka, M.
1980A&A....81..288M Altcode:
The consistency of the shock wave description in an adiabatic
approximation of supernova explosions (Van Riper, 1978) is examined. It
is shown that shock propagation cannot be simulated correctly and
that whether or not mass is ejected from the rebounding core strongly
depends on the treatment of energy dissipation in the shock. It
appears therefore that the question of whether purely hydrodynamic
effects can cause supernova explosions cannot be answered with
the help of adiabatic models. This conclusion remains valid for
two-dimensional (i.e. axisymmetric) simulations of the collapse of
rotating configurations. On the other hand, the experiments in two
dimensions show some new interesting effects which do not depend on
the treatment of the shock front.
---------------------------------------------------------
Title: Book-Review - Reports on Astronomy
Authors: Muller, E. A.
1980S&T....59T.154M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Measurement of the spectrum of the sun in the far infrared.
Authors: Rast, J.; Cartier, F.; Kneubühl, F.; Huguenin, D.; Mueller,
E. A.
1980AcHPh..52..400R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Introduction, by the CHAIRMAN
Authors: Müller, Edith A.
1980fsoo.conf..181M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On Asymmetries of Solar Spectral Lines
Authors: Barambon, C.; Mueller, E. A.
1979SoPh...64..201B Altcode:
The profiles of 43 lines have been observed at the centre and near the
limb of the solar disk. Their asymmetry decreases towards the limb,
and increases with the equivalent width and the mean heigth of line
formation; no relation was found between the asymmetry and the line
excitation potential, nor with the degree of ionization, nor with the
usually adopted macroturbulent velocity. The asymmetry appears to be
due to radial movements.
---------------------------------------------------------
Title: A magnetohydrodynamical supernova model.
Authors: Mueller, E.; Hillebrandt, W.
1979A&A....80..147M Altcode:
A model for supernova explosions of massive stars in which mass ejection
is caused by a two-step process is presented. In the first stage the
rebounce of the core at nuclear density generates a hydrodynamical shock
wave; if this shock is not sufficient for mass ejection reimplosion
of the stellar mantle results. During collapse the core spins much
more rapidly than the mantle amplifying the magnetic field by winding
the magnetic field lines. For sufficiently large initial magnetic
field strength values the magnetic pressure becomes comparable to the
thermal pressure in a small region near the collapsed core, pushing
the matter outwards, and thus generating a second magnetohydrodynamical
shock. Results showed mass ejection with energies of about several times
10 to the 50th power erg leaving behind a neutron star of approximately
1-1.5 solar mass.
---------------------------------------------------------
Title: Line blocking in the near ultraviolet spectrum of early
type stars. II. The dependence on spectral type and luminosity for
normal stars.
Authors: Llorente de Andres, F.; Lamers, H. J. G. L. M.; Muller, E. A.
1979A&AS...38..367L Altcode:
The variation with luminosity and spectral type of the line blocking
in the near-UV spectrum of "normal" O8 to A2 stars is studied. In the
2500 A and the 2800 A region the blocking increases from O8 to A2 due
to lines of singly ionized metals. In the 2100 A region the blocking
reaches a maximum at B0.5 for main-sequence stars, at B2 for giants
and at B3 for supergiants, which is due to lines of twice ionized
metals. The blocking in supergiants is about twice as large as in
main-sequence stars; this can be explained by the larger microturbulent
velocity of about 10 km/s in supergiants. A few "normal" stars were
found to have an anomalous UV-blocking. Key words: Ultraviolet spectrum
Early type stars - Line blocking
---------------------------------------------------------
Title: A magnetohydrodynamic supernova model
Authors: Mueller, E.
1979PhDT.........2M Altcode:
A quasi-spherical model is developed for the supernova explosion of
a massive rotating magnetic star. The dynamic development that leads
to the explosion is represented in three phases: the collapse phase,
the field intensification phase, and the explosion phase. Numerical
results show that the explosion leads to the ejection of masses with
energies of 10 to the 50th erg, leaving behind a rotating magnetic
neutron star with a mass of 0.8-1.5 solar masses. A physical description
and mathematical formulation of the model are given and calculations
are presented with and without consideration of the magnetic field.
---------------------------------------------------------
Title: Minimum far infrared solar brightness temperature and sunspot
activity.
Authors: Kneubühl, F. K.; Rast, J.; Stettler, P.; Muller, E. A.;
Huguenin, D.
1979imwa.conf..177K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Reports on Astronomy.
Authors: Müller, E. A.
1979IAUTA..17.....M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: International Astronomical Union, Information Bulletin. No. 41.
Authors: Müller, E. A.
1979IAUIB..41.....M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Measurement of the solar brightness temperature near its
minimum with a balloon-borne lamellar-grating interferometer.
Authors: Rast, J.; Kneubuhl, F. K.; Muller, E. A.
1978A&A....68..229R Altcode:
For the measurement of the absolute solar brightness temperature in the
far-infrared, an improved balloon-borne lamellar-grating interferometer
and a blackbody calibration source were built. During the first two
flights in 1975/76 a flat temperature profile was observed between
60 and 110 kaysers, with a minimum of 4530 K plus 100 K/-150 K. The
accuracy of this measurement permits a decision to be made in favor of
the present models of the solar atmosphere. From the measured residual
terrestrial absorption above 33.5 km an average water-vapor volume
mixing ratio of 6.3 plus or minus 1.6 ppm is determined.
---------------------------------------------------------
Title: Line blocking in the near ultraviolet spectrum of early type
stars. I. Observed blocking factors for 132 stars.
Authors: Lamers, H. J. G. L. M.; Mueller, E. A.; Llorente de Andres, F.
1978A&AS...32....1L Altcode:
The line blocking factors in the ultraviolet spectrum of 132 stars
of types O4 to A7 observed by the S59 experiment are presented. The
blocking factors are given for intervals of 10 A wide in the wavelength
ranges of 2070-2150 A, 2505-2585 A and 278() 2860 A as well as for
these whole intervals. The accuracy of the blocking factors is given in
terms of a 2o error. The intrinsic continuum colors - , - , and rn2500-
V0 are also given.
---------------------------------------------------------
Title: Transport of angular momentum by magnetic fields during the
gravitational collapse of rotating massive stars
Authors: Hillebrandt, W.; Mueller, E.
1978MitAG..43..236H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Transport of Angular Momentum by Magnetic Fields During the
Gravitational Collapse of Rotating Massive Stars
Authors: Hillebrandt, W.; Müller, E.
1978MitAG..43Q.236H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: International Astronomical Union, Information Bulletin. No. 40.
Authors: Müller, E. A.
1978IAUIB..40.....M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: International Astronomical Union, Information Bulletin. No. 39.
Authors: Müller, E. A.
1978IAUIB..39.....M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Variational calculation of ground-state energy of iron atoms
and condensed matter in strong magnetic fields.
Authors: Flowers, E. G.; Ruderman, M. A.; Lee, J. -F.; Sutherland,
P. G.; Hillebrandt, W.; Mueller, E.
1977ApJ...215..291F Altcode:
Variational calculations of the binding energies of iron atoms and
condensed matter in strong magnetic fields (greater than 10 to the 12th
gauss). These calculations include the electron exchange energy. The
cohesive energy of the condensed matter, which is the difference
between these two binding energies, is of interest in pulsar theories
and in the description of the surfaces of neutron stars. It is found
that the cohesive energy ranges from 2.6 keV to 8.0 keV.
---------------------------------------------------------
Title: Space missions to the moon and planets. Joint discussion at
the XVIth General Assembly of the I.A.U., Grenoble, 1976.
Authors: Müller, E. A.
1977smmp.conf.....M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Highlights of Astronomy, Vol._4, Parts I and II. as presented
at the XVIth General Assembly of the I.A.U., Grenoble, 1976.
Authors: Müller, E. A.
1977havp.book.....M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Transactions of the International Astronomical Union, Volume
XVI B: Proceedings of the Sixteenth General Assembly, Grenoble 1976.
Authors: Müller, E. A.; Jappel, A.
1977tiau.book.....M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Highlights of astronomy. Volume 4 - International Astronomical
Union, General Assembly, 16th, Grenoble, France, August 24-September
2, 1976, Proceedings. Parts 1 & 2
Authors: Mueller, E. A.
1977HiA.....4.....M Altcode:
The papers deal with space missions to the moon and planets, X-ray
binaries and compact objects, clusters of galaxies, space astrometry,
Galactic structure toward the poles, the small-scale structure of solar
magnetic fields, the impact of UV observations on stellar spectral
classification, and observational evidence for heterogeneities
on stellar surfaces. Specific topics include IR observations of
interstellar dust, a review of in situ planetary observations by
spacecraft, transient X-ray sources, X-ray bursts, the evolutionary
history of X-ray binaries, accretion flows in binary X-ray systems, the
magnetic field of Mercury, and lunar magnetism. Other papers examine
cratering of terrestrial planets, the dynamical evolution of clusters
of galaxies, X-rays from clusters of galaxies, hot gas in clusters,
the microwave background radiation toward various clusters, the Large
Space Telescope astrometric instrument, and the space density of M
dwarfs. The Galactic mass density in the vicinity of the sun is also
discussed as well as the distribution of field horizontal-branch stars
in the Galactic halo, polarization measurements and extinction near the
North Galactic Pole, the decay of light elements in stellar envelopes,
observations of solar small-scale photospheric magnetic fields, EUV
observations of white dwarfs, and an atlas of UV stellar spectra.
---------------------------------------------------------
Title: The Solar Brightness Temperature in the Far Infrared (Abstract)
Authors: Müller, E. A.; Stettler, P.; Rast, J.; Kneubühl, F. K.;
Huguenin, D.
1977ASSL...63..107M Altcode: 1977isa..symp..107M
No abstract at ADS
---------------------------------------------------------
Title: De Internationale Astronomische Unie.
Authors: Müller, E. A.
1977Zenit...4...42M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: International Astronomical Union, Information Bulletin. No._37.
Authors: Müller, E. A.
1977IAUIB..37.....M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: International Astronomical Union, Information Bulletin. No._38.
Authors: Müller, E. A.
1977IAUIB..38.....M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: International Astronomical Union, General Assembly, 16th,
Grenoble, France, August 24-September 2, 1976, Proceedings
Authors: Mueller, E. A.; Jappel, A.
1977IAUTB..16.....M Altcode: 1977IAUT...16.....M
Resolutions adopted by the General Assembly of the International
Astronomical Union are considered, taking into account astronomical
constants, astronomy and astrophysics abstracts, atomic and
molecular data, the international solar system program, polar
motion, the protection of the radio spectrum and observatory sites,
and the resolutions adopted by the commissions. Reports of meetings
of commissions are also presented, giving attention to ephemerides,
documentation, astronomical telegrams, celestial mechanics, positional
astronomy, instruments and techniques, solar activity, radiation and
structure of the solar atmosphere, comets and meteorites, planets and
satellites, the moon, the rotation of the earth, the light of the night
sky, photographic astrometry, stellar photometry and polarimetry, double
stars, variable stars, galaxies, stellar spectra, radial velocities,
time, interstellar matter and planetary nebulae, stellar constitution,
star clusters, and cosmology.
---------------------------------------------------------
Title: Matter in superstrong magnetic fields and the structure of
a neutron star's surface.
Authors: Hillebrandt, W.; Mueller, E.
1976ApJ...207..589H Altcode:
The properties of matter in strong and superstrong magnetic fields (B 5
x gauss) are reconsidered. By slightly improving and correcting previous
calculations it is shown that molecular chains are only slightly bound
with respect to free atoms. For B = 1012 gauss the cohesive energy
is 0.11 keV and 0.29 keV for iron and carbon, respectively. Only at
extremely high magnetic fields (B > 5 x 10' gauss), which are
probably not present in pulsars, do we get strong binding (>10
keV). Subject headings: dense matter - magnetic fields - stars: neutron
---------------------------------------------------------
Title: The solar brightness temperature in the far infrared
Authors: Mueller, E. A.; Huguenin, D.; Stettler, P.; Rast, J.;
Kneubuehl, F. K.
1976cosp.meetR....M Altcode:
Measurements of absolute solar brightness have been obtained for
a wide range of far-infrared and submillimeter wavelengths using a
balloon-borne lamellar grating interferometer. An experiment covering
the wavelength range 200-600 microns showed that at 200 microns the
solar brightness temperature may reach a value of about 4100 K, a result
not incompatible with the higher values of the temperature minimum
derived from ultraviolet observations around 1600 A. The brightness
temperature is constant between about 95 and 200 microns, corresponding
to the flat temperature minimum of the photosphere/chromosphere
transition region. Some of the spectra obtained have a spectral
resolution better than 0.5/cm, allowing the detection of a number of
stratospheric molecular absorption lines (H2O, O2, O3).
---------------------------------------------------------
Title: Properties of matter in strong and superstrong magnetic fields.
Authors: Müller, E.; Hillebrandt, W.
1976MitAG..38..120M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Measurement of the solar brightness temperature between 85
and 250 µ with a balloonborne lamellar grating interferometer.
Authors: Rast, J.; Kneubühl, F.; Müller, E. A.
1976AcHPh..49..754R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The solar beryllium abundance.
Authors: Chmielewski, Y.; Brault, J. W.; Mueller, E. A.
1975A&A....42...37C Altcode:
An interpretation of high-resolution centerlimb observations of the Be
II resonance lines in the solar spectrum is given. It is shown that to
account for the observed spectrum, it is necessary to allow for (1)
a source of additional opacity in the UV continuum which was derived
empirically for the HSRA (Harvard Smithsonian Reference Atmosphere)
and revised Holweger (1974) models and (2) departures from LTE in the Be
I-Be II system. It is found that the 2p(3)P(0) metastable level of Be I
is significantly underpopulated and that beryllium is more ionized than
expected in the case of local thermodynamic equilibrium. The kinetic
equilibrium calculations yield a logarithmic beryllium abundance of
approximately 1.15 (on the basis of a logarithmic hydrogen abundance
of 12.00), which is in agreement with previous determinations based
on the LTE assumption.
---------------------------------------------------------
Title: Matter in superstrong magnetic fields and the structure of
a neutron star's surface
Authors: Hillebrandt, W.; Mueller, E.
1975STIN...7625119H Altcode:
The properties of matter in strong and superstrong magnetic fields (B in
the range of 5 x 10 to the 11th power to 10 to the 13th power Gauss) are
reconsidered. By slightly improving and correcting previous calculations
it is shown that molecular chains are only slightly bound with respect
to free atoms. For B = 10 to the 12th power Gauss the cohesive energy
is 0.07 keV and 0.19 keV for iron and carbon respectively. Only at
extremely high magnetic fields (B greater than or equal to 5 x 10
to the 14th power Gauss), which are probably not present in pulsars,
strong binding is obtained (greater than 10 keV).
---------------------------------------------------------
Title: The Potassium Abundance in the Solar Photosphere
Authors: de La Reza, R.; Mueller, E. A.
1975SoPh...43...15D Altcode:
High precision center-limb spectrograms of the K I resonance doublet
line at λ 7699 Å were used to study the line formation and to
determine the abundance of potassium in the solar atmosphere. The LTE
assumption is not valid for these lines. Synthetic profiles computed
in NLTE reproduce very well the observed center-limb line behaviour
and yield logɛ<SUB>K</SUB> = 5.14±0.10 for the solar abundance of
potassium (on the scale of logɛ<SUB>H</SUB> = 12 for Hydrogen).
---------------------------------------------------------
Title: The Solar Lithium Abundance. I: Observations of the Solar
Lithium Feature at λ 6707.8 Å
Authors: Brault, J. W.; Mueller, E. A.
1975SoPh...41...43B Altcode:
A detailed observational study of the solar photospheric lithium
feature has been carried out with emphasis on center-limb observations,
continuum location, possible effects of telluric lines, effects of
blending by atomic and molecular lines, and decomposition of the solar
spectrum around λ6707 Å.
---------------------------------------------------------
Title: The Solar Lithium Abundance. II: Synthetic Analysis of the
Solar Lithium Feature at λ 6707.8 Å
Authors: Müller, Edith A.; Peytremann, Eric; de la Reza, Ramiro
1975SoPh...41...53M Altcode:
The solar abundance of lithium and its isotopic abundance ratio
were determined by comparing synthetic spectra with the high quality
center-to-limb spectra of the solar lithium feature presented in Paper
I by Brault and Müller (1974). The following possible effects on the
abundance result were considered: deviations from LTE, atmospheric
models, blends by molecular and atomic lines, hyperfine structure,
large scale velocity fields. It was found that the photospheric
lithium abundance is logɛ<SUB>Li</SUB>=1.0±0.1. The greatest
uncertainty is due to differences in the atmospheric models. The
NLTE abundance result is 0.05 dex smaller than the LTE value. A
mean depth of line formation was determined for the Li<SUP>7</SUP>I
λ16707.776 Å line. The lithium isotopic abundance ratio was found
to be Li<SUP>6</SUP>/Li<SUP>7</SUP>⩽0.01.
---------------------------------------------------------
Title: Far-Infrared Solar Brightness Measured with a Balloon-Borne
Lamellar-Grating Interferometer
Authors: Stettler, P.; Rast, J.; Kneubuehl, F. K.; Mueller, E. A.
1975SoPh...40..337S Altcode:
The solar brightness temperature was measured at wavelengths between
208μ and 660μ with a lamellar-grating interferometer. In order to
avoid terrestrial absorption due to water vapor the measurement of the
absolute spectral brightness was performed at altitudes of 30 km and
35 km with a balloon borne gondola. A cylindrical black body radiation
source served as absolute calibration standard. Its wall temperature
lay between 1100 K and 1300 K. Since the box of the interferometer and
the black body could not be evacuated for the calibration, the air
in the system was replaced by dry nitrogen. Nevertheless, residual
water vapor absorption lines hampered the precision of the absolute
calibration. The corresponding error could not be reduced to less than
±100 K. The present experimental temperature profile is compared to
results obtained from other measurements. The results agree with the
empirical HSRA model and with those of other research groups in the
spectral range between 208μ and 660μ.
---------------------------------------------------------
Title: Book reviews
Authors: van de Stadt, Herman; Rawer, Karl; Schadee, A.; Noyes, R. W.;
Bleeker, J. A. M.; Wittenberg, H.; de Graaff, W.; Akasofu, S. -I.;
Hooykaas, R.; Bappu, M. K. V.; Atanasijević, I.; Icke, Vincent;
van der Valk, F.; Kresàk, L.; Müller, Edith A.
1975SSRv...17..159V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The solar brightness temperature in the far infrared.
Authors: Müller, E. A.; Stettler, P.; Rast, J.; Kneubühl, F. K.;
Huguenin, D.
1975MmArc.105...90M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The solar brightness temperature in the far infrared
Authors: Müller, E. A.; Stettler, P.; Rast, J.; Kneubühl, F. K.;
Huguenin, D.
1975cesra...5...90M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Photospheric Barium Spectrum: Solar Abundance and Collision
Broadening of Ba II Lines by Hydrogen
Authors: Holweger, H.; Mueller, E. A.
1974SoPh...39...19H Altcode:
A study of the solar Ba II spectrum leads to a solar abundance of
barium of logεBa = = 2.11±0.12, on the scale logεH = 12. The observed
asymmetry of the resonance line λ4554 is consistent with an isotopic
abundance ratio equal to the terrestrial one. The meteoritic Ba/Si
abundance ratio found in carbonaceous chondrites appears to exceed
the solar ratio by 0.1 to 0.2 dex (Section 5).
---------------------------------------------------------
Title: Vacation courses in astronomy for graduates and teachers.
Authors: Müller, E. A.
1974Obs....94..110M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Submillimeter-wave solar brightness temperature measured with
a balloon-borne lamellar-grating interferometer.
Authors: Stettler, P.; Rast, J.; Kneubühl, F.; Müller, E. A.
1974swa..conf..163S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Teaching of astronomy (Enseignement de l'astronomie).
Authors: Müller, E. A.
1973IAUTA..15..717M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Absolute Measurement of the Solar Brightness in the Spectral
Region between 100 and 500 Microns
Authors: Stettler, P.; Kneubuh, F. K.; Muller, E. A.
1972A&A....20..309S Altcode:
Summary. The solar brightness temperature at wavelengths between 110 and
500 was measured with a balloon-borne lamellar-grating interferometer. A
high temperature black body served as absolute calibration source. The
experimental results are compared with those of other research groups
and with the empirical HSRA model. The agreement with the model is
fairly good for wavelengths greater than 300 t. Key words: sun -
far-infrared - interferometry - stratosphere
---------------------------------------------------------
Title: International conference on education in and history of modern
astronomy. held at the American Museum of Natural History on August
30 and 31 and September 1, 1971.
Authors: Berendzen, R.; Müller, E. A.
1972NYASA.198..275B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Commission on the Teaching of Astronomy of the
International Astronomical Union.
Authors: Mueller, E. A.
1972NYASA.198...66M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Teaching of Astronomy (Enseignernent de 1'Astronomie)
Authors: Müller, E. A.
1971IAUTB..14..236M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Teaching of astronomy.
Authors: Müller, E. A.
1970IAUTA..14..559M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Astronomy education material (Prepared by I.A.U. Commission
46 - Teaching of Astronomy).
Authors: Müller, E. A.
1970aem..book.....M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Book reviews
Authors: Nicolet, M.; Müller, Edith A.; de Jager, C.; Rutten, H. S.;
Millman, P. M.; Fielder, G.
1969SSRv...10..314N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Lithium Observations in the Sun
Authors: Müller, Edith A.
1968HiA.....1..243M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Center-to-Limb Analysis of the Solar Oxygen Lines
Authors: Müller, Edith A.; Baschek, Bodo; Holweger, Hartmut
1968SoPh....3..125M Altcode:
Several lines of neutral oxygen observed at various positions on the
solar disk were used to study the influence of (1) the temperature
distribution, (2) the velocity field, and (3) the damping on the line
profiles and the abundance of oxygen in the photosphere. Theoretical
profiles were calculated on the basis of four different model
atmospheres in LTE. It was found that the model proposed by HOLWEGER
(1967) best reproduced the center-to-limb observations of the lines
studied. The weighted mean of the oxygen abundance turned out to be
log ɛ<SUB>O</SUB> = 8.83 on the basis of log ɛ<SUB>H</SUB> = 12.00.
---------------------------------------------------------
Title: The Composition of the Solar Atmosphere
Authors: Müller, E. A.
1967sp...conf...33M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Critical Discussion of the Abundance Results in the Solar
Atmosphere
Authors: Müller, E. A.
1966IAUS...26..171M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Effects of Deviations from Local Thermodynamic Equilibrium
on Solar Abundances
Authors: Muller, Edith A.; Mutschlecner, J. Paul
1964ApJS....9....1M Altcode:
Investigations of center-to-limb variations of curves of growth
were carried out in order to detect effects of deviations from local
thermodynamic equilibrium on solar abundances. The neutral stages of
the elements Ca, Ti, V, Cr, Mn, Fe, and Co were considered. For three
positions on the solar disk, = 1.0, 0.5, and 0.3, theoretical curves
of growth were computed by the weighting-function method employing
a new semi-empirical solar model and new partition functions. The
observed curves of growth were constructed with the most reliable
f-values available and with equivalent widths measured on three solar
spectrum atlases of the McMath-Hulbert Observatory of the University
of Michigan traced at the three values of . No systematic variation of
the abundances from center to limb or from lower to higher excitation
lines could be detected. This indicates that the assumption of local
thermodynamic equilibrium does not introduce large errors in the solar
abundances of the elements in the iron group. The high quality of the
observational and theoretical data employed in this investigation should
make possible reliable results for the abundances of the elements in
the iron group. The choice of the absolute f-value scale is still very
questionable, however, and completely trustworthy abundances cannot
yet be obtained.
---------------------------------------------------------
Title: Center-Limb Effects on Solar Abundances.
Authors: Müller, Edith A.; Mutschlechner, J. Paul
1962AJ.....67T.277M Altcode:
Several investigators have pointed out that deviations from local
thermodynamic equilibrium (LTE) can introduce large differences between
the electron temperature and the excitation temperature. Accordingly,
for photospheric models that neglect deviations from LTE one might
expect large discrepancies in the abundance of an element when the
calculations are based on lines that are formed in different layers
of the photosphere, i.e.,lines observed at different points on the
solar disk and lines of different excitation potentials. The purpose
of this investigation has been to determine whether or not such
discrepancies exist for elements in the iron group, and if they do
exist, to determine their magnitude. The elements of the iron group
were chosen for investigation because (a) for these elements a number
of faint and medium-strong lines of different excitation potential are
observed in the solar spectrum, and (b) reliable experimental relative
f values are available. The lines were observed at the three positions
on the solar disk ~-- 1.0, 0.5, and 0.3 with the vacuum spectrograph at
the MeMath-Hulbert Observatory by Dr. Mohler and his associates. The
equivalent widths of blended lines were determined by the Utrecht
method. A homogeneous model of the photosphere, assuming LTE, was
employed in which the recently observed temperature distributions
are included. The theoretical calculations of the equivalent widths
by the weighting function method were carried out with the aid of the
IBM 704 computer of The University of Michigan. Individual curves of
growth were calculated for each element for various sets of wavelengths
and excitation potentials. The observed lines of each element were
separated into groups according to their excitation potentials. For
each element and for each position on the solar disk, the individual
groups of lines were plotted separately on a curve of growth diagram
and individual abundances derived. No systematie variation of the
abundances from center to limb or from lower to higher excitation
lines could be detected. This result indicates that the assumption of
LTE in the photospheric model does not introduce great discrepancies
in the solar abundances of the elements in the iron group. This work
was supported in part by Contract Nonr-1224(19), NR 015-320 with the
Office of Naval Research.
---------------------------------------------------------
Title: The Abundances of the Elements in the Solar Atmosphere.
Authors: Goldberg, Leo; Muller, Edith A.; Aller, Lawrence H.
1960ApJS....5....1G Altcode:
The method of weighting functions has been utilized to derive the
abundances of forty-two elements from faint and medium-strong lines
in the solar spectrum. The model atmosphere adopted is that of Aller
and Pierce as extended by Elste to both higher and deeper layers. The
chief sources of equivalent widths were the measurements by Allen and by
the Utrecht astronomers, but a substantial number of new measurements
were included from McMath-Hulbert Observatory data. TheJ-values were
taken from many different sources, but, whenever possible, experimental
measurements were employed. When laboratory data were not available,
they were replaced by theoretical values based on the assumption of LS
coupling and making use of the f-sum rule or of the Bates and Damgaard
tables for the absolute scale factor. A detailed description is given
of the derivation of the abundance of each element, including the major
sources of uncertainty, such as the errors in the measurement of weak
lines throughout the spectrum and of all lines in the ultraviolet
region, uncertainties in the solar model for ultraviolet lines, and
the unreliable character of many of the f-values employed.
---------------------------------------------------------
Title: The Double Reversal in the Cores of the Fraunhofer H and
K Lines.
Authors: Goldberg, Leo; Mohler, O. C.; Müller, Edith A.
1959ApJ...129..119G Altcode:
Observations are presented of the profiles of the central doubly
reversed cores of the H and K lines of Ca ii in the Fraunhofer
spectrum. The profiles were obtained photoelectrically with the
vacuum spectograph of the McMath-Hulbert Observatory at five different
points on the solar disk from M = 1.0 to = 0.2. At the center of the
disk the central intensities of H and K are 2.95 and 2.36 per cent,
respectively, in terms of the neighboring continuous spectrum near
X 4000. At = 0.2 the central intensities are 2.41 and 2.01 per cent
for H and K, respectively, also with reference to the continuum at
X 4000 at the center of the disk. The relative intensity ratio H:
K is found to be constant in the inner absorption core and nearly
the same for all values of . This suggests that the logarithm of
the source function varies linearly with the logarithm of Nh, the
number of Ca ii atoms per square centimeter above height, h, in the
chromosphere. The Doppler widths were derived by two methods, namely,
(1) by an intercomparison method which is independent of the source
functiop and (2) by using the depth-dependence of the source function
and the shapes of the profiles. The Doppler widths thus found increase
from 0.063 A at = 1.0 to 0.110 A at = 0.2. The derived Doppler widths
and source function are employed to calculate the profiles of the
inner cores of H and K. Extremely good agreement is found between the
calculated and the observed central cores at all five values of . The
variation in the Doppler widths from center to limb is discussed,
and it is concluded that the widening of the profiles to the limb
is caused by an increase in turbulence with height, combined with
anisotropy. The comparison of the Doppler widths derived for Ca ii with
results previously obtained for the X 10830 line of He I supports the
hypothesis that the chromosphere is heterogeneous and is composed of
regions of quite different physical properties.
---------------------------------------------------------
Title: The Profile of Hα during the Limb Flare of February 10, 1956.
Authors: Goldberg, Leo; Mohler, Orren C.; Muller, Edith A.
1958ApJ...127..302G Altcode:
Profiles of the Ha line in a very bright loop prominence associated
with the great limb flare of February 10, 1956, show pronounced violet
asymmetries. Despite the fact that the centers of different profiles,
made at several points in the line on two different exposures, exhibit
relative Doppler displacements as high as 0.8 A, the shapes of all
the profiles can be accounted for by the superposition on the main Ha
profile of an additional component centered between 1.5 and 2.0 A to
the violet. The possibility is discussed that the asymmetry may have
been caused by the presence of abnormal amounts of deuterium, presumably
generated by nuclear reactions during the flare event. It is concluded
that, although the evidence for deuterium is not conclusive, it would be
extremely important to observe other similar flareassociated prominences
in the future, with modern high-dispersion spectrographs. Observations
should also be made simultaneously on at least one additional line of
an element other than hydrogen, in order to eliminate velocity effects.
---------------------------------------------------------
Title: The chemical composition of the solar atmosphere.
Authors: Goldberg, Leo; Muller, Edith A.; Aller, Lawrence H.
1957AJ.....62R..15G Altcode:
The abundances of some 40 elements relative to hydrogen have been
redetermined in a new investigation of the chemical composition of
the solar atmosphere from the Fraunhofer spectrum. The measi~irements
of equivalent widths by the Utrecht group and by Allen's have been
supplemented by infrared data and by measurements of selected lines on
vacuum spectrograph plates from the McMath-Hulbert Observatory. The
method of analysis is that of weighting functions, as developed by
Minnaert and Claas for weak lines and by Pecker for lines of medium
strength. In this method, the equivalent width of each line is related
to the abundance by an integral over the model atmosphere, in which
the integrand is the product of the number of absorbing atoms, the
weighting function at each point in the atmosphere, and a so-called
saturation function which reduces to unity for weak lines. Special
numerical techniques for the evaluation of these integrals have been
devised by Elste and adapted by him for computation with the Michigan
high-speed computers, MIDAC and the IBM 650. An extensive set of these
integrals has been tabulated by Elste for both weak lines and those of
medium strength covering the wave-length region XX4ooo to 22,000 and
a wide range of excitation potentials. This tabulation has provided
the basis for the present investigation of solar abundances. The
model atmosphere employed was derived by Waddell and Pierce from the
latter's recent observations of solar-limb darkening and spectral-
energy distribution, but with the pressure distribution modified
by Elste in accordance with the work of Weidemann. The results are
generally in good agreement with those of other workers, but there
are notable exceptions, especially for those abundances that depend
on the analysis of lines of medium strength. The reason appears to be
that the shape of the curve of growth in the transition region differs
markedly for lines originating at different depths in the atmosphere. It
is anticipated that the results quoted here can be further improved
when new photoelectric observations of weak lines are secured with
the vacuum spectrograph of the McMath-Hulbert Observatory. However,
for a large number of elements, uncertainties in the f-values present
the major obstacle to definitive abundance determinations. University
of Michigan, Ann Arbor, Mich.
---------------------------------------------------------
Title: The origin of the double reversal in the Fraunhofer H and
K lines.
Authors: Goldberg, Leo; Muller, Edith A.
1957AJ.....62R..92G Altcode:
The discovery by 0. C. Wilson of a correlation between the absolute
magnitudes of the G, K and M stars and the widths of the emission
reversals in their K-line cores emphasizes the importance of
establishing the mechanism both for widening the H and K emission-line
cores in the sun and for producing the central self-reversal. Evidence
is presented that favors Doppler broadening on the one hand and
abundance broadening on the other. It is shown that the apparently
conflicting arguments for the two kinds of broadening can be resolved
if the cores of the H and K lines are formed in an optically-thick
chromosphere in which the excitation temperature decreases with
height. Methods are developed for the derivation of the excitation
temperature and Ca+ density distributions from the observed profiles and
it is shown that the resulting model accounts satisfactorily for the
main features of the observed profiles both at the center of the disk
and at the limb. University of Michigan Observatory, Ann Arbor, Mich.
---------------------------------------------------------
Title: The Abundances of the Elements in the Sun
Authors: Goldberg, Leo; Aller, Lawrence H.; Müller, Edith A.
1955stat.conf..141G Altcode: 1954stat.conf..141G
No abstract at ADS
---------------------------------------------------------
Title: Dreifarben-Photometrie des offenen Sternhaufens NGC 7510 und
seiner Umgebung. Mit 10 Textabbildungen.
Authors: Becker, W.; Müller, E. A.; Stenlin, U.
1955ZA.....38...81B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Dreifarben-Photometrie des offenen Sternhaufens NGC 654 und
einer benachbarten Sterngruppe. Mit 5 Textabbildungen
Authors: Müller, E. A.
1955ZA.....38..110M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Width of Hα in Solar Flares.
Authors: Goldberg, Leo; Dodson, Helen W.; Müller, Edith A.
1954ApJ...120...83G Altcode:
It is shown that the observed large widening, at or near maximum,
of the Ha emission line in certain solar flares can be explained as a
consequence of radiation damping and the high abundance of two- quantum
H atoms in the line of sight. When the effective width `of the Ha line
is calculated according to the theory of self-absorption, the assumption
of radiation damping leads to agreement with the observed lines widths
when the number of two-quantum H atoms lies in the approximate range per
cm2 in the line of sight. If it is assumed that the lateral extension
of a flare is large compared with its thick- ness, the theory predicts
that the effective width of Ha should be proportional to the square
root of sec 0, where 0 is the angular distance from the center of the
solar disk. Study of the Ha line widths of 610 flares reported in the
Quarterly Bulletin of the I.A.U. for the period January, 1949, through
June, 1952, reveals that the average line width increases steadily
with increasing central meridian distance of the flares. Furthermore,
flares with exceptionally wide lines ( 4.0 A) are observed most often
in flares 45 or more from the central meridian. The relation between
effective line width and central intensity found by Ellison is explained
as primarily a consequence of self-absorption. Finally, the existing
observational evidence in favor of the Stark effect as an important
cause of the line broadening is examined and found unconvincing.
---------------------------------------------------------
Title: Carbon Monoxide in the Sun.
Authors: Goldberg, Leo; Müller, Edith A.
1953ApJ...118..397G Altcode:
Nearly 300 llnes of carbon monoxide have been identified in the spectrum
of the solar limb between 2.29 and 2.50 . The lines belong to the
overtone bands 24), 31, 42, 33, , and 7-5. Analysis of the solar wave
lengths has led to a new determination of the vibrational and rotational
constants of the CO molecule. The measured absorption coefficients
of Penner and Weber and the theoretical values of Scholz have been
applied to the measured equivalent widths at the center of the disk. The
resulting equivalent abundance of CO is 1.45 X t0' molecules per square
centimeter above the photosphere, and the excitation temperature is
4300 K. It is shown from model-atmosphere calculations that solar Co is
concentrated near the top of the photosphere and hence that the derived
excitation temperature is consistent since it agrees with the boundary
temperature. At present, it is not known whether the dissociation
energy of CO is 9.6 or 11.1 e.v. If the lower value is correct, the
solar-line intensities suggest that the boundary temperature is less
than 4500 K. The exact value of the temperature depends on the choice of
atomic abundances for 0 and C. The low intensities of the fundamental
band lines of CO in the 4.6 region are explained as a consequence of
(1) the high opacity of the solar atmosphere at long wave lengths,
(2) the importance of stimulated emissions in the infrared, and (3)
the small collisional line widths in the sun's outer layers.
