piskunov

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Author name code: piskunov
ADS astronomy entries on 2022-09-14
author:"Piskunov, Nikolai"

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Title: Evolution of brightness and magnetic features of young
solar-type stars - I. The young G star HIP 89829
Authors: Perugini, G. M.; Marsden, S. C.; Waite, I. A.; Jeffers,
S. V.; Piskunov, N.; Shaw, N.; Burton, D. M.; Mengel, M. W.; Hughes,
J. E.; Hébrard, E. M.
2021MNRAS.508.3304P Altcode: 2021MNRAS.tmp.2515P
The evolution in latitude of sunspots is a key feature of the cyclic
solar dynamo. Here, we present the results of a spectroscopic and
spectropolarimetric monitoring campaign on the young (~20 Myr old)
early G star HIP 89829, in order to investigate potential evolution
in the distribution of the star's spots and magnetic features. Our
analysis of this G5V star spans eight epochs, from June 2010 to August
2015. The techniques of Doppler imaging and Zeeman-Doppler imaging were
used to create brightness maps for each epoch and magnetic maps for
two epochs. The brightness images show the star to have stable spot
features with two main spot latitudes - a polar spot, often seen on
young rapidly rotating stars such as this, and another highly unusual
group of large spot features around the 20° and 30° latitudes. These
lower spot latitudes appear to be rather stable over the 5 yr of
observations. We included a solar-type differential rotation law into
the imaging process and measured near-solid-body rotation for epochs
where sufficient data exist for this analysis. The magnetic features
show a dominant poloidal and a weaker toroidal magnetic field for both
Stokes V epochs, which is unusual for a star with a rapid rotation
period of 0.57 d. We conclude that HIP 89829 is an active young
solar-type star with long-lived spots and near-solid-body rotation.

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Title: HIRES, the High-resolution Spectrograph for the ELT
Authors: Marconi, A.; Abreu, M.; Adibekyan, V.; Aliverti, M.; Allende
Prieto, C.; Amado, P.; Amate, M.; Artigau, E.; Augusto, S.; Barros,
S.; Becerril, S.; Benneke, B.; Bergin, E.; Berio, P.; Bezawada,
N.; Boisse, I.; Bonfils, X.; Bouchy, F.; Broeg, C.; Cabral, A.;
Calvo-Ortega, R.; Canto Martins, B. L.; Chazelas, B.; Chiavassa,
A.; Christensen, L.; Cirami, R.; Coretti, I.; Covino, S.; Cresci,
G.; Cristiani, S.; Cunha Parro, V.; Cupani, G.; de Castro Leão,
I.; Renan de Medeiros, J.; Furlande Souza, M. A.; Di Marcantonio,
P.; Di Varano, I.; D'Odorico, V.; Doyon, R.; Drass, H.; Figueira,
P.; Belen Fragoso, A.; Uldall Fynbo, J. P.; Gallo, E.; Genoni,
M.; González Hernández, J.; Haehnelt, M.; Hlavacek-Larrondo, J.;
Hughes, I.; Huke, P.; Humphrey, A.; Kjeldsen, H.; Korn, A.; Kouach,
D.; Landoni, M.; Liske, J.; Lovis, C.; Lunney, D.; Maiolino, R.; Malo,
L.; Marquart, T.; Martins, C.; Mason, E.; Molaro, P.; Monnier, J.;
Monteiro, M.; Mordasini, C.; Morris, T.; Mucciarelli, A.; Murray,
G.; Niedzielski, A.; Nunes, N.; Oliva, E.; Origlia, L.; Pallé,
E.; Pariani, G.; Parr-Burman, P.; Peñate, J.; Pepe, F.; Pinna,
E.; Piskunov, N.; Rasilla Piñeiro, J. L.; Rebolo, R.; Rees, P.;
Reiners, A.; Riva, M.; Romano, D.; Rousseau, S.; Sanna, N.; Santos,
N.; Sarajlic, M.; Shen, T. -C.; Sortino, F.; Sosnowska, D.; Sousa,
S.; Stempels, E.; Strassmeier, K.; Tenegi, F.; Tozzi, A.; Udry,
S.; Valenziano, L.; Vanzi, L.; Weber, M.; Woche, M.; Xompero, M.;
Zackrisson, E.; Zapatero Osorio, M. R.
2021Msngr.182...27M Altcode: 2020arXiv201112317M
HIRES will be the high-resolution spectrograph at optical and
near-infrared (NIR) wavelengths for ESO's Extremely Large Telescope
(ELT). It will consist of three fibre-fed spectrographs providing a
wavelength coverage of 0.4-1.8 µm (with a goal of 0.35-1.8 µm) at a
spectral resolution of ~ 100 000. Fibre-feeding allows HIRES to have
several interchangeable observing modes, including a single-conjugate
adaptive optics (SCAO) module and a small diffraction-limited integral
field unit in the NIR. It will therefore be able to operate in both
seeing- and diffraction-limited modes. HIRES will address a wide range
of science cases spanning nearly all areas of research in astrophysics
and even fundamental physics. Some of the top science cases will be
the detection of biosignatures from exoplanet atmospheres, finding the
fingerprints of the first generation of stars (Pop III), tests on the
stability of Nature's fundamental couplings, and the direct detection
of the cosmic acceleration. The HIRES consortium is composed of more
than 30 institutes from 14 countries, forming a team of more than 200
scientists and engineers.

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Title: Accurate Short-Characteristics Radiative Transfer in A
Numerical Tool for Astrophysical RESearch (ANTARES)
Authors: Kostogryz, Nadiia M.; Kupka, Friedrich; Piskunov, Nikolai;
Fabbian, Damian; Krüger, Daniel; Gizon, Laurent
2021SoPh..296...46K Altcode:
We aim to improve the accuracy of radiative energy transport in
three-dimensional radiation hydrodynamical simulations in ANTARES
(A Numerical Tool for Astrophysical RESearch). We implement in the
ANTARES short-characteristics numerical schemes a modification of
the Bézier interpolant solver. This method yields a smoother surface
structure in simulations of solar convection and reduces the artifacts
appearing due to the limited number of rays along which the integration
is done. Reducing such artifacts leads to increased stability of the
code. We show that our new implementation achieves a better agreement
of the temperature structure and its gradient with a semi-empirical
model derived from observations, as well as of synthetic spectral-line
profiles with the observed solar spectrum.

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Title: Optimal extraction of echelle spectra: Getting the most out
of observations
Authors: Piskunov, Nikolai; Wehrhahn, Ansgar; Marquart, Thomas
2021A&A...646A..32P Altcode: 2020arXiv200805827P
Context. The price of instruments and observing time on modern
telescopes is quickly increasing. Therefore, it is worth revisiting
the data reduction algorithms to extract every bit of scientific
information from available observations. Echelle spectrographs
are typical instruments used in high-resolution spectroscopy, but
attempts to improve the wavelength coverage and versatility of these
instruments has resulted in a complicated and variable footprint of
the entrance slit projection onto the science detector. Traditional
spectral extraction methods generally fail to perform a truly optimal
extraction when the slit image is not aligned with the detector
columns and, instead, is tilted or even curved. Aims: Here, we
present the mathematical algorithms and examples of their application
to the optimal extraction and the following reduction steps for echelle
spectrometers equipped with an entrance slit that is imaged with various
distortions. The new method minimises the loss of spectral resolution,
maximises the signal-to-noise ratio, and efficiently identifies local
outliers. In addition to the new optimal extraction, we present order
splicing and a more robust continuum normalisation algorithm. 
Methods: We developed and implemented new algorithms that create a
continuum-normalised spectrum. In the process, we account for the
(variable) tilt or curvature of the slit image on the detector and
achieve optimal extraction without prior assumptions about the slit
illumination. Thus, the new method can handle arbitrary image slicers,
slit scanning, and other observational techniques aimed at increasing
the throughput or dynamic range. Results: We compare our methods
with other techniques for different instruments to illustrate the
superior performance of the new algorithms compared to commonly used
procedures. Conclusions: Advanced modelling of the focal plane
requires significant computational effort but it has proven worthwhile
thanks to the retrieval of a greater store of science information
from every observation. The described algorithms and tools are freely
available as part of our PyReduce package.

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Title: ELT-HIRES, the high resolution spectrograph for the ELT:
the Phase A study and the path to construction
Authors: Marconi, A.; Abreu, M.; Adibekyan, V.; Aliverti, M.; Allende
Prieto, C.; Amado, P.; Amate, M.; Artigau, E.; Augusto, S.; Barros, S.;
Becerril, S.; Benneke, B.; Bergin, E.; Berio, P.; Bezawada, N.; Boisse,
I.; Bonfils, X.; Bouchy, F.; Broeg, C.; Cabral, A.; Calvo-Ortega,
R.; Canto Martins, B. L.; Chazelas, B.; Chiavassa, A.; Christensen,
L.; Cirami, R.; Coretti, I.; Covino, S.; Cresci, G.; Cristiani, S.;
Cunha Parro, V.; Cupani, G.; D'Odorico, V.; de Castro Leão, I.;
de Medeiros, J. R.; de Souza, M.; Di Marcantonio, P.; Di Varano, I.;
Doyon, R.; Drass, H.; Figueira, P.; Fragoso, A.; Fynbo, J.; Gallo,
E.; Genoni, M.; González Hernández, J.; Gratton, R.; Haehnelt, M.;
Hansen, C.; Hlavacek-Larrondo, J.; Hughes, I.; Huke, P.; Humphrey,
A.; Kjeldsen, H.; Korn, A.; Kouach, D.; Landoni, M.; Liske, J.;
Lovis, C.; Lunney, D.; Maiolino, R.; Malo, L.; Marquart, T.; Martins,
C. J. A. P.; Maslowski, P.; Mason, E.; Micela, G.; Molaro, P.; Monnier,
J.; Monteiro, M.; Mordasini, C.; Morris, T.; Mucciarelli, A.; Murray,
G.; Niedzielski, A.; Niemczura, E.; Nisini, B.; Nunes, N.; Oliva,
E.; Origlia, L.; Pallé, E.; Pariani, G.; Parr-Burman, P.; Pasquini,
L.; Peñate, J.; Pepe, F.; Pietrzynski, G.; Pinna, E.; Piskunov,
N.; Pollo, A.; Rasilla, J.; Rebolo, R.; Rees, P.; Reiners, A.; Riva,
M.; Romano, D.; Rousseau, S.; Sanna, N.; Sarajlic, M.; Shen, T. -C.;
Sortino, F.; Sosnowska, D.; Sousa, S.; Stempels, E.; Strassmeier, K.;
Tenegi, F.; Tozzi, A.; Udry, S.; Valenziano, L.; Vanzi, L.; Weber,
M.; Woche, M.; Xompero, M.; Zackrisson, E.; Zapatero Osorio, M. R.
2020SPIE11447E..26M Altcode:
HIRES is the high-resolution spectrograph of the European Extremely
Large Telescope at optical and near-infrared wavelengths. It consists
of three fibre-fed spectrographs providing a wavelength coverage of
0.4-1.8 µm (goal 0.35-2.4 µm) at a spectral resolution of 100,000. The
fibre-feeding allows HIRES to have several, interchangeable observing
modes including a SCAO module and a small diffraction-limited IFU
in the NIR. Therefore, it will be able to operate both in seeing-
and diffraction-limited modes. Its modularity will ensure that HIRES
can be placed entirely on the Nasmyth platform, if enough mass and
volume is available, or part on the Nasmyth and part in the Coud`e
room. ELT-HIRES has a wide range of science cases spanning nearly all
areas of research in astrophysics and even fundamental physics. Among
the top science cases there are the detection of biosignatures from
exoplanet atmospheres, finding the fingerprints of the first generation
of stars (PopIII), tests on the stability of Nature's fundamental
couplings, and the direct detection of the cosmic acceleration. The
HIRES consortium is composed of more than 30 institutes from 14
countries, forming a team of more than 200 scientists and engineers.

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Title: Shine BRITE: shedding light on stellar variability through
advanced models
Authors: Fabbian, D.; Kupka, F.; Krüger, D.; Kostogryz, N. M.;
Piskunov, N.
2020svos.conf..155F Altcode: 2020arXiv200201560F
The correct interpretation of the large amount of complex data from
next-generation (in particular, space-based) observational facilities
requires a very strong theoretical underpinning. One can predict
that, in the near future, the use of atmospheric models obtained with
three-dimensional (3-D) radiation magneto-hydrodynamics (RMHD) codes,
coupled with advanced radiative transfer treatment including non-local
thermodynamic equilibrium (non-LTE) effects and polarisation, will
become the norm. In particular, stellar brightness variability in cool
stars (i.e., spectral types F-- M) can be caused by several different
effects besides pulsation. In this review we have briefly discussed
some published results, and mentioned aspects of recent progress. It
then attempted to peek into what the future may hold for understanding
this important aspect of the lives of stars.

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Title: Hyperfine Splitting in the VALD Database of Spectral-line
Parameters
Authors: Pakhomov, Yu. V.; Ryabchikova, T. A.; Piskunov, N. E.
2019ARep...63.1010P Altcode: 2019arXiv191103189P
The Vienna Atomic Line Database (VALD) has been supplemented with new
data and new functionality—the possibility of taking into account the
effect of hyperfine splitting (HFS) of atomic levels in the analysis of
line profiles. This has been done through the creation of an ancillary
SQL database with the HFS constants for atomic levels of 58 isotopes of
30 neutral and singly-ionized atoms. The completeness of the collected
data and new opportunities for studies of stars of various spectral
types is analyzed. The database enables analysis of splitting of up to
60% of lines with measurable effects in the ultraviolet (λ ≳ 1000
Å ), and up to 100% of such lines in the optical and infrared ranges
(λ ≲ 25 000 Å ) for A-M stars. In the spectra of hot O-B stars,
it is necessary to use laboratory measurements for atoms in the second
and higher stages of ionization.

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Title: Evaluation of the Recent Atomic Data for Fe uc(i) Lines Based
on Solar and Stellar Spectra
Authors: Ryabchikova, T.; Piskunov, N.; Sitnova, T.
2019SoPh..294..156R Altcode:
We performed an extensive comparative analysis of the recent
experimental data on Fe I transition probabilities (TP) based on the
observed solar and stellar spectra. This work is part of the Vienna
Atomic Line database (VALD) activities. Our motivation is to keep
the VALD line list as complete as possible and provide VALD users
with substantiated recommendations for the most accurate atomic
data. For assessment of data quality we choose the "normal" (as
opposed to peculiar and/or magnetic) Main Sequence sharp-line stars
of different effective temperatures with accurately known atmospheric
parameters: Sun, Procyon, HD 32115, and 21 Peg. Theoretical spectra of
these stars were synthesized for 1D plane-parallel model atmospheres
accounting for non-local thermodynamic equilibrium (NLTE) effects,
and then they were compared with the observations. For all of the
stars we derived atmospheric abundances based on the new and previous
experimental TP. When using the new TPs the best agreement for iron
is achieved with the TP of the Hannover group (Bard, Kock, and Kock,
Astron. Astrophys.248, 315, 1991; Bard and Kock, Astron. Astrophys.282,
1014, 1994). The Hannover set is recommended as the primary source
of transition probabilities in stellar abundance analysis. The new
TP data significantly increase the number of spectral lines of Fe
I in the optical and red spectral regions available for accurate
abundance analysis of stars in a wide range of temperatures and
metallicities. Comparison with the observed stellar spectra invalidates
some new experimental data despite the small given uncertainty of the
laboratory measurements. Finally, we note the importance of accurate
line-broadening data.

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Title: Model-free inverse method for transit imaging of stellar
surfaces. Using transit surveys to map stellar spot coverage
Authors: Aronson, Erik; Piskunov, Nikolai
2019A&A...630A.122A Altcode: 2019arXiv190206555A
Context. We present a model-free method for mapping surface brightness
variations. Aims: We aim to develop a method that is not
dependent on either stellar atmosphere models or limb-darkening
equation. This method is optimized for exoplanet transit surveys such
that a large database of stellar spot coverage can be created. 
Methods: The method uses light curves from several transit events of the
same system. These light curves are phase-folded and median-combined
to for a high-quality light curve without temporal local brightness
variations. Stellar specific intensities are extracted from this light
curve using a model-free method. We search individual light curves
for departures from the median-combined light curve. Such departures
are interpreted as brightness variations on the stellar surface. A
map of brightness variations on the stellar surface is produced by
finding the brightness distribution that can produce a synthetic light
curve that fits observations well. No assumptions about the size,
shape, or contrast of brightness variations are made. Results:
We successfully reproduce maps of stellar disks from both synthetic
data and archive observations from FORS2, the visual and near UV FOcal
Reducer and low dispersion Spectrograph for the Very Large Telescope
(VLT).

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Title: Spot evolution on LQ Hya from 2006-2017: temperature maps
based on SOFIN and FIES data
Authors: Cole-Kodikara, Elizabeth M.; Käpylä, Maarit J.; Lehtinen,
Jyri J.; Hackman, Thomas; Ilyin, Ilya V.; Piskunov, Nikolai;
Kochukhov, Oleg
2019A&A...629A.120C Altcode: 2019arXiv190408713C
Context. LQ Hya is one of the most frequently studied young solar
analogue stars. Recently, it has been observed to show intriguing
behaviour when analysing long-term photometry. For instance, from
2003-2009, a coherent spot structure migrating in the rotational
frame was reported by various authors. However, ever since, the
star has entered a chaotic state where coherent structures seem to
have disappeared and rapid phase jumps of the photometric minima
occur irregularly over time. Aims: LQ Hya is one of the stars
included in the SOFIN/FIES long-term monitoring campaign extending
over 25 yr. Here, we publish new temperature maps for the star during
2006-2017, covering the chaotic state of the star. Methods:
We used a Doppler imaging technique to derive surface temperature
maps from high-resolution spectra. Results: From the mean
temperatures of the Doppler maps, we see a weak but systematic increase
in the surface temperature of the star. This is consistent with the
simultaneously increasing photometric magnitude. During nearly all
observing seasons, we see a high-latitude spot structure which is
clearly non-axisymmetric. The phase behaviour of this structure is very
chaotic but agrees reasonably well with the photometry. Equatorial spots
are also frequently seen, but we interpret many of them to be artefacts
due to the poor to moderate phase coverage. Conclusions: Even
during the chaotic phase of the star, the spot topology has remained
very similar to the higher activity epochs with more coherent and
long-lived spot structures. In particular, we see high-latitude and
equatorial spot activity, the mid latitude range still being most often
void of spots. We interpret the erratic jumps and drifts in phase of
the photometric minima to be caused by changes in the high-latitude spot
structure rather than the equatorial spots. Based on observations
made with the Nordic Optical Telescope, operated by the Nordic Optical
Telescope Scientific Association at the Observatorio del Roque de los
Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias.

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Title: Starspot activity of HD 199178. Doppler images from 1994-2017
Authors: Hackman, T.; Ilyin, I.; Lehtinen, J. J.; Kochukhov, O.;
Käpylä, M. J.; Piskunov, N.; Willamo, T.
2019A&A...625A..79H Altcode: 2018arXiv181202013H
Context. Studying the spots of late-type stars is crucial for
distinguishing between the various proposed dynamo mechanisms
believed to be the main cause of starspot activity. For this research
it is important to collect observation time series that are long
enough to unravel both long- and short-term spot evolution. Doppler
imaging is a very efficient method for studying spots of stars that
cannot be angularly resolved. Aims: High-resolution spectral
observations during 1994-2017 are analysed in order to reveal long-
and short-term changes in the spot activity of the FK Comae-type
subgiant HD 199178. Methods: Most of the observations were
collected with the Nordic Optical Telescope. The Doppler imaging
temperature maps were calculated using an inversion technique based on
Tikhonov regularisation and utilising multiple spectral lines. 
Results: We present a unique series of 41 temperature maps spanning
more than 23 years. All reliable images show a large cool spot region
centred near the visible rotation pole. Some lower latitude cool
features are also recovered, although the reliability of these is
questionable. There is an expected anti-correlation between the mean
surface temperature and the spot coverage. Using the Doppler images,
we construct the equivalent of a solar butterfly diagram for HD
199178. Conclusions: HD 199178 clearly has a long-term large
and cool spot structure at the rotational pole. This spot structure
dominated the spot activity during the years 1994-2017. The size
and position of the structure has evolved with time, with a gradual
increase during the last years. The lack of lower latitude features
prevents the determination of a possible differential rotation. The spectra 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/qcat?J/A+A/625/A79">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/625/A79</A>Based
on observations made with the Nordic Optical Telescope, operated by the
Nordic Optical Telescope Scientific Association at the Observatorio
del Roque de los Muchachos, La Palma, Spain, of the Instituto de
Astrofisica de Canarias.

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Title: VizieR Online Data Catalog: HD199178 1994-2017 spectra
(Hackman+, 2019)
Authors: Hackman, T.; Ilyin, I.; Lehtinen, J. J.; Kochukhov, O.;
Kaepylae, M. J.; Piskunov, N.; Willamo, T.
2019yCat..36250079H Altcode:
The instruments used where the Rozhen high resolution spectrograph
(R=35000), SOFIN (R=80000, R=1400000) and FIES (R=67000). Observation
times and S/N-ratios are given in the log-file. The spectral regions
used for Doppler images varied with the instruments and seasons. The
regions were centred around the following wavelengths (in Angstroms):
6265, 6411, 6431, 6439 6644, 6663 and 7511. (2 data files).

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Title: 4MOST: Project overview and information for the First Call
for Proposals
Authors: de Jong, R. S.; Agertz, O.; Berbel, A. A.; Aird, J.;
Alexander, D. A.; Amarsi, A.; Anders, F.; Andrae, R.; Ansarinejad,
B.; Ansorge, W.; Antilogus, P.; Anwand-Heerwart, H.; Arentsen, A.;
Arnadottir, A.; Asplund, M.; Auger, M.; Azais, N.; Baade, D.; Baker,
G.; Baker, S.; Balbinot, E.; Baldry, I. K.; Banerji, M.; Barden,
S.; Barklem, P.; Barthélémy-Mazot, E.; Battistini, C.; Bauer, S.;
Bell, C. P. M.; Bellido-Tirado, O.; Bellstedt, S.; Belokurov, V.;
Bensby, T.; Bergemann, M.; Bestenlehner, J. M.; Bielby, R.; Bilicki,
M.; Blake, C.; Bland-Hawthorn, J.; Boeche, C.; Boland, W.; Boller,
T.; Bongard, S.; Bongiorno, A.; Bonifacio, P.; Boudon, D.; Brooks,
D.; Brown, M. J. I.; Brown, R.; Brüggen, M.; Brynnel, J.; Brzeski,
J.; Buchert, T.; Buschkamp, P.; Caffau, E.; Caillier, P.; Carrick,
J.; Casagrande, L.; Case, S.; Casey, A.; Cesarini, I.; Cescutti, G.;
Chapuis, D.; Chiappini, C.; Childress, M.; Christlieb, N.; Church, R.;
Cioni, M. -R. L.; Cluver, M.; Colless, M.; Collett, T.; Comparat, J.;
Cooper, A.; Couch, W.; Courbin, F.; Croom, S.; Croton, D.; Daguisé,
E.; Dalton, G.; Davies, L. J. M.; Davis, T.; de Laverny, P.; Deason,
A.; Dionies, F.; Disseau, K.; Doel, P.; Döscher, D.; Driver, S. P.;
Dwelly, T.; Eckert, D.; Edge, A.; Edvardsson, B.; Youssoufi, D. E.;
Elhaddad, A.; Enke, H.; Erfanianfar, G.; Farrell, T.; Fechner, T.;
Feiz, C.; Feltzing, S.; Ferreras, I.; Feuerstein, D.; Feuillet, D.;
Finoguenov, A.; Ford, D.; Fotopoulou, S.; Fouesneau, M.; Frenk, C.;
Frey, S.; Gaessler, W.; Geier, S.; Gentile Fusillo, N.; Gerhard,
O.; Giannantonio, T.; Giannone, D.; Gibson, B.; Gillingham, P.;
González-Fernández, C.; Gonzalez-Solares, E.; Gottloeber, S.; Gould,
A.; Grebel, E. K.; Gueguen, A.; Guiglion, G.; Haehnelt, M.; Hahn, T.;
Hansen, C. J.; Hartman, H.; Hauptner, K.; Hawkins, K.; Haynes, D.;
Haynes, R.; Heiter, U.; Helmi, A.; Aguayo, C. H.; Hewett, P.; Hinton,
S.; Hobbs, D.; Hoenig, S.; Hofman, D.; Hook, I.; Hopgood, J.; Hopkins,
A.; Hourihane, A.; Howes, L.; Howlett, C.; Huet, T.; Irwin, M.; Iwert,
O.; Jablonka, P.; Jahn, T.; Jahnke, K.; Jarno, A.; Jin, S.; Jofre,
P.; Johl, D.; Jones, D.; Jönsson, H.; Jordan, C.; Karovicova, I.;
Khalatyan, A.; Kelz, A.; Kennicutt, R.; King, D.; Kitaura, F.; Klar,
J.; Klauser, U.; Kneib, J. -P.; Koch, A.; Koposov, S.; Kordopatis, G.;
Korn, A.; Kosmalski, J.; Kotak, R.; Kovalev, M.; Kreckel, K.; Kripak,
Y.; Krumpe, M.; Kuijken, K.; Kunder, A.; Kushniruk, I.; Lam, M. I.;
Lamer, G.; Laurent, F.; Lawrence, J.; Lehmitz, M.; Lemasle, B.; Lewis,
J.; Li, B.; Lidman, C.; Lind, K.; Liske, J.; Lizon, J. -L.; Loveday,
J.; Ludwig, H. -G.; McDermid, R. M.; Maguire, K.; Mainieri, V.; Mali,
S.; Mandel, H.; Mandel, K.; Mannering, L.; Martell, S.; Martinez
Delgado, D.; Matijevic, G.; McGregor, H.; McMahon, R.; McMillan,
P.; Mena, O.; Merloni, A.; Meyer, M. J.; Michel, C.; Micheva, G.;
Migniau, J. -E.; Minchev, I.; Monari, G.; Muller, R.; Murphy, D.;
Muthukrishna, D.; Nandra, K.; Navarro, R.; Ness, M.; Nichani, V.;
Nichol, R.; Nicklas, H.; Niederhofer, F.; Norberg, P.; Obreschkow, D.;
Oliver, S.; Owers, M.; Pai, N.; Pankratow, S.; Parkinson, D.; Paschke,
J.; Paterson, R.; Pecontal, A.; Parry, I.; Phillips, D.; Pillepich,
A.; Pinard, L.; Pirard, J.; Piskunov, N.; Plank, V.; Plüschke, D.;
Pons, E.; Popesso, P.; Power, C.; Pragt, J.; Pramskiy, A.; Pryer,
D.; Quattri, M.; Queiroz, A. B. d. A.; Quirrenbach, A.; Rahurkar,
S.; Raichoor, A.; Ramstedt, S.; Rau, A.; Recio-Blanco, A.; Reiss, R.;
Renaud, F.; Revaz, Y.; Rhode, P.; Richard, J.; Richter, A. D.; Rix,
H. -W.; Robotham, A. S. G.; Roelfsema, R.; Romaniello, M.; Rosario, D.;
Rothmaier, F.; Roukema, B.; Ruchti, G.; Rupprecht, G.; Rybizki, J.;
Ryde, N.; Saar, A.; Sadler, E.; Sahlén, M.; Salvato, M.; Sassolas,
B.; Saunders, W.; Saviauk, A.; Sbordone, L.; Schmidt, T.; Schnurr,
O.; Scholz, R. -D.; Schwope, A.; Seifert, W.; Shanks, T.; Sheinis,
A.; Sivov, T.; Skúladóttir, Á.; Smartt, S.; Smedley, S.; Smith,
G.; Smith, R.; Sorce, J.; Spitler, L.; Starkenburg, E.; Steinmetz,
M.; Stilz, I.; Storm, J.; Sullivan, M.; Sutherland, W.; Swann, E.;
Tamone, A.; Taylor, E. N.; Teillon, J.; Tempel, E.; ter Horst, R.;
Thi, W. -F.; Tolstoy, E.; Trager, S.; Traven, G.; Tremblay, P. -E.;
Tresse, L.; Valentini, M.; van de Weygaert, R.; van den Ancker, M.;
Veljanoski, J.; Venkatesan, S.; Wagner, L.; Wagner, K.; Walcher,
C. J.; Waller, L.; Walton, N.; Wang, L.; Winkler, R.; Wisotzki, L.;
Worley, C. C.; Worseck, G.; Xiang, M.; Xu, W.; Yong, D.; Zhao, C.;
Zheng, J.; Zscheyge, F.; Zucker, D.
2019Msngr.175....3D Altcode: 2019arXiv190302464D
We introduce the 4-metre Multi-Object Spectroscopic Telescope (4MOST),
a new high-multiplex, wide-field spectroscopic survey facility under
development for the four-metre-class Visible and Infrared Survey
Telescope for Astronomy (VISTA) at Paranal. Its key specifications
are: a large field of view (FoV) of 4.2 square degrees and a high
multiplex capability, with 1624 fibres feeding two low-resolution
spectrographs (R = λ/Δλ 6500), and 812 fibres transferring light
to the high-resolution spectrograph (R 20 000). After a description of
the instrument and its expected performance, a short overview is given
of its operational scheme and planned 4MOST Consortium science; these
aspects are covered in more detail in other articles in this edition
of The Messenger. Finally, the processes, schedules, and policies
concerning the selection of ESO Community Surveys are presented,
commencing with a singular opportunity to submit Letters of Intent
for Public Surveys during the first five years of 4MOST operations.

---------------------------------------------------------
Title: VizieR Online Data Catalog: V-band differential photometry
for V889 Her (Willamo+, 2019)
Authors: Willamo, T.; Hackman, T.; Lehtinen, J. J.; Kapyla, M. J.;
Ilyin, I.; Henry, G. W.; Jetsu, L.; Kochukhov, O.; Piskunov, N.
2019yCat..36220170W Altcode:
We present the Johnson V-band differential photometry of V889 Her,
obtained with the Tennessee State University T3 0.4m Automatic
Photoelectric Telescope. The analysis of the data has been done
using the comparison star HD 171286; the V-magnitude of V889 Her
is gained by adding the V-magnitude of HD 171286 (V=6.84; Oja,
1987A&amp;AS...71..561O) to each data point. For further analysis
we use the Continous Period Search-method (CPS; Lehtinen et al.,
2011A&amp;A...527A.136L) to derive mean magnitudes for longer sets of
data. (1 data file).

---------------------------------------------------------
Title: Long-term spot monitoring of the young solar analogue V889
Herculis
Authors: Willamo, T.; Hackman, T.; Lehtinen, J. J.; Käpylä, M. J.;
Ilyin, I.; Henry, G. W.; Jetsu, L.; Kochukhov, O.; Piskunov, N.
2019A&A...622A.170W Altcode: 2018arXiv181105330W
Context. Starspots are important manifestations of stellar magnetic
activity. By studying their behaviour in young solar analogues, we can
unravel the properties of their magnetic cycles. This gives crucial
information of the underlying dynamo process. Comparisons with the
solar cycle enable us to infer knowledge about how the solar dynamo
has evolved during the Sun's lifetime. Aims: Here we study the
correlation between photometric brightness variations, spottedness, and
mean temperature in V889 Her, a young solar analogue. Our data covers
18 years of spectroscopic and 25 years of photometric observations. Methods: We use Doppler imaging to derive temperature maps from
high-resolution spectra. We use the Continuous Period Search method
to retrieve mean V-magnitudes from photometric data. Results:
Our Doppler imaging maps show a persistent polar spot structure
varying in strength. This structure is centred slightly off the
rotational pole. The mean temperature derived from the maps shows an
overall decreasing trend, as does the photometric mean brightness,
until it reaches its minimum around 2017. The filling factor of cool
spots, however, shows only a weak tendency to anti-correlate with the
decreasing mean brightness. Conclusions: We interpret V889 Her to
have entered into a grand maximum in its activity. The clear relation
between the mean temperature of the Doppler imaging surface maps and
the mean magnitude supports the reliability of the Doppler images. The
lack of correlation between the mean magnitude and the spottedness
may indicate that bright features in the Doppler images are real. Photometric data 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/qcat?J/A+A/622/A170">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/622/A170</A>Based
on observations made with the Nordic Optical Telescope, operated on
the island of La Palma jointly by Denmark, Finland, Iceland, Norway,
and Sweden, in the Spanish Observatorio del Roque de los Muchachos of
the Instituto de Astrofisica de Canarias. Based on observations made
with the HARPSpol instrument on the ESO 3.6m telescope at La Silla
(Chile), under the programme ID 091.D-0836.

---------------------------------------------------------
Title: VALD: The Meeting Point of Data Producers and Data Users
Authors: Ryabchikova, Tatiana; Pakhomov, Yury; Piskunov, Nikolai
2018Galax...6...93R Altcode:
Vienna Atomic Line Database (VALD) contains data on atomic and
molecular energy levels and parameters of spectral lines required
for stellar spectra analysis. Hundreds of millions of lines for fine
spectral synthesis and for opacity calculations are collected in the
present version of VALD (VALD3). Critical evaluation of the data and
the diversity of extraction tools support the high popularity of
VALD among users. The data model of VALD3 incorporates obligatory
links to the bibliography making our database more attractive as a
publishing platform for data producers. The VALD data quality and
completeness are constantly improving allowing better reproduction
of stellar spectra. To illustrate continuous evolution of the data
content we present a comparative analysis of the recent experimental and
theoretical atomic data for Fe-group elements, which will be included in
the next VALD release. This release will also include a possibility for
extracting the line data with full isotopic and hyperfine structures.

---------------------------------------------------------
Title: A unique infrared spectropolarimetric unit for CRIRES+
Authors: Piskunov, Nikolai; Stempels, Eric; Lavail, Alexis; Escuti,
Michael; Snik, Frans; Dolgopolov, Andrey; Rozel, Milan; Durandet,
Candice; Hatzes, Artie; Bristow, Paul; Brucalassi, Anna; Cumani,
Claudio; Dorn, Reinhold J.; Haimerl, Andreas; Heiter, Ulrike;
Hinterschuster, Renate; Follert, Roman; Ives, Derek; Jung, Yves;
Kerber, Florian; Klein, Barbara; Lizon, Jean-Louis; Marquart, Thomas;
Molina-Conde, Ignacio; Pasquini, Luca; Paufique, Jérôme; Oliva,
Ernesto; Reiners, Ansgar; Seemann, Ulf; Stegmeier, Jörg; Tordo,
Sebastien; Valenti, Elena
2018SPIE10702E..34P Altcode:
High-resolution infrared spectropolarimetry has many science
applications in astrophysics. One of them is measuring weak magnetic
fields using the Zeeman effect. Infrared domain is particularly
advantageous as Zeeman splitting of spectral lines is proportional
to the square of the wavelength while the intrinsic width of the
line cores increases only linearly. Important science cases include
detection and monitoring of global magnetic fields on solar-type
stars, study of the magnetic field evolution from stellar formation
to the final stages of the stellar life with massive stellar winds,
and the dynamo mechanism operation across the boundary between fully-
and partially-convective stars. CRIRES+ (the CRIRES upgrade project)
includes a novel spectropolarimetric unit (SPU) based on polar-
ization gratings. The novel design allows to perform beam-splitting
very early in the optical path, directly after the tertiary mirror
of the telescope (the ESO Very Large Telescope, VLT), minimizing
instrumental polariza- tion. The new SPU performs polarization
beam-splitting in the near-infrared while keeping the telescope beam
mostly unchanged in the optical domain, making it compatible with the
adaptive optics system of the CRIRES+ instrument. The SPU consists
of four beam-splitters optimized for measuring circular and linear
polarization of spectral lines in YJ and HK bands. The SPU can perform
beam switching allowing to correct for throughput in each beam and for
variations in detector pixel sensitivity. Other new features of CRIRES+,
such as substantially increased wavelength coverage, stability and
advanced data reduction pipeline will further enhance the sensitivity
of the polarimetric mode. The combination of the SPU, CRIRES+ and the
VLT is a unique facility for making major progress in understanding
stellar activity. In this article we present the design of the SPU,
laboratory measurements of individual components and of the whole unit
as well as the performance prediction for the operation at the VLT.

---------------------------------------------------------
Title: Analysis of the polarimetric performance of the HARPS3
Cassegrain adaptor unit
Authors: Dorval, Patrick; Snik, Frans; Piskunov, Nikolai; Navarro,
Ramon; Kragt, Jan; ter Horst, Rik; Kunst, Peter; Snellen, Ignas;
Naylor, Tim; Thompson, Samantha
2018SPIE10702E..6BD Altcode:
The third version of the High Accuracy Radial velocity Planet Searcher
(HARPS3) instrument is built for a ten-year programme aimed at achieving
10 cm/sec radial velocity precision on nearby stars to search for
Earth-like planets. HARPS3 will be commissioned on the to-be-roboticized
2.54-m Isaac Newton Telescope at La Palma in 2021. One of the main
changes compared to its predecessors is the novel dual-beam Cassegrain
focus, featuring a stabilised beam feed into the HARPS3 spectrograph
and an insertable polarimetric sub-unit. This polarimetric sub-unit
enables HARPS3 to directly measure stellar activity signatures,
which can be useful for correcting activity-induced radial velocity
jitter in the search for Earth-like planets. The sub-unit consists
of superachromatic polymer quarter- and half-wave retarders for
circular and linear polarizations respectively, designed to suppress
polarized fringing, and a novel polarimetric beam splitter based
on a wire-grid design, separating the two polarimetric beams by 30
mm and feeding two separate science fibers. The dual-beam exchange
implementation in combination with the extreme stability of the HARPS3
spectrograph enables a polarimetric sensitivity of 10-5
on bright stars. One of the main challenges of such a system is in the
characterization of instrumental polarization effects which limit the
polarimetric accuracy of the polarimetric observing mode. By design
and characterization of this subsystem and by pre-emptively mitigating
possible noise sources, we can minimize the noise characteristics of
the polarization sub-unit to allow for precise observations. In this
paper we report on the design, realization, assembly, alignment, and
testing of the polarimetric unit to be installed in the Cassegrain
Adaptor Unit of the HARPS3 spectrograph

---------------------------------------------------------
Title: Full system test and early preliminary acceptance Europe
results for CRIRES+
Authors: Brucalassi, Anna; Dorn, Reinhold J.; Follert, Roman;
Hatzes, Artie; Bristow, Paul; Seemann, Ulf; Cumani, Claudio;
Eschbaumer, Siegfried; Haimerl, Andreas; Haug, Marcus; Heiter, Ulrike;
Hinterschuster, Renate; Ives, Derek J.; Jung, Yves; Kerber, Florian;
Klein, Barbara; Lavail, Alexis; Lizon, Jean Louis; Marquart, Thomas;
Moins, Christophe; Molina-Conde, Ignacio; Oliva, Ernesto; Pasquini,
Luca; Paufique, Jérôme; Piskunov, Nikolai; Stegmeier, Jörg;
Stempels, Eric; Tordo, Sebastien; Valenti, Elena; Anwand-Heerwart,
Heiko; Hauptner, Katja; Jeep, Peter; Marvin, Christopher; Reiners,
Ansgar; Rhode, Petra; Schmidt, Christof; Umlauf, Tim
2018SPIE10702E..39B Altcode:
CRIRES+ is the new high-resolution NIR echelle spectrograph intended to
be operated at the platform B of VLT Unit telescope UT3. It will cover
from Y to M bands (0.95-5.3um) with a spectral resolution of R = 50000
or R=100000. The main scientific goals are the search of super-Earths
in the habitable zone of low-mass stars, the characterisation
of transiting planets atmosphere and the study of the origin and
evolution of stellar magnetic fields. Based on the heritage of the
old adaptive optics (AO) assisted VLT instrument CRIRES, the new
spectrograph will present improved optical layout, a new detector
system and a new calibration unit providing optimal performances in
terms of simultaneous wavelength coverage and radial velocity accuracy
(a few m/s). The total observing efficiency will be enhanced by a factor
of 10 with respect to CRIRES. An innovative spectro-polarimetry mode
will be also offered and a new metrology system will ensure very high
system stability and repeatability. Fiinally, the CRIRES+ project will
also provide the community with a new data reduction software (DRS)
package. CRIRES+ is currently at the initial phase of its Preliminary
Acceptance in Europe (PAE) and it will be commissioned early in 2019
at VLT. This work outlines the main results obtained during the initial
phase of the full system test at ESO HQ Garching.

---------------------------------------------------------
Title: ELT-HIRES, the high resolution spectrograph for the ELT:
results from the Phase A study
Authors: Marconi, A.; Allende Prieto, C.; Amado, P. J.; Amate, M.;
Augusto, S. R.; Becerril, S.; Bezawada, N.; Boisse, I.; Bouchy,
F.; Cabral, A.; Chazelas, B.; Cirami, R.; Coretti, I.; Cristiani,
S.; Cupani, G.; de Castro Leão, I.; de Medeiros, J. R.; de Souza,
M. A. F.; Di Marcantonio, P.; Di Varano, I.; D'Odorico, V.; Drass, H.;
Figueira, P.; Fragoso, A. B.; Fynbo, J. P. U.; Genoni, M.; González
Hernández, J. I.; Haehnelt, M.; Hughes, I.; Huke, P.; Kjeldsen,
H.; Korn, A. J.; Landoni, M.; Liske, J.; Lovis, C.; Maiolino, R.;
Marquart, T.; Martins, C. J. A. P.; Mason, E.; Monteiro, M. A.; Morris,
T.; Murray, G.; Niedzielski, A.; Oliva, E.; Origlia, L.; Pallé, E.;
Parr-Burman, P.; Parro, V. C.; Pepe, F.; Piskunov, N.; Rasilla, J. L.;
Rees, P.; Rebolo, R.; Riva, M.; Rousseau, S.; Sanna, N.; Santos, N. C.;
Shen, T. -C.; Sortino, F.; Sosnowska, D.; Sousa, S.; Stempels, E.;
Strassmeier, K.; Tenegi, F.; Tozzi, A.; Udry, S.; Valenziano, L.;
Vanzi, L.; Weber, M.; Woche, M.; Xompero, M.; Zackrisson, E.
2018SPIE10702E..1YM Altcode:
We present the results from the phase A study of ELT-HIRES, an
optical-infrared High Resolution Spectrograph for ELT, which has just
been completed by a consortium of 30 institutes from 12 countries
forming a team of about 200 scientists and engineers. The top science
cases of ELT-HIRES will be the detection of life signatures from
exoplanet atmospheres, tests on the stability of Nature's fundamental
couplings, the direct detection of the cosmic acceleration. However,
the science requirements of these science cases enable many other
groundbreaking science cases. The baseline design, which allows
to fulfil the top science cases, consists in a modular fiber- fed
cross-dispersed echelle spectrograph with two ultra-stable spectral
arms providing a simultaneous spectral range of 0.4-1.8 μm at a
spectral resolution of 100,000. The fiber-feeding allows ELT-HIRES to
have several, interchangeable observing modes including a SCAO module
and a small diffraction-limited IFU.

---------------------------------------------------------
Title: Model-independent Exoplanet Transit Spectroscopy
Authors: Aronson, Erik; Piskunov, Nikolai
2018AJ....155..208A Altcode: 2018arXiv180305327A
We propose a new data analysis method for obtaining transmission
spectra of exoplanet atmospheres and brightness variation across the
stellar disk from transit observations. The new method is capable
of recovering exoplanet atmosphere absorption spectra and stellar
specific intensities without relying on theoretical models of stars
and planets. We simultaneously fit both stellar specific intensity
and planetary radius directly to transit light curves. This allows
stellar models to be removed from the data analysis. Furthermore,
we use a data quality weighted filtering technique to achieve an
optimal trade-off between spectral resolution and reconstruction
fidelity homogenizing the signal-to-noise ratio across the wavelength
range. Such an approach is more efficient than conventional data
binning onto a low-resolution wavelength grid. We demonstrate that our
analysis is capable of reproducing results achieved by using an explicit
quadratic limb-darkening equation and that the filtering technique helps
eliminate spurious spectral features in regions with strong telluric
absorption. The method is applied to the VLT FORS2 observations of the
exoplanets GJ 1214 b and WASP-49 b, and our results are in agreement
with previous studies. Comparisons between obtained stellar specific
intensity and numerical models indicates that the method is capable of
accurately reconstructing the specific intensity. The proposed method
enables more robust characterization of exoplanetary atmospheres by
separating derivation of planetary transmission and stellar specific
intensity spectra (that is model-independent) from chemical and
physical interpretation.

---------------------------------------------------------
Title: Inside a VAMDC data node—putting standards into practical
software
Authors: Regandell, Samuel; Marquart, Thomas; Piskunov, Nikolai
2018PhyS...93c5001R Altcode: 2018arXiv180309217R
Access to molecular and atomic data is critical for many forms of remote
sensing analysis across different fields. Many atomic and molecular
databases are however highly specialised for their intended application,
complicating querying and combination data between sources. The Virtual
Atomic and Molecular Data Centre, VAMDC, is an electronic infrastructure
that allows each database to register as a ‘node’. Through services
such as VAMDC’s portal website, users can then access and query
all nodes in a homogenised way. Today all major Atomic and Molecular
databases are attached to VAMDC This article describes the software
tools we developed to help data providers create and manage a VAMDC
node. It gives an overview of the VAMDC infrastructure and of the
various standards it uses. The article then discusses the development
choices made and how the standards are implemented in practice. It
concludes with a full example of implementing a VAMDC node using a
real-life case as well as future plans for the node software.

---------------------------------------------------------
Title: Deriving stellar parameters with the SME software package
Authors: Piskunov, N.
2017sbcs.conf..209P Altcode:
Photometry and spectroscopy are complementary tools for deriving
accurate stellar parameters. Here I present one of the popular packages
for stellar spectroscopy called SME with the emphasis on the latest
developments and error assessment for the derived parameters.

---------------------------------------------------------
Title: Program Package for the Analysis of High Resolution High
Signal-To-Noise Stellar Spectra
Authors: Piskunov, N.; Ryabchikova, T.; Pakhomov, Yu.; Sitnova, T.;
Alekseeva, S.; Mashonkina, L.; Nordlander, T.
2017ASPC..510..509P Altcode: 2017arXiv171010856P
The program package SME (Spectroscopy Made Easy), designed to perform
an analysis of stellar spectra using spectral fitting techniques, was
updated due to adding new functions (isotopic and hyperfine splittins)
in VALD and including grids of NLTE calculations for energy levels
of few chemical elements. SME allows to derive automatically stellar
atmospheric parameters: effective temperature, surface gravity,
chemical abundances, radial and rotational velocities, turbulent
velocities, taking into account all the effects defining spectral line
formation. SME package uses the best grids of stellar atmospheres that
allows us to perform spectral analysis with the similar accuracy in
wide range of stellar parameters and metallicities - from dwarfs to
giants of BAFGK spectral classes.

---------------------------------------------------------
Title: VALD3: Current Developments
Authors: Pakhomov, Yu.; Piskunov, N.; Ryabchikova, T.
2017ASPC..510..518P Altcode: 2017arXiv171010854P
Today Vienna Atomic Line Database (VALD) is one of main databases
of atomic and molecular parameters required for stellar spectra
analysis. We present the new features that recently appeared in the
VALD3 release, including the effects of isotopic composition and
hyperfine splitting. The latest version of VALD contains parameters
for several isotopes of Li, Ca, Ti, Cu, Ba, Eu, and hyperfine splitting
of 35 isotopes from Li to Eu.

---------------------------------------------------------
Title: Main High-Resolution Near-IR Spectrometer for the VLT
Authors: Piskunov, N.
2017ASPC..510..514P Altcode:
We present the ongoing CRISES+ project on the development of a
cross-dispersed high resolution near-infrared spectrometer for the
ESO Very Large Telescope. The presentation highlights the relation
between science objectives, technical solutions, and the structure of
the project. We also share some of the insights on the implementation
and management of the project that are crucial for keeping the tight
time-line through efficient interaction between consortium members.

---------------------------------------------------------
Title: Erratum: Spectral Properties of Cool Stars:
Extended Abundance Analysis of 1617 Planet Search Stars (<A
href="https://doi.org/10.3847/0067-0049/225/2/32">2016, ApJS,
225, 32</A>)
Authors: Brewer, John M.; Fischer, Debra A.; Valenti, Jeff A.;
Piskunov, Nikolai
2017ApJS..230...12B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Spectroscopy Made Easy: Evolution
Authors: Piskunov, Nikolai; Valenti, Jeff A.
2017A&A...597A..16P Altcode: 2016arXiv160606073P; 2016A&A...597A..16P
Context. The Spectroscopy Made Easy (SME) package has become a popular
tool for analyzing stellar spectra, often in connection with large
surveys or exoplanet research. SME has evolved significantly since
it was first described in 1996, but many of the original caveats
and potholes still haunt users. The main drivers for this paper are
complexity of the modeling task, the large user community, and the
massive effort that has gone into SME. Aims: We do not intend
to give a comprehensive introduction to stellar atmospheres, but will
describe changes to key components of SME: the equation of state,
opacities, and radiative transfer. We will describe the analysis and
fitting procedure and investigate various error sources that affect
inferred parameters. Methods: We review the current status of
SME, emphasizing new algorithms and methods. We describe some best
practices for using the package, based on lessons learned over two
decades of SME usage. We present a new way to assess uncertainties
in derived stellar parameters. Results: Improvements made to
SME, better line data, and new model atmospheres yield more realistic
stellar spectra, but in many cases systematic errors still dominate
over measurement uncertainty. Future enhancements are outlined.

---------------------------------------------------------
Title: VizieR Online Data Catalog: Extended abundance analysis of
cool stars (Brewer+, 2016)
Authors: Brewer, J. M.; Fischer, D. A.; Valenti, J. A.; Piskunov, N.
2016yCat..22250032B Altcode:
The stellar spectra in this study were all collected using the
HIRES spectrograph (R~70000) on the Keck I telescope as part
of one or more radial-velocity planet-search programs under the
collaborative umbrella known as the California Planet Survey (CPS;
Howard+ 2010ApJ...721.1467H). In addition to stellar spectra,
our data also include 20 spectra of four different asteroids (4 Vesta,
1036 Ganymed, 3 Juno, and 10 Hygiea) from five epochs throughout
the 10-year period covered by the observations in our sample. These
spectra provided disk-integrated solar spectra and were obtained to
help calibrate our analysis by providing small zero-point offsets for
solar parameters and abundances. (4 data files).

---------------------------------------------------------
Title: Characterizing the cross dispersion reflection gratings
of CRIRES+
Authors: Follert, Roman; Taubert, Dieter; Hollandt, Jörg;
Monte, Christian; Oliva, Ernesto; Seemann, Ulf; Löwinger, Tom;
Anwand-Heerwart, Heiko; Schmidt, Christof; Dorn, Reinhold J.; Bristow,
Paul; Hatzes, Artie; Reiners, Ansgar; Piskunov, Nikolai; Heiter,
Ulrike; Stempels, Eric; Marquart, Thomas; Lavail, Alexis; Cumani,
Claudio; Grunhut, Jason; Haimerl, Andreas; Hinterschuster, Renate;
Ives, Derek J.; Jung, Yves; Kerber, Florian; Klein, Barbara; Lizon,
Jean Louis; Molina-Conde, Ignacio; Nicholson, Belinda; Origlia, Livia;
Pasquini, Luca; Paufique, Jérôme; Stegmeier, Jörg; Tordo, Sebastien
2016SPIE.9912E..2BF Altcode:
The CRIRES+ project attempts to upgrade the CRIRES instrument into a
cross dispersed Echelle spectrograph with a simultaneous recording of
8-10 diffraction orders. In order to transform the CRIRES spectrograph
into a cross-dispersing instrument, a set of six reflection gratings,
each one optimized for one of the wavelength bands CRIRES+ will
operate in (YJHKLM), will be used as cross dispersion elements
in CRIRES+. Due to the upgrade nature of the project, the choice
of gratings depends on the fixed geometry of the instrument. Thus,
custom made gratings would be required to achieve the ambitious design
goals. Custom made gratings have the disadvantage, though, that they
come at an extraordinary price and with lead times of more than 12
months. To mitigate this, a set of off-the-shelf gratings was obtained
which had grating parameters very close to the ones being identified
as optimal. To ensure that the rigorous specifications for CRIRES+
will be fulfilled, the CRIRES+ team started a collaboration with the
Physikalisch-Technische Bundesanstalt Berlin (PTB) to characterize
gratings underconditions similar to the operating conditions in CRIRES+
(angle of incidence, wavelength range). The respective test setup was
designed in collaboration between PTB and the CRIRES+ consortium. The
PTB provided optical radiation sources and calibrated detectors for
each wavelength range. With this setup, it is possible to measure the
absolute efficiency of the gratings both wavelength dependent and
polarization state dependent in a wavelength range from 0.9 μm to
6 μm.

---------------------------------------------------------
Title: VizieR Online Data Catalog: FGK dwarfs atmospheric parameters
(Ryabchikova+, 2016)
Authors: Ryabchikova, T.; Piskunov, N.; Pakhomov, Y.; Tsymbal, V.;
Titarenko, A.; Sitnova, T.; Alexeeva, S.; Fossati, L.; Mashonkina, L.
2016yCat..74561221R Altcode:
For the spectroscopic analysis, we choose the 13 MS stars including
the Sun (Table 1) in the 4900-6600K temperature range and with
metallicity between [Fe/H]=-1.5 and +0.3dex. All the stars, except HD
149026, have, at least, one interferometric determination of radius
and effective temperature. Spectra of the programme stars were
obtained with different spectrographs. Most data were extracted from
the following archives: the UVES/VLT and HARPS/3.6m spectrographs at
ESO,2 the ELODIE/1.93-m spectrograph3 at the Observatoire de Haute
Provence, and the ESPaDONs spectrograph at the Canada-France-Hawaii
Telescope (CFHT). Spectra of beta Vir and HD 103095 were obtained
with the FOCES spectrograph at 2.2-m telescope of the Calar Alto
Observatory. One of the spectra of 61 Vir was obtained with the Hamilton
Echelle Spectrograph attached to the Shane 3-m telescope of the Lick
Observatory. Spectra of few stars, including that of the Sun reflected
from Ganymede, were obtained with the HiReS/Keck spectrograph. (3
data files).

---------------------------------------------------------
Title: HARPS3 for a roboticized Isaac Newton Telescope
Authors: Thompson, Samantha J.; Queloz, Didier; Baraffe, Isabelle;
Brake, Martyn; Dolgopolov, Andrey; Fisher, Martin; Fleury, Michel;
Geelhoed, Joost; Hall, Richard; González Hernández, Jonay I.; ter
Horst, Rik; Kragt, Jan; Navarro, Ramón; Naylor, Tim; Pepe, Francesco;
Piskunov, Nikolai; Rebolo, Rafael; Sander, Louis; Ségransan, Damien;
Seneta, Eugene; Sing, David; Snellen, Ignas; Snik, Frans; Spronck,
Julien; Stempels, Eric; Sun, Xiaowei; Santana Tschudi, Samuel;
Young, John
2016SPIE.9908E..6FT Altcode: 2016arXiv160804611T
We present a description of a new instrument development, HARPS3,
planned to be installed on an upgraded and roboticized Isaac Newton
Telescope by end-2018. HARPS3 will be a high resolution (R≃115,000)
echelle spectrograph with a wavelength range from 380-690 nm. It is
being built as part of the Terra Hunting Experiment - a future 10-
year radial velocity measurement programme to discover Earth-like
exoplanets. The instrument design is based on the successful
HARPS spectrograph on the 3.6m ESO telescope and HARPS-N on the
TNG telescope. The main changes to the design in HARPS3 will be: a
customised fibre adapter at the Cassegrain focus providing a stabilised
beam feed and on-sky fibre diameter ≍1:4 arcsec, the implementation of
a new continuous ow cryostat to keep the CCD temperature very stable,
detailed characterisation of the HARPS3 CCD to map the effective pixel
positions and thus provide an improved accuracy wavelength solution,
an optimised integrated polarimeter and the instrument integrated into
a robotic operation. The robotic operation will optimise our programme
which requires our target stars to be measured on a nightly basis. We
present an overview of the entire project, including a description of
our anticipated robotic operation.

---------------------------------------------------------
Title: EELT-HIRES the high-resolution spectrograph for the E-ELT
Authors: Marconi, A.; Di Marcantonio, P.; D'Odorico, V.; Cristiani,
S.; Maiolino, R.; Oliva, E.; Origlia, L.; Riva, M.; Valenziano, L.;
Zerbi, F. M.; Abreu, M.; Adibekyan, V.; Allende Prieto, C.; Amado,
P. J.; Benz, W.; Boisse, I.; Bonfils, X.; Bouchy, F.; Buchhave,
L.; Buscher, D.; Cabral, A.; Canto Martins, B. L.; Chiavassa, A.;
Coelho, J.; Christensen, L. B.; Delgado-Mena, E.; de Medeiros, J. R.;
Di Varano, I.; Figueira, P.; Fisher, M.; Fynbo, J. P. U.; Glasse,
A. C. H.; Haehnelt, M.; Haniff, C.; Hansen, C. J.; Hatzes, A.; Huke,
P.; Korn, A. J.; Leão, I. C.; Liske, J.; Lovis, C.; Maslowski,
P.; Matute, I.; McCracken, R. A.; Martins, C. J. A. P.; Monteiro,
M. J. P. F. G.; Morris, S.; Morris, T.; Nicklas, H.; Niedzielski, A.;
Nunes, N. J.; Palle, E.; Parr-Burman, P. M.; Parro, V.; Parry, I.;
Pepe, F.; Piskunov, N.; Queloz, D.; Quirrenbach, A.; Rebolo Lopez,
R.; Reiners, A.; Reid, D. T.; Santos, N.; Seifert, W.; Sousa, S.;
Stempels, H. C.; Strassmeier, K.; Sun, X.; Udry, S.; Vanzi, L.;
Vestergaard, M.; Weber, M.; Zackrisson, E.
2016SPIE.9908E..23M Altcode: 2016arXiv160900497M
The first generation of E-ELT instruments will include an optic-infrared
High Resolution Spectrograph, conventionally indicated as EELT-HIRES,
which will be capable of providing unique breakthroughs in the fields
of exoplanets, star and planet formation, physics and evolution of
stars and galaxies, cosmology and fundamental physics. A 2-year long
phase A study for EELT-HIRES has just started and will be performed
by a consortium composed of institutes and organisations from Brazil,
Chile, Denmark, France, Germany, Italy, Poland, Portugal, Spain, Sweden,
Switzerland and United Kingdom. In this paper we describe the science
goals and the preliminary technical concept for EELT-HIRES which will
be developed during the phase A, as well as its planned development
and consortium organisation during the study.

---------------------------------------------------------
Title: 4MOST: the 4-metre Multi-Object Spectroscopic Telescope
project at preliminary design review
Authors: de Jong, Roelof S.; Barden, Samuel C.; Bellido-Tirado,
Olga; Brynnel, Joar G.; Frey, Steffen; Giannone, Domenico; Haynes,
Roger; Johl, Diana; Phillips, Daniel; Schnurr, Olivier; Walcher,
Jakob C.; Winkler, Roland; Ansorge, Wolfgang R.; Feltzing, Sofia;
McMahon, Richard G.; Baker, Gabriella; Caillier, Patrick; Dwelly,
Tom; Gaessler, Wolfgang; Iwert, Olaf; Mandel, Holger G.; Piskunov,
Nikolai A.; Pragt, Johan H.; Walton, Nicholas A.; Bensby, Thomas;
Bergemann, Maria; Chiappini, Cristina; Christlieb, Norbert; Cioni,
Maria-Rosa L.; Driver, Simon; Finoguenov, Alexis; Helmi, Amina; Irwin,
Michael J.; Kitaura, Francisco-Shu; Kneib, Jean-Paul; Liske, Jochen;
Merloni, Andrea; Minchev, Ivan; Richard, Johan; Starkenburg, Else
2016SPIE.9908E..1OD Altcode:
We present an overview of the 4MOST project at the Preliminary Design
Review. 4MOST is a major new wide-field, high-multiplex spectroscopic
survey facility under development for the VISTA telescope of ESO. 4MOST
has a broad range of science goals ranging from Galactic Archaeology
and stellar physics to the high-energy physics, galaxy evolution,
and cosmology. Starting in 2021, 4MOST will deploy 2436 fibres in
a 4.1 square degree field-of-view using a positioner based on the
tilting spine principle. The fibres will feed one high-resolution (R
20,000) and two medium resolution (R 5000) spectrographs with fixed
3-channel designs and identical 6k x 6k CCD detectors. 4MOST will have
a unique operations concept in which 5-year public surveys from both
the consortium and the ESO community will be combined and observed in
parallel during each exposure. The 4MOST Facility Simulator (4FS) was
developed to demonstrate the feasibility of this observing concept,
showing that we can expect to observe more than 25 million objects
in each 5-year survey period and will eventually be used to plan and
conduct the actual survey.

---------------------------------------------------------
Title: Spectral Properties of Cool Stars: Extended Abundance Analysis
of 1,617 Planet-search Stars
Authors: Brewer, John M.; Fischer, Debra A.; Valenti, Jeff A.;
Piskunov, Nikolai
2016ApJS..225...32B Altcode: 2016arXiv160607929B
We present a catalog of uniformly determined stellar properties and
abundances for 1,617 F, G, and K stars using an automated spectral
synthesis modeling procedure. All stars were observed using the HIRES
spectrograph at Keck Observatory. Our procedure used a single line
list to fit model spectra to observations of all stars to determine
effective temperature, surface gravity, metallicity, projected
rotational velocity, and the abundances of 15 elements (C, N, O,
Na, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Ni, and Y). Sixty percent
of the sample had Hipparcos parallaxes and V-band photometry, which
we combined with the spectroscopic results to obtain mass, radius,
and luminosity. Additionally, we used the luminosity, effective
temperature, metallicity and α-element enhancement to interpolate in
the Yonsei-Yale isochrones to derive mass, radius, gravity, and age
ranges for those stars. Finally, we determined new relations between
effective temperature and macroturbulence for dwarfs and subgiants. Our
analysis achieved precisions of 25 K in {T}{eff}, 0.01 dex in
[M/H], 0.028 dex for {log}g, and 0.5 km s-1 in v\sin I based
on multiple observations of the same stars. The abundance results were
similarly precise, between ∼0.01 and ∼0.04 dex, though trends with
respect to {T}{eff} remained for which we derived empirical
corrections. The trends, though small, were much larger than our
uncertainties and are shared with published abundances. We show that
changing our model atmosphere grid accounts for most of the trend in
[M/H] between 5000 and 5500 K, indicating a possible problem with the
atmosphere models or opacities.

---------------------------------------------------------
Title: The "+" for CRIRES: enabling better science at infrared
wavelength and high spectral resolution at the ESO VLT
Authors: Dorn, Reinhold J.; Follert, Roman; Bristow, Paul; Cumani,
Claudio; Eschbaumer, Siegfried; Grunhut, Jason; Haimerl, Andreas;
Hatzes, Artie; Heiter, Ulrike; Hinterschuster, Renate; Ives, Derek
J.; Jung, Yves; Kerber, Florian; Klein, Barbara; Lavail, Alexis;
Lizon, Jean Louis; Löwinger, Tom; Molina-Conde, Ignacio; Nicholson,
Belinda; Marquart, Thomas; Oliva, Ernesto; Origlia, Livia; Pasquini,
Luca; Paufique, Jérôme; Piskunov, Nikolai; Reiners, Ansgar; Seemann,
Ulf; Stegmeier, Jörg; Stempels, Eric; Tordo, Sebastien
2016SPIE.9908E..0ID Altcode:
The adaptive optics (AO) assisted CRIRES instrument is an IR (0.92
- 5.2 μm) high-resolution spectrograph was in operation from 2006
to 2014 at the Very Large Telescope (VLT) observatory. CRIRES was
a unique instrument, accessing a parameter space (wavelength range
and spectral resolution) up to now largely uncharted. It consisted
of a single-order spectrograph providing long-slit (40 arcsecond)
spectroscopy with a resolving power up to R=100 000. However the
setup was limited to a narrow, single-shot, spectral range of
about 1/70 of the central wavelength, resulting in low observing
efficiency for many scientific programmes requiring a broad spectral
coverage. The CRIRES upgrade project, CRIRES+, transforms
this VLT instrument into a cross-dispersed spectrograph to increase the
simultaneously covered wavelength range by a factor of ten. A new and
larger detector focal plane array of three Hawaii 2RG detectors with
5.3 μm cut-off wavelength will replace the existing detectors. For
advanced wavelength calibration, custom-made absorption gas cells and
an etalon system will be added. A spectro-polarimetric unit will allow
the recording of circular and linear polarized spectra. This upgrade
will be supported by dedicated data reduction software allowing the
community to take full advantage of the new capabilities offered by
CRIRES+. CRIRES+ has now entered its assembly
and integration phase and will return with all new capabilities by the
beginning of 2018 to the Very Large Telescope in Chile. This article
will provide the reader with an update of the current status of the
instrument as well as the remaining steps until final installation at
the Paranal Observatory.

---------------------------------------------------------
Title: CRIRES+: A High Resolution Near-Infrared Spectro(Polari)Meter
At The VLT
Authors: Lavail, Alexis; Piskunov, Nikolai; Heiter, Ulrike; Marquart,
Thomas; Stempels, Eric; Crires+ Consortium
2016csss.confE..48L Altcode:
CRIRES, the CRyogenic high-resolution InfraRed Echelle Spectrograph
has been removed from the ESO's Very Large Telescope in 2014 to
undergo a massive upgrade. The upgraded CRIRES+ instrument will
be a cross-dispersed spectrograph; gain a tenfold increase in
simultaneous wavelength coverage; have new detectors, gas cells for
wavelength calibration, polarimeter unit enabling spectropolarimeteric
observations; and benefit from a new Data Reduction Software.

---------------------------------------------------------
Title: Hunting For Strong Magnetic Fields In Rapidly Rotating Sun-Like
Stars With Stokes-I Observations
Authors: Shulyak, Denis; Malo, Lison; Reiners, Ansgar; Kochukhov,
Oleg; Jeffers, Sandra; Piskunov, Nikolai
2016csss.confE.118S Altcode:
Stars with convective envelopes can generate strong magnetic fields through rotationally driven dynamos. Theory suggests that the
maximum magnetic field strength depends on the energy budget
stored in the stellar convective shell and can reach values
of several kilogauss in fastest rotating stars. We test this
predictions by measuring total magnetic flux and polarization
in a sample of sun-like stars that rotate close to the activity
saturation limit. We detect average magnetic flux densities of
several hundred G in several of our targets,with the strongest field
of about 1 kG in a K type star V383 Lac showing that young sun-like
starscan produce average fields on the kG level.

---------------------------------------------------------
Title: Hlinop: April 2016 Release
Authors: Barklem, Paul; Piskunov, Nikolai
2016zndo.....50215B Altcode:
First formal github release. April 2016 version.

---------------------------------------------------------
Title: Highlights of IAU Commission 29: Recent Advances and
Perspectives on Stellar Spectroscopy
Authors: Cunha, Katia; Soderblom, David R.; Piskunov, Nikolai; Aoki,
Wako; Asplund, Martin; Carpenter, Kenneth G.; Crowther, Paul; Melendez,
Jorge; Venn, Kimberly; Hill, Vanessa; Yong, David
2016IAUTA..29..428C Altcode:
IAU Commission 29 - Stellar Spectra has been one of the IAU commissions
from the onset, until its dissolution at the most recent IAU General
Assembly in Honolulu in 2015. This commission belonged to IAU Division
G (“Stars and Stellar Physics”), the latter committed with fostering
research in stellar astrophysics. Within the general field of stellar
astrophysics, stellar spectroscopy plays a key role, as stellar
spectra are a powerful tool providing a view into the detailed physical
properties of stars and the physical processes occuring within them.

---------------------------------------------------------
Title: Accuracy of atmospheric parameters of FGK dwarfs determined
by spectrum fitting
Authors: Ryabchikova, T.; Piskunov, N.; Pakhomov, Yu.; Tsymbal, V.;
Titarenko, A.; Sitnova, T.; Alexeeva, S.; Fossati, L.; Mashonkina, L.
2016MNRAS.456.1221R Altcode: 2015arXiv151106134R
We performed extensive tests of the accuracy of atmospheric parameter
determination for FGK stars based on the spectrum fitting procedure
Spectroscopy Made Easy (SME). Our stellar sample consists of 13
objects, including the Sun, in the temperature range 5000-6600 K and
metallicity range -1.4-+0.4. The analysed stars have the advantage
of having parameters derived by interferometry. For each star, we
use spectra obtained with different spectrographs and different
signal-to-noise ratios (S/N). For the fitting, we adopted three
different sets of constraints and test how the derived parameters
depend upon the spectral regions (masks) used in SME. We developed and
implemented in SME a new method for estimating uncertainties in the
resulting parameters based on fitting residuals, partial derivatives,
and data uncertainties. For stars in the 5700-6600 K range, the best
agreement with the effective temperatures derived by interferometry
is achieved when spectrum fitting includes the H α and H β lines,
while for cooler stars the choice of the mask does not affect the
results. The derived atmospheric parameters do not strongly depend on
spectral resolution and S/N of the observations, while the uncertainties
in temperature and surface gravity increase with increasing effective
temperature, with minima at 50 K in Teff and 0.1 dex in log
g, for spectra with S/N=150-200. A non-local thermodynamic equilibrium
(NLTE) analysis of the Ti I/Ti II and Fe I/Fe II ionization equilibria
and abundances determined from the atomic C I (NLTE) and molecular
CH species supports the parameters we derived with SME by fitting the
observed spectra including the hydrogen lines.

---------------------------------------------------------
Title: Scientific problems addressed by the Spektr-UV space project
(world space Observatory—Ultraviolet)
Authors: Boyarchuk, A. A.; Shustov, B. M.; Savanov, I. S.; Sachkov,
M. E.; Bisikalo, D. V.; Mashonkina, L. I.; Wiebe, D. Z.; Shematovich,
V. I.; Shchekinov, Yu. A.; Ryabchikova, T. A.; Chugai, N. N.; Ivanov,
P. B.; Voshchinnikov, N. V.; Gomez de Castro, A. I.; Lamzin, S. A.;
Piskunov, N.; Ayres, T.; Strassmeier, K. G.; Jeffrey, S.; Zwintz,
S. K.; Shulyak, D.; Gérard, J. -C.; Hubert, B.; Fossati, L.; Lammer,
H.; Werner, K.; Zhilkin, A. G.; Kaigorodov, P. V.; Sichevskii, S. G.;
Ustamuich, S.; Kanev, E. N.; Kil'pio, E. Yu.
2016ARep...60....1B Altcode:
The article presents a review of scientific problems and methods of
ultraviolet astronomy, focusing on perspective scientific problems
(directions) whose solution requires UV space observatories. These
include reionization and the history of star formation in the Universe,
searches for dark baryonic matter, physical and chemical processes
in the interstellar medium and protoplanetary disks, the physics of
accretion and outflows in astrophysical objects, from Active Galactic
Nuclei to close binary stars, stellar activity (for both low-mass and
high-mass stars), and processes occurring in the atmospheres of both
planets in the solar system and exoplanets. Technological progress
in UV astronomy achieved in recent years is also considered. The
well advanced, international, Russian-led Spektr-UV (World Space
Observatory—Ultraviolet) project is described in more detail. This
project is directed at creating a major space observatory operational
in the ultraviolet (115-310 nm). This observatory will provide an
effective, and possibly the only, powerful means of observing in this
spectral range over the next ten years, and will be an powerful tool
for resolving many topical scientific problems.

---------------------------------------------------------
Title: The EChO science case
Authors: Tinetti, Giovanna; Drossart, Pierre; Eccleston, Paul; Hartogh,
Paul; Isaak, Kate; Linder, Martin; Lovis, Christophe; Micela, Giusi;
Ollivier, Marc; Puig, Ludovic; Ribas, Ignasi; Snellen, Ignas; Swinyard,
Bruce; Allard, France; Barstow, Joanna; Cho, James; Coustenis, Athena;
Cockell, Charles; Correia, Alexandre; Decin, Leen; de Kok, Remco;
Deroo, Pieter; Encrenaz, Therese; Forget, Francois; Glasse, Alistair;
Griffith, Caitlin; Guillot, Tristan; Koskinen, Tommi; Lammer, Helmut;
Leconte, Jeremy; Maxted, Pierre; Mueller-Wodarg, Ingo; Nelson, Richard;
North, Chris; Pallé, Enric; Pagano, Isabella; Piccioni, Guseppe;
Pinfield, David; Selsis, Franck; Sozzetti, Alessandro; Stixrude,
Lars; Tennyson, Jonathan; Turrini, Diego; Zapatero-Osorio, Mariarosa;
Beaulieu, Jean-Philippe; Grodent, Denis; Guedel, Manuel; Luz, David;
Nørgaard-Nielsen, Hans Ulrik; Ray, Tom; Rickman, Hans; Selig,
Avri; Swain, Mark; Banaszkiewicz, Marek; Barlow, Mike; Bowles, Neil;
Branduardi-Raymont, Graziella; du Foresto, Vincent Coudé; Gerard,
Jean-Claude; Gizon, Laurent; Hornstrup, Allan; Jarchow, Christopher;
Kerschbaum, Franz; Kovacs, Géza; Lagage, Pierre-Olivier; Lim, Tanya;
Lopez-Morales, Mercedes; Malaguti, Giuseppe; Pace, Emanuele; Pascale,
Enzo; Vandenbussche, Bart; Wright, Gillian; Ramos Zapata, Gonzalo;
Adriani, Alberto; Azzollini, Ruymán; Balado, Ana; Bryson, Ian;
Burston, Raymond; Colomé, Josep; Crook, Martin; Di Giorgio, Anna;
Griffin, Matt; Hoogeveen, Ruud; Ottensamer, Roland; Irshad, Ranah;
Middleton, Kevin; Morgante, Gianluca; Pinsard, Frederic; Rataj, Mirek;
Reess, Jean-Michel; Savini, Giorgio; Schrader, Jan-Rutger; Stamper,
Richard; Winter, Berend; Abe, L.; Abreu, M.; Achilleos, N.; Ade, P.;
Adybekian, V.; Affer, L.; Agnor, C.; Agundez, M.; Alard, C.; Alcala,
J.; Allende Prieto, C.; Alonso Floriano, F. J.; Altieri, F.; Alvarez
Iglesias, C. A.; Amado, P.; Andersen, A.; Aylward, A.; Baffa, C.;
Bakos, G.; Ballerini, P.; Banaszkiewicz, M.; Barber, R. J.; Barrado,
D.; Barton, E. J.; Batista, V.; Bellucci, G.; Belmonte Avilés,
J. A.; Berry, D.; Bézard, B.; Biondi, D.; Błęcka, M.; Boisse, I.;
Bonfond, B.; Bordé, P.; Börner, P.; Bouy, H.; Brown, L.; Buchhave,
L.; Budaj, J.; Bulgarelli, A.; Burleigh, M.; Cabral, A.; Capria,
M. T.; Cassan, A.; Cavarroc, C.; Cecchi-Pestellini, C.; Cerulli,
R.; Chadney, J.; Chamberlain, S.; Charnoz, S.; Christian Jessen,
N.; Ciaravella, A.; Claret, A.; Claudi, R.; Coates, A.; Cole, R.;
Collura, A.; Cordier, D.; Covino, E.; Danielski, C.; Damasso, M.;
Deeg, H. J.; Delgado-Mena, E.; Del Vecchio, C.; Demangeon, O.; De Sio,
A.; De Wit, J.; Dobrijévic, M.; Doel, P.; Dominic, C.; Dorfi, E.;
Eales, S.; Eiroa, C.; Espinoza Contreras, M.; Esposito, M.; Eymet,
V.; Fabrizio, N.; Fernández, M.; Femenía Castella, B.; Figueira,
P.; Filacchione, G.; Fletcher, L.; Focardi, M.; Fossey, S.; Fouqué,
P.; Frith, J.; Galand, M.; Gambicorti, L.; Gaulme, P.; García López,
R. J.; Garcia-Piquer, A.; Gear, W.; Gerard, J. -C.; Gesa, L.; Giani,
E.; Gianotti, F.; Gillon, M.; Giro, E.; Giuranna, M.; Gomez, H.;
Gomez-Leal, I.; Gonzalez Hernandez, J.; González Merino, B.; Graczyk,
R.; Grassi, D.; Guardia, J.; Guio, P.; Gustin, J.; Hargrave, P.; Haigh,
J.; Hébrard, E.; Heiter, U.; Heredero, R. L.; Herrero, E.; Hersant,
F.; Heyrovsky, D.; Hollis, M.; Hubert, B.; Hueso, R.; Israelian, G.;
Iro, N.; Irwin, P.; Jacquemoud, S.; Jones, G.; Jones, H.; Justtanont,
K.; Kehoe, T.; Kerschbaum, F.; Kerins, E.; Kervella, P.; Kipping, D.;
Koskinen, T.; Krupp, N.; Lahav, O.; Laken, B.; Lanza, N.; Lellouch,
E.; Leto, G.; Licandro Goldaracena, J.; Lithgow-Bertelloni, C.; Liu,
S. J.; Lo Cicero, U.; Lodieu, N.; Lognonné, P.; Lopez-Puertas,
M.; Lopez-Valverde, M. A.; Lundgaard Rasmussen, I.; Luntzer, A.;
Machado, P.; MacTavish, C.; Maggio, A.; Maillard, J. -P.; Magnes, W.;
Maldonado, J.; Mall, U.; Marquette, J. -B.; Mauskopf, P.; Massi, F.;
Maurin, A. -S.; Medvedev, A.; Michaut, C.; Miles-Paez, P.; Montalto,
M.; Montañés Rodríguez, P.; Monteiro, M.; Montes, D.; Morais, H.;
Morales, J. C.; Morales-Calderón, M.; Morello, G.; Moro Martín,
A.; Moses, J.; Moya Bedon, A.; Murgas Alcaino, F.; Oliva, E.; Orton,
G.; Palla, F.; Pancrazzi, M.; Pantin, E.; Parmentier, V.; Parviainen,
H.; Peña Ramírez, K. Y.; Peralta, J.; Perez-Hoyos, S.; Petrov, R.;
Pezzuto, S.; Pietrzak, R.; Pilat-Lohinger, E.; Piskunov, N.; Prinja,
R.; Prisinzano, L.; Polichtchouk, I.; Poretti, E.; Radioti, A.; Ramos,
A. A.; Rank-Lüftinger, T.; Read, P.; Readorn, K.; Rebolo López,
R.; Rebordão, J.; Rengel, M.; Rezac, L.; Rocchetto, M.; Rodler, F.;
Sánchez Béjar, V. J.; Sanchez Lavega, A.; Sanromá, E.; Santos,
N.; Sanz Forcada, J.; Scandariato, G.; Schmider, F. -X.; Scholz,
A.; Scuderi, S.; Sethenadh, J.; Shore, S.; Showman, A.; Sicardy, B.;
Sitek, P.; Smith, A.; Soret, L.; Sousa, S.; Stiepen, A.; Stolarski,
M.; Strazzulla, G.; Tabernero, H. M.; Tanga, P.; Tecsa, M.; Temple,
J.; Terenzi, L.; Tessenyi, M.; Testi, L.; Thompson, S.; Thrastarson,
H.; Tingley, B. W.; Trifoglio, M.; Martín Torres, J.; Tozzi, A.;
Turrini, D.; Varley, R.; Vakili, F.; de Val-Borro, M.; Valdivieso,
M. L.; Venot, O.; Villaver, E.; Vinatier, S.; Viti, S.; Waldmann,
I.; Waltham, D.; Ward-Thompson, D.; Waters, R.; Watkins, C.; Watson,
D.; Wawer, P.; Wawrzaszk, A.; White, G.; Widemann, T.; Winek, W.;
Wiśniowski, T.; Yelle, R.; Yung, Y.; Yurchenko, S. N.
2015ExA....40..329T Altcode: 2015ExA...tmp...67T; 2015arXiv150205747T
The discovery of almost two thousand exoplanets has revealed an
unexpectedly diverse planet population. We see gas giants in few-day
orbits, whole multi-planet systems within the orbit of Mercury,
and new populations of planets with masses between that of the Earth
and Neptune—all unknown in the Solar System. Observations to date
have shown that our Solar System is certainly not representative of
the general population of planets in our Milky Way. The key science
questions that urgently need addressing are therefore: What are
exoplanets made of? Why are planets as they are? How do planetary
systems work and what causes the exceptional diversity observed as
compared to the Solar System? The EChO (Exoplanet Characterisation
Observatory) space mission was conceived to take up the challenge to
explain this diversity in terms of formation, evolution, internal
structure and planet and atmospheric composition. This requires
in-depth spectroscopic knowledge of the atmospheres of a large and
well-defined planet sample for which precise physical, chemical and
dynamical information can be obtained. In order to fulfil this ambitious
scientific program, EChO was designed as a dedicated survey mission
for transit and eclipse spectroscopy capable of observing a large,
diverse and well-defined planet sample within its 4-year mission
lifetime. The transit and eclipse spectroscopy method, whereby the
signal from the star and planet are differentiated using knowledge of
the planetary ephemerides, allows us to measure atmospheric signals
from the planet at levels of at least 10-4 relative to
the star. This can only be achieved in conjunction with a carefully
designed stable payload and satellite platform. It is also necessary
to provide broad instantaneous wavelength coverage to detect as many
molecular species as possible, to probe the thermal structure of the
planetary atmospheres and to correct for the contaminating effects of
the stellar photosphere. This requires wavelength coverage of at least
0.55 to 11 μm with a goal of covering from 0.4 to 16 μm. Only modest
spectral resolving power is needed, with R ~ 300 for wavelengths less
than 5 μm and R ~ 30 for wavelengths greater than this. The transit
spectroscopy technique means that no spatial resolution is required. A
telescope collecting area of about 1 m2 is sufficiently
large to achieve the necessary spectro-photometric precision: for the
Phase A study a 1.13 m2 telescope, diffraction limited at 3
μm has been adopted. Placing the satellite at L2 provides a cold and
stable thermal environment as well as a large field of regard to allow
efficient time-critical observation of targets randomly distributed over
the sky. EChO has been conceived to achieve a single goal: exoplanet
spectroscopy. The spectral coverage and signal-to-noise to be achieved
by EChO, thanks to its high stability and dedicated design, would be
a game changer by allowing atmospheric composition to be measured
with unparalleled exactness: at least a factor 10 more precise and
a factor 10 to 1000 more accurate than current observations. This
would enable the detection of molecular abundances three orders of
magnitude lower than currently possible and a fourfold increase from
the handful of molecules detected to date. Combining these data with
estimates of planetary bulk compositions from accurate measurements
of their radii and masses would allow degeneracies associated with
planetary interior modelling to be broken, giving unique insight
into the interior structure and elemental abundances of these alien
worlds. EChO would allow scientists to study exoplanets both as a
population and as individuals. The mission can target super-Earths,
Neptune-like, and Jupiter-like planets, in the very hot to temperate
zones (planet temperatures of 300-3000 K) of F to M-type host stars. The
EChO core science would be delivered by a three-tier survey. The EChO
Chemical Census: This is a broad survey of a few-hundred exoplanets,
which allows us to explore the spectroscopic and chemical diversity of
the exoplanet population as a whole. The EChO Origin: This is a deep
survey of a subsample of tens of exoplanets for which significantly
higher signal to noise and spectral resolution spectra can be obtained
to explain the origin of the exoplanet diversity (such as formation
mechanisms, chemical processes, atmospheric escape). The EChO Rosetta
Stones: This is an ultra-high accuracy survey targeting a subsample
of select exoplanets. These will be the bright "benchmark" cases
for which a large number of measurements would be taken to explore
temporal variations, and to obtain two and three dimensional spatial
information on the atmospheric conditions through eclipse-mapping
techniques. If EChO were launched today, the exoplanets currently
observed are sufficient to provide a large and diverse sample. The
Chemical Census survey would consist of &gt; 160 exoplanets with a range
of planetary sizes, temperatures, orbital parameters and stellar host
properties. Additionally, over the next 10 years, several new ground-
and space-based transit photometric surveys and missions will come
on-line (e.g. NGTS, CHEOPS, TESS, PLATO), which will specifically focus
on finding bright, nearby systems. The current rapid rate of discovery
would allow the target list to be further optimised in the years prior
to EChO's launch and enable the atmospheric characterisation of hundreds
of planets.

---------------------------------------------------------
Title: Doppler imaging of LQ Hydrae for 1998-2002
Authors: Cole, E. M.; Hackman, T.; Käpylä, M. J.; Ilyin, I.;
Kochukhov, O.; Piskunov, N.
2015A&A...581A..69C Altcode: 2015arXiv150403673C
 Aims: We study the spot distribution on the surface of LQ Hya
during the observing seasons October 1998-November 2002. We look for
persistent active longitudes, trends in the level of spot activity
and compare to photometric data. Methods: We apply the Doppler
imaging technique on photospheric spectral lines using an inversion
code to retrieve images of the surface temperature. Results:
We present new temperature maps using multiple spectral lines for
a total of 7 seasons. Conclusions: We find no evidence for
active longitudes persisting over multiple observing seasons. The spot
activity appears to be concentrated to two latitude regions. Using
the currently accepted rotation period, we find spot structures
to show a trend in the phase-time plot, indicative of a need for
a longer period. We conclude that the long-term activity of LQ Hya
is more chaotic than that of some magnetically active binary stars
analyzed with similar methods, but still with clear indications of
an activity cycle from the photometry. Based on observations
made with the Nordic Optical Telescope, operated on the island of La
Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the
Spanish Observatorio del Roque de los Muchachos of the Instituto de
Astrofisica de Canarias. Table 2 is available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201425440/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: Using near-infrared spectroscopy for characterization of
transiting exoplanets (Corrigendum)
Authors: Aronson, E.; Waldén, P.; Piskunov, N.
2015A&A...581C...1A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: HLINOP: Hydrogen LINe OPacity in stellar atmospheres
Authors: Barklem, P. S.; Piskunov, N.
2015ascl.soft07008B Altcode:
HLINOP is a collection of codes for computing hydrogen line profiles
and opacities in the conditions typical of stellar atmospheres. It
includes HLINOP for approximate quick calculation of any line of
neutral hydrogen (suitable for model atmosphere calculations),
based on the Fortran code of Kurucz and Peterson found in <A
href="http://kurucz.harvard.edu/programs/atlas9/atlas9xlinop.for">ATLAS9</A>.
It also includes HLINPROF, for detailed, accurate calculation of lower
Balmer line profiles (suitable for detailed analysis of Balmer lines)
and HBOP, to implement the occupation probability formalism of Daeppen,
Anderson and Milhalas (1987) and thus account for the merging of
bound-bound and bound-free opacity (used often as a wrapper to HLINOP
for model atmosphere calculations).

---------------------------------------------------------
Title: Posters: Poster #73927: High-resolution transmission
spectroscopy of exoplanets with the ground-based instruments
Authors: Piskunov, Nikolai; Aronson, Erik
2015pthp.confE..54P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Accurate Gravities of F, G, and K stars from High Resolution
Spectra Without External Constraints
Authors: Brewer, John M.; Fischer, Debra A.; Basu, Sarbani; Valenti,
Jeff A.; Piskunov, Nikolai
2015ApJ...805..126B Altcode: 2015arXiv150307180B
We demonstrate a new procedure to derive accurate and precise surface
gravities from high resolution spectra without the use of external
constraints. Our analysis utilizes Spectroscopy Made Easy with robust
spectral line constraints and uses an iterative process to mitigate
degeneracies in the fitting process. We adopt an updated radiative
transfer code, a new treatment for neutral perturber broadening, a line
list with multiple gravity constraints and separate fitting for global
stellar properties and abundance determinations. To investigate the
sources of temperature dependent trends in determining log {\mkern 1mu}
g noted in previous studies, we obtained Keck HIRES spectra of 42 Kepler
asteroseismic stars. In comparison to asteroseismically determined log
{\mkern 1mu} g our spectroscopic analysis has a constant offset of 0.01
dex with a rms scatter of 0.05 dex. We also analyzed 30 spectra which
had published surface gravities determined using the a/{{R}*}
technique from planetary transits and found a constant offset of 0.06
dex and rms scatter of 0.07 dex. The two samples covered effective
temperatures between 5000 and 6700 K with log {\mkern 1mu} g between
3.7 and 4.6.

---------------------------------------------------------
Title: On the Accuracy of Atmospheric Parameter Determination in
BAFGK Stars
Authors: Ryabchikova, T.; Piskunov, N.; Shulyak, D.
2015ASPC..494..308R Altcode:
During the past few years, many papers determining the atmospheric
parameters in FGK stars appeared in the literature where the accuracy
of effective temperatures is given as 20-40 K. For main sequence
stars within the 5 000-13 000 K temperature range, we have performed
a comparative analysis of the parameters derived from the spectra by
using the SME (Spectroscopy Made Easy) package and those found in the
literature. Our sample includes standard stars Sirius, Procyon, δ
Eri, and the Sun. Combining different spectral regions in the fitting
procedure, we investigated an effect different atomic species have
on the derived atmospheric parameters. The temperature difference
may exceed 100 K depending on the spectral regions used in the SME
procedure. It is shown that the atmospheric parameters derived with
the SME procedure which includes wings of hydrogen lines in fitting
agrees better with the results derived by the other methods and tools
across a large part of the main sequence. For three stars—π Cet,
21 Peg, and Procyon—the atmospheric parameters were also derived by
fitting a calculated energy distribution to the observed one. We found
a substantial difference in the parameters inferred from different sets
and combinations of spectrophotometric observations. An intercomparison
of our results and literature data shows that the average accuracy of
effective temperature determination for cool stars and for the early
B-stars is 70-85 K and 170-200 K, respectively.

---------------------------------------------------------
Title: Stellar activity as noise in exoplanet detection - I. Methods
and application to solar-like stars and activity cycles
Authors: Korhonen, H.; Andersen, J. M.; Piskunov, N.; Hackman, T.;
Juncher, D.; Järvinen, S. P.; Jørgensen, U. G.
2015MNRAS.448.3038K Altcode: 2015arXiv150100981K
The detection of exoplanets using any method is prone to confusion
due to the intrinsic variability of the host star. We investigate the
effect of cool starspots on the detectability of the exoplanets around
solar-like stars using the radial velocity method. For investigating
this activity-caused `jitter' we calculate synthetic spectra using
radiative transfer, known stellar atomic and molecular lines, different
surface spot configurations and an added planetary signal. Here, the
methods are described in detail, tested and compared to previously
published studies. The methods are also applied to investigate the
activity jitter in old and young solar-like stars, and over a solar-like
activity cycles. We find that the mean full jitter amplitude obtained
from the spot surfaces mimicking the solar activity varies during the
cycle approximately between 1 and 9 m s-1. With a realistic
observing frequency a Neptune-mass planet on a 1-yr orbit can be
reliably recovered. On the other hand, the recovery of an Earth-mass
planet on a similar orbit is not feasible with high significance. The
methods developed in this study have a great potential for doing
statistical studies of planet detectability, and also for investigating
the effect of stellar activity on recovered planetary parameters.

---------------------------------------------------------
Title: Magnetic field topology and chemical spot distributions in
the extreme Ap star HD 75049
Authors: Kochukhov, O.; Rusomarov, N.; Valenti, J. A.; Stempels, H. C.;
Snik, F.; Rodenhuis, M.; Piskunov, N.; Makaganiuk, V.; Keller, C. U.;
Johns-Krull, C. M.
2015A&A...574A..79K Altcode: 2014arXiv1411.7518K
Context. Intermediate-mass, magnetic chemically peculiar (Ap) stars
provide a unique opportunity to study the topology of stellar magnetic
fields in detail and to investigate magnetically driven processes
of spot formation. Aims: Here we aim to derive the surface
magnetic field geometry and chemical abundance distributions for the
extraordinary Ap star HD 75049. This object hosts a surface field of
~30 kG, one of the strongest known for any non-degenerate star. 
Methods: We used time-series of high-resolution HARPS intensity and
circular polarisation observations. These data were interpreted with the
help of magnetic Doppler imaging and model atmospheres incorporating
effects of a non-solar chemical composition and a strong magnetic
field. Results: Based on high-precision measurements of the
mean magnetic field modulus, we refined the rotational period of HD
75049 to Prot = 4.048267 ± 0.000036 d. We also derived
basic stellar parameters, Teff = 10 250 ± 250 K and log g =
4.3 ± 0.1. Magnetic Doppler imaging revealed that the field topology
of HD 75049 is poloidal and dominated by a dipolar contribution with
a peak surface field strength of 39 kG. At the same time, deviations
from the classical axisymmetric oblique dipolar configuration are
significant. Chemical surface maps of Si, Cr, Fe, and Nd show abundance
contrasts of 0.5-1.4 dex, which is low compared with many other Ap
stars. Of the chemical elements, Nd is found to be enhanced close to
the magnetic pole, whereas Si and Cr are concentrated predominantly
at the magnetic equator. The iron distribution shows low-contrast
features both at the magnetic equator and the pole. Conclusions:
The morphology of the magnetic field and the properties of chemical
spots in HD 75049 are qualitatively similar to those of Ap stars with
weaker fields. Consequently, whatever mechanism forms and sustains
global magnetic fields in intermediate-mass main-sequence stars, it
operates in the same way over the entire observed range of magnetic
field strengths. Based on observations collected at the European
Southern Observatory, Chile (ESO programs 084.D-0338, 085.D-0296,
086.D-0240, 088.D-0066, 090.D-0256, 078.D-0192, 080.D-0170).

---------------------------------------------------------
Title: Serendipitous Discovery of a Dwarf Nova in the Kepler Field
Near the G Dwarf KIC 5438845
Authors: Brown, Alexander; Neff, James E.; Ayres, Thomas R.; Kowalski,
Adam; Hawley, Suzanne; Berdyugina, Svetlana; Harper, Graham M.;
Korhonen, Heidi; Piskunov, Nikolai; Saar, Steven; Walkowicz, Lucianne;
Wells, Mark A.
2015AJ....149...67B Altcode:
The Kepler satellite provides a unique window into stellar temporal
variability by observing a wide variety of stars with multi-year,
near-continuous, high precision, optical photometric time series. While
most Kepler targets are faint stars with poorly known physical
properties, many unexpected discoveries should result from a long
photometric survey of such a large area of sky. During our Kepler
Guest Observer programs that monitored late-type stars for starspot and
flaring variability, we discovered a previously unknown dwarf nova that
lies within a few arcseconds of the mid-G dwarf star KIC 5438845. This
dwarf nova underwent nine outbursts over a 4 year time span. The two
largest outbursts lasted ∼17-18 days and show strong modulations with
a 110.8 minute period and a declining amplitude during the outburst
decay phase. These properties are characteristic of an SU UMa-type
cataclysmic variable. By analogy with other dwarf nova light curves,
we associate the 110.8 minute (1.847 hr) period with the superhump
period, close to but slightly longer than the orbital period of the
binary. No precursor outbursts are seen before the super-outbursts
and the overall super-outburst morphology corresponds to Osaki &amp;
Meyer “Case B” outbursts, which are initiated when the outer edge
of the disk reaches the tidal truncation radius. “Case B” outbursts
are rare within the Kepler light curves of dwarf novae. The dwarf nova
is undergoing relatively slow mass transfer, as evidenced by the long
intervals between outbursts, but the mass transfer rate appears to
be steady, because the smaller “normal” outbursts show a strong
correlation between the integrated outburst energy and the elapsed time
since the previous outburst. At super-outburst maximum the system was
at V ∼ 18, but in quiescence it is fainter than V ∼ 22, which will
make any detailed quiescent follow-up of this system difficult.

---------------------------------------------------------
Title: Stellar magnetic fields from four Stokes parameter observations
Authors: Rusomarov, N.; Kochukhov, O.; Piskunov, N.
2015IAUS..307..395R Altcode: 2014arXiv1407.7912R
Magnetic Doppler imaging (MDI) from observations of four Stokes
parameters can uncover new information that is of interest to the
evolution and structure of magnetic fields of intermediate and high-mass
stars. Our MDI study of the chemically peculiar star HD 24712 from four
Stokes parameter observations, obtained with the HARPSpol instrument
at the 3.6-m ESO telescope, revealed a magnetic field with strong
dipolar component and weak small-scale contributions. This finding
gives evidence for the hypothesis that old Ap stars have predominantly
dipolar magnetic fields.

---------------------------------------------------------
Title: Three-dimensional magnetic and abundance mapping of the cool
Ap star HD 24712. II. Two-dimensional magnetic Doppler imaging in
all four Stokes parameters
Authors: Rusomarov, N.; Kochukhov, O.; Ryabchikova, T.; Piskunov, N.
2015A&A...573A.123R Altcode: 2014arXiv1409.6955R
 Aims: We present a magnetic Doppler imaging study from all Stokes
parameters of the cool, chemically peculiar star HD 24712. This is
the very first such analysis performed at a resolving power exceeding
105. Methods: The analysis is performed on the basis
of phase-resolved observations of line profiles in all four Stokes
parameters obtained with the HARPSpol instrument attached at the 3.6
m ESO telescope. We used the magnetic Doppler imaging code invers10,
which allowed us to derive the magnetic field geometry and surface
chemical abundance distributions simultaneously. Results: We
report magnetic maps of HD 24712 recovered from a selection of Fe
i, Fe ii, Nd iii, and Na i lines with strong polarization signals
in all Stokes parameters. Our magnetic maps successfully reproduce
most of the details available from our observation data. We used
these magnetic field maps to produce abundance distribution map of
Ca. This new analysis shows that the surface magnetic field of HD
24712 has a dominant dipolar component with a weak contribution from
higher-order harmonics. The surface abundance distributions of Fe and
Ca show enhancements near the magnetic equator with an underabundant
patch at the visible (positive) magnetic pole; Nd is highly abundant
around the positive magnetic pole. The Na abundance map shows a high
overabundance around the negative magnetic pole. Conclusions:
Based on our investigation and similar recent magnetic mapping studies
that used four Stokes parameters, we present tentative evidence for
the hypothesis that Ap stars with dipole-like fields are older than
stars with magnetic fields that have more small-scale structures. We
find that our abundance maps are inconsistent with recent theoretical
calculations of atomic diffusion in presence of magnetic fields. Based on observations collected at the European Southern Observatory,
Chile (ESO programs 084.D-0338, 085.D-0296, 086.D-0240).

---------------------------------------------------------
Title: Methodology for measuring fundamental parameters and associated
uncertainties for middle and cool main-sequence stars
Authors: Piskunov, N.; Ryabchikova, T.; Titarenko, A.; Pakhomov,
Yu. V.; Nizamov, B.
2014psce.conf..130P Altcode:
We have performed a study of a representative group of main-sequence
stars in the temperature range 5000-10000 K in order to test our
methodology for determining fundamental parameters and for the
assesment of associated uncertainties. The stars selected have
reasonably well-established parameters. This paper presents all the
steps of our method, from the selection of spectral intervals and
atomic/molecular data, to the determination of effective temperatures,
surface gravities and metallicities.

---------------------------------------------------------
Title: Magnetic fields of Ap stars from full Stokes
spectropolarimetric observations
Authors: Rusomarov, N.; Kochukhov, O.; Piskunov, N.
2014psce.conf..380R Altcode: 2013arXiv1310.0664R
Current knowledge about stellar magnetic fields relies almost entirely
on observations of circular polarization. Few objects have been
observed in all four Stokes parameters. The magnetic Ap star HD 24712
(DO Eri, HR 1217) was recently observed in the Stokes IQUV parameters
with the HARPSpol instrument at the 3.6-m ESO telescope as part of our
project at investigating Ap stars in all four Stokes parameters. The
resulting spectra have dense phase coverage, resolving power &gt; 10^5,
and S/N ratio of 300-600. These are the highest quality full Stokes
observations obtained for any star other than the Sun. We present
preliminary results from magnetic Doppler imaging of HD 24712. This
analysis is the first step towards obtaining detailed 3-D maps of
magnetic fields and abundance structures for HD 24712 and for other
Ap stars that we are currently observing with HARPSpol.

---------------------------------------------------------
Title: Exoplanet Science with the European Extremely Large
Telescope. The Case for Visible and Near-IR Spectroscopy at High
Resolution
Authors: Udry, S.; Lovis, C.; Bouchy, F.; Collier Cameron, A.; Henning,
T.; Mayor, M.; Pepe, F.; Piskunov, N.; Pollacco, D.; Queloz, D.;
Quirrenbach, A.; Rauer, H.; Rebolo, R.; Santos, N. C.; Snellen, I.;
Zerbi, F.
2014arXiv1412.1048U Altcode:
Exoplanet science is booming. In 20 years our knowledge has expanded
considerably, from the first discovery of a Hot Jupiter, to the
detection of a large population of Neptunes and super-Earths,
to the first steps toward the characterization of exoplanet
atmospheres. Between today and 2025, the field will evolve at an even
faster pace with the advent of several space-based transit search
missions, ground-based spectrographs, high-contrast imaging facilities,
and the James Webb Space Telescope. Especially the ESA M-class PLATO
mission will be a game changer in the field. From 2024 onwards, PLATO
will find transiting terrestrial planets orbiting within the habitable
zones of nearby, bright stars. These objects will require the power
of Extremely Large Telescopes (ELTs) to be characterized further. The
technique of ground-based high-resolution spectroscopy is establishing
itself as a crucial pathway to measure chemical composition, atmospheric
structure and atmospheric circulation in transiting exoplanets. A
high-resolution spectrograph covering the visible and near-IR domains,
mounted on the European ELT, will be able to detect molecules such as
water vapour, carbon dioxide and oxygen in the atmospheres of habitable
planets under favourable circumstances. E-ELT HiRES is the perfect
ground-based match to the PLATO space mission and represents a unique
opportunity for Europe to lead the world into the era of exploration
of exoplanets with habitable conditions. HiRES will also be extremely
complementary to other E-ELT planned instruments specialising in
different kinds of planets, such as METIS and EPICS.

---------------------------------------------------------
Title: HIRES: the high resolution spectrograph for the E-ELT
Authors: Zerbi, F. M.; Bouchy, F.; Fynbo, J.; Maiolino, R.; Piskunov,
N.; Rebolo Lopez, R.; Santos, N.; Strassmeier, K.; Udry, S.; Vanzi,
L.; Riva, M.; Basden, A.; Boisse, I.; Bonfils, X.; Buscher, D.; Cabral,
A.; Dimarcantonio, P.; Di Varano, I.; Henry, D.; Monteiro, M.; Morris,
T.; Murray, G.; Oliva, Ernesto; Parry, I.; Pepe, F.; Quirrenbach, A.;
Rasilla, J. L.; Rees, P.; Stempels, E.; Valenziano, L.; Wells, M.;
Wildi, F.; Origlia, L.; Allende Prieto, C.; Chiavassa, A.; Cristiani,
S.; Figueira, P.; Gustafsson, B.; Hatzes, A.; Haehnelt, M.; Heng,
K.; Israelian, G.; Kochukhov, O.; Lovis, C.; Marconi, A.; Martins,
C. J. A. P.; Noterdaeme, P.; Petitjean, P.; Puzia, T.; Queloz, D.;
Reiners, A.; Zoccali, M.
2014SPIE.9147E..23Z Altcode:
The current instrumentation plan for the E-ELT foresees a High
Resolution Spectrograph conventionally indicated as HIRES. Shaped
on the study of extra-solar planet atmospheres, Pop-III stars and
fundamental physical constants, HIRES is intended to embed observing
modes at high-resolution (up to R=150000) and large spectral range
(from the blue limit to the K band) useful for a large suite of science
cases that can exclusively be tackled by the E-ELT. We present in
this paper the solution for HIRES envisaged by the "HIRES initiative",
the international collaboration established in 2013 to pursue a HIRES
on E-ELT.

---------------------------------------------------------
Title: Magnetic fields in M-dwarfs from high-resolution infrared
spectroscopy
Authors: Shulyak, D.; Reiners, A.; Seemann, U.; Kochukhov, O.;
Piskunov, N.
2014IAUS..302..170S Altcode:
Accurate spectroscopic measurements of magnetic fields in low mass
stars remain challenging because of their cool temperatures, strong
line blending, and often fast rotation. This is why previous estimates
were based either on the analysis of only a few lines or made use of
some indirect techniques. This frequently led to noticeable scatter in
obtained results. In this talk I will present and discuss new results
on the determination of the intensity and geometry of the magnetic
fields in M-dwarfs using IR observations obtained with CRIRES@VLT. The
instrument provides unprecedented data of high resolution (R = 100
000) which is crucial for resolving individual magnetically broadened
molecular and atomic lines. Such an in-depth analysis based on direct
magnetic spectral synthesis opens a possibility to deduce both field
intensity and geometry avoiding most of the limitation and assumptions
made in previous studies.

---------------------------------------------------------
Title: Wavelength calibration from 1-5μm for the CRIRES+
high-resolution spectrograph at the VLT
Authors: Seemann, U.; Anglada-Escude, G.; Baade, D.; Bristow, P.;
Dorn, R. J.; Follert, R.; Gojak, D.; Grunhut, J.; Hatzes, A. P.;
Heiter, U.; Ives, D. J.; Jeep, P.; Jung, Y.; Käufl, H. -U.; Kerber,
F.; Klein, B.; Lizon, J. -L.; Lockhart, M.; Löwinger, T.; Marquart,
T.; Oliva, E.; Paufique, J.; Piskunov, N.; Pozna, E.; Reiners, A.;
Smette, A.; Smoker, J.; Stempels, E.; Valenti, E.
2014SPIE.9147E..5GS Altcode:
CRIRES at the VLT is one of the few adaptive optics enabled instruments
that offer a resolving power of 105 from 1 - 5 μm. An
instrument upgrade (CRIRES+) is proposed to implement cross-dispersion
capabilities, spectro-polarimetry modes, a new detector mosaic, and a
new gas absorption cell. CRIRES+ will boost the simultaneous wavelength
coverage of the current instrument (~ γ/70 in a single-order) by a
factor of 10 in the cross-dispersed configuration, while still retaining
a ~&gt; 10 arcsec slit suitable for long-slit spectroscopy. CRIRES+
dramatically enhances the instrument's observing efficiency, and
opens new scientific opportunities. These include high-precision
radial-velocity studies on the 3 m/s level to characterize extra-solar
planets and their athmospheres, which demand for specialized, highly
accurate wavelength calibration techniques. In this paper, we present a
newly developed absorption gas-cell to enable high-precision wavelength
calibration for CRIRES+. We also discuss the strategies and developments
to cover the full operational spectral range (1 - 5 μµm), employing
cathode emission lamps, Fabry-Perot etalons, and absorption gas-cells.

---------------------------------------------------------
Title: Magnetic fields of Ap stars from full Stokes vector
spectropolarimetric observations
Authors: Rusomarov, N.; Kochukhov, O.; Piskunov, N.
2014IAUS..302..304R Altcode: 2013arXiv1310.0412R
Current knowledge about stellar magnetic fields relies almost entirely
on circular polarization observations, with very few objects having been
observed in all four Stokes parameters. We are investigating a sample
of Ap stars in all four Stokes parameters using the HARPSpol instrument
at the 3.6-m ESO telescope. In the context of this project we recently
observed the magnetic Ap star HD 24712 (DO Eri, HR 1217). The resulting
spectra have dense phase coverage, resolving power &gt; 105,
and S/N ratio of 300-600. These are the highest quality full Stokes
observations obtained for any star other than the Sun. Furthermore, we
have achieved good phase coverage for HD 125248 and HD 119419. Typical
four Stokes parameters HARPSpol spectra are shown in Fig. 1. An analysis
of the full Stokes vector spectropolarimetric data set of HD 24712
has been published in Rusomarov et al. (2013).

---------------------------------------------------------
Title: Opto-mechanical design of a new cross dispersion unit for
the CRIRES+ high resolution spectrograph for the VLT
Authors: Lizon, Jean Louis; Klein, Barbara; Oliva, Ernesto; Löwinger,
Tom; Anglada Escude, Guillem; Baade, Dietrich; Bristow, Paul; Dorn,
Reinhold J.; Follert, Roman; Grunhut, Jason; Hatzes, Artie; Heiter,
Ulrike; Ives, Derek; Jung, Yves; Kerber, Florian; Lockhart, Matt;
Marquart, Thomas; Origlia, Livia; Pasquini, Luca; Paufique, Jerome;
Piskunov, N.; Pozna, Eszter; Reiners, Ansgar; Smette, Alain; Smoker,
Jonathan; Seemann, Ulf; Stempels, Eric; Valenti, Elena
2014SPIE.9147E..7SL Altcode:
CRIRES is one of the few IR (0.92-5.2 μm) high-resolution spectrographs
in operation at the VLT since 2006. Despite good performance it
suffers a limitation that significantly hampers its ability: a small
spectral coverage per exposure. The CRIRES upgrade (CRIRES+) proposes to
transform CRIRES into a cross-dispersed spectrograph while maintaining
the high resolution (100000) and increasing the wavelength coverage
by a factor 10 compared to the current capabilities. A major part of
the upgrade is the exchange of the actual cryogenic pre-disperser
module by a new cross disperser unit. In addition to a completely
new optical design, a number of important changes are required on key
components and functions like the slit unit and detectors units. We will
outline the design of these new units fitting inside a predefined and
restricted space. The mechanical design of the new functions including
a description and analysis will be presented. Finally we will present
the strategy for the implementation of the changes.

---------------------------------------------------------
Title: Concept and optical design of the cross-disperser module
for CRIRES+
Authors: Oliva, E.; Tozzi, A.; Ferruzzi, D.; Origlia, L.; Hatzes,
A.; Follert, R.; Löwinger, T.; Piskunov, N.; Heiter, U.; Lockhart,
M.; Marquart, T.; Stempels, E.; Reiners, A.; Anglada-Escude, G.;
Seemann, Ulf; Dorn, R. J.; Bristow, P.; Baade, D.; Delabre, B.; Gojak,
D.; Grunhut, J.; Klein, Barbara; Hilker, M.; Ives, D. J.; Jung, Y.;
Kaeufl, H. -U.; Kerber, F.; Lizon, J. L.; Pasquini, L.; Paufique,
J.; Pozna, Eszter; Smette, A.; Smoker, J.; Valenti, E.
2014SPIE.9147E..7RO Altcode: 2014arXiv1407.3057O
CRIRES, the ESO high resolution infrared spectrometer, is a unique
instrument which allows astronomers to access a parameter space which
up to now was largely uncharted. In its current setup, it consists
of a single-order spectrograph providing long-slit, single-order
spectroscopy with resolving power up to R=100,000 over a quite
narrow spectral range. This has resulted in sub-optimal efficiency
and use of telescope time for all the scientific programs requiring
broad spectral coverage of compact objects (e.g. chemical abundances
of stars and intergalactic medium, search and characterization of
extra-solar planets). To overcome these limitations, a consortium
was set-up for upgrading CRIRES to a cross-dispersed spectrometer,
called CRIRES+. This paper presents the updated optical design of the
cross-dispersion module for CRIRES+. This new module can be mounted in
place of the current pre-disperser unit. The new system yields a factor
of &gt;10 increase in simultaneous spectral coverage and maintains a
quite long slit (10"), ideal for observations of extended sources and
for precise sky-background subtraction.

---------------------------------------------------------
Title: CRIRES+: a cross-dispersed high-resolution infrared
spectrograph for the ESO VLT
Authors: Follert, R.; Dorn, R. J.; Oliva, E.; Lizon, J. L.; Hatzes,
A.; Piskunov, N.; Reiners, A.; Seemann, U.; Stempels, E.; Heiter, U.;
Marquart, T.; Lockhart, M.; Anglada-Escude, G.; Löwinger, T.; Baade,
D.; Grunhut, J.; Bristow, P.; Klein, B.; Jung, Y.; Ives, D. J.; Kerber,
F.; Pozna, E.; Paufique, J.; Kaeufl, H. U.; Origlia, L.; Valenti,
E.; Gojak, D.; Hilker, M.; Pasquini, L.; Smette, A.; Smoker, J.
2014SPIE.9147E..19F Altcode:
High-resolution infrared spectroscopy plays an important role in
astrophysics from the search for exoplanets to cosmology. Yet,
many existing infrared spectrographs are limited by a rather small
simultaneous wavelength coverage. The AO assisted CRIRES instrument,
installed at the ESO VLT on Paranal, is one of the few IR (0.92-5.2
μm) highresolution spectrographs in operation since 2006. However it
has a limitation that hampers its efficient use: the wavelength range
covered in a single exposure is limited to ~15 nanometers. The CRIRES
Upgrade project (CRIRES+) will transform CRIRES into a cross-dispersed
spectrograph and will also add new capabilities. By introducing
crossdispersion elements the simultaneously covered wavelength range
will be increased by at least a factor of 10 with respect to the
present configuration, while the operational wavelength range will
be preserved. For advanced wavelength calibration, new custom made
absorption gas cells and etalons will be added. A spectro-polarimetric
unit will allow one for the first time to record circularly polarized
spectra at the highest spectral resolution. This will be all supported
by a new data reduction software which will allow the community to
take full advantage of the new capabilities of CRIRES+.

---------------------------------------------------------
Title: Novel infrared polarimeter for the ESO CRIRES+ instrument
Authors: Lockhart, Matthew; Piskunov, Nikolai; Stempels, Eric; Escuti,
Michael; Oliva, Ernesto; Käufl, Hans-Ulrich; Heiter, Ulrike; Marquart,
Thomas; Anglada-Escude, Guillem; Baade, Dietrich; Bristow, Paul;
Dorn, Reinhold J.; Follert, Roman; Gojak, Domingo; Grunhut, Jason
H.; Hatzes, Artie; Hilker, Michael; Ives, Derek; Jung, Yves; Kerber,
Florian; Klein, Barbara; Lizon, Jean-Louis; Löwinger, Tom; Origlia,
Livia; Pasquini, Luca; Paufique, Jerome; Pozna, Eszter; Reiners,
Ansgar; Seemann, Ulf; Smette, Alain; Smoker, Jonathan; Valenti, Elena
2014SPIE.9147E..8PL Altcode:
The CRIRES infrared spectrograph at the European Southern Observatory
(ESO) Very Large Telescope (VLT) facility will soon receive an
upgrade. This upgrade will include the addition of a module for
performing highresolution spectropolarimetry. The polarimetry module
will incorporate a novel infrared beamsplitter based on polarization
gratings (PGs). The beamsplitter produces a pair of infrared output
beams, with opposite circular polarizations, which are then fed into
the spectrograph. Visible light passes through the module virtually
unaltered and is then available for use by the CRIRES adaptive optics
system. We present the design of the polarimetry module and measurements
of PG behavior in the 1 to 2.7 μm wavelength range.

---------------------------------------------------------
Title: CRIRES+: Exploring the Cold Universe at High Spectral
Resolution
Authors: Dorn, R. J.; Anglada-Escude, G.; Baade, D.; Bristow, P.;
Follert, R.; Gojak, D.; Grunhut, J.; Hatzes, A.; Heiter, U.; Hilker,
M.; Ives, D. J.; Jung, Y.; Käufl, H. -U.; Kerber, F.; Klein, B.;
Lizon, J. -L.; Lockhart, M.; Löwinger, T.; Marquart, T.; Oliva,
E.; Origlia, L.; Pasquini, L.; Paufique, J.; Piskunov, N.; Pozna,
E.; Reiners, A.; Smette, A.; Smoker, J.; Seemann, U.; Stempels, E.;
Valenti, E.
2014Msngr.156....7D Altcode:
The CRIRES upgrade project, CRIRES+, transforms this VLT instrument
into a cross-dispersed spectrograph to increase the wavelength range
that is covered simultaneously by a factor of ten. In addition, a
new detector focal plane array of three Hawaii 2RG detectors with a
5.3 μm cut-off wavelength will replace the existing detectors. For
advanced wavelength calibration, custom-made absorption gas cells
will be added. A spectropolarimetric unit will allow circularly
polarised spectra to be recorded. These upgraded capabilities will be
all supported by dedicated data reduction software which will allow
the community to take full advantage of the new capabilities offered
by CRIRES+.

---------------------------------------------------------
Title: Exploring the magnetic field complexity in M dwarfs at the
boundary to full convection
Authors: Shulyak, D.; Reiners, A.; Seemann, U.; Kochukhov, O.;
Piskunov, N.
2014A&A...563A..35S Altcode: 2014arXiv1401.5250S
Context. Magnetic fields play a pivotal role in the formation and
evolution of low-mass stars, but the dynamo mechanisms generating
these fields are poorly understood. Measuring cool star magnetism
is a complicated task because of the complexity of cool star spectra
and the subtle signatures of magnetic fields. Aims: Based on
detailed spectral synthesis, we carry out quantitative measurements
of the strength and complexity of surface magnetic fields in the
four well-known M dwarfs <ASTROBJ>GJ 388</ASTROBJ>, <ASTROBJ>GJ
729</ASTROBJ>, <ASTROBJ>GJ 285</ASTROBJ>, and <ASTROBJ>GJ 406</ASTROBJ>
that populate the mass regime around the boundary between partially
and fully convective stars. Very high-resolution (R = 100 000),
high signal-to-noise (up to 400), near-infrared Stokes I spectra were
obtained with CRIRES at ESO's Very Large Telescope covering regions of
the FeH Wing-Ford transitions at 1μm and Na i lines at 2.2μm. Methods: A modified version of the Molecular Zeeman Library (MZL)
was used to compute Landé g-factors for FeH lines. We determined
the distribution of magnetic fields by magnetic spectral synthesis
performed with the Synmast code. We tested two different magnetic
geometries to probe the influence of field orientation effects. 
Results: Our analysis confirms that FeH lines are excellent indicators
of surface magnetic fields in low-mass stars of type M, particularly in
comparison to profiles of Na i lines that are heavily affected by water
lines and that suffer problems with continuum normalization. The field
distributions in all four stars are characterized by three distinct
groups of field components, and the data are consistent neither with a
smooth distribution of different field strengths nor with one average
field strength covering the full star. We find evidence of a subtle
difference in the field distribution of GJ 285 compared to the other
three targets. GJ 285 also has the highest average field of 3.5 kG
and the strongest maximum field component of 7-7.5 kG. The maximum
local field strengths in our sample seem to be correlated with rotation
rate. While the average field strength is saturated, the maximum local
field strengths in our sample show no evidence of saturation. 
Conclusions: We find no difference between the field distributions of
partially and fully convective stars. The one star with evidence of
field distribution different from the other three is the most active
star (i.e. with X-ray luminosity and mean surface magnetic field)
rotating relatively fast. A possible explanation is that rotation
determines the distribution of surface magnetic fields, and that local
field strengths grow with rotation even in stars in which the average
field is already saturated. Based on observations collected at the
European Southern Observatory, Paranal, Chile (programme 385.D-0273).

---------------------------------------------------------
Title: Doppler images of DI Piscium during 2004-2006
Authors: Lindborg, M.; Hackman, T.; Mantere, M. J.; Korhonen, H.;
Ilyin, I.; Kochukhov, O.; Piskunov, N.
2014A&A...562A.139L Altcode:
 Aims: <ASTROBJ>DI Psc</ASTROBJ> (<ASTROBJ>HD 217352</ASTROBJ>)
is a Li-rich, rapidly rotating single K giant. We set out to study the
spot configuration and activity level by calculating surface temperature
maps of the star. Methods: We apply the Doppler imaging method on
high-resolution optical spectroscopy obtained during 2004-2006. 
Results: In July-August 2004, no clear spot structures were visible,
but the spot coverage increased in July 2005, and cool spots emerged,
especially at intermediate latitudes. Later on in September 2006, the
spot coverage increased and cool spots were visible on both sides of
the equator. However, the map of 2006 suffers from bad phase coverage,
meaning it is not possible to draw definite conclusions on the spot
locations during that season. Conclusions: Compared with earlier
Doppler maps of DI Psc and temperature maps obtained for other late-type
stars with similar rotation rates, DI Psc seems to be in a low activity
state especially during the observing season of July-August 2004. During
the 2005 and 2006 observing seasons, the spot activity seen in the
spectral line profiles and inferred from Doppler images increases,
and the temperature contrast in our last map is more comparable to what
was reported in an earlier study. Therefore, it can be concluded that
the spot activity level of the star is variable over time. However,
the present and previous Doppler images form too short a time series to
draw conclusions about a possible activity cycle in DI Psc. Based
on observations made with the Nordic Optical Telescope, operated on
the island of La Palma jointly by Denmark, Finland, Iceland, Norway,
and Sweden in the Spanish Observatorio del Roque de los Muchachos of
the Instituto de Astrofísica de Canarias.

---------------------------------------------------------
Title: A Gentle Introduction to SME
Authors: Piskunov, Nikolai
2014dapb.book..287P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Testing SME determination of stellar parameters
Authors: Ryabchikova, T. A.; Mashonkina, L. I.; Titarenko, A. R.;
Alexeeva, S. A.; Pakhomov, Yu. V.; Piskunov, N. E.; Sitnova, T. M.;
Nizamov, B. A.
2014IAUS..298..436R Altcode:
We present the results of special tests of the automatic procedure
for atmospheric parameters determination based on spectroscopy.

---------------------------------------------------------
Title: Three-dimensional magnetic and abundance mapping of the cool
Ap star HD 24712 . I. Spectropolarimetric observations in all four
Stokes parameters
Authors: Rusomarov, N.; Kochukhov, O.; Piskunov, N.; Jeffers, S. V.;
Johns-Krull, C. M.; Keller, C. U.; Makaganiuk, V.; Rodenhuis, M.;
Snik, F.; Stempels, H. C.; Valenti, J. A.
2013A&A...558A...8R Altcode: 2013arXiv1306.0997R
Context. High-resolution spectropolarimetric observations provide
simultaneous information about stellar magnetic field topologies and
three-dimensional distributions of chemical elements. High-quality
spectra in the Stokes IQUV parameters are currently available for very
few early-type magnetic chemically peculiar stars. Here we present
analysis of a unique full Stokes vector spectropolarimetric data
set, acquired for the cool magnetic Ap star HD 24712 with a recently
commissioned spectropolarimeter. Aims: The goal of our work
is to examine the circular and linear polarization signatures inside
spectral lines and to study variation of the stellar spectrum and
magnetic observables as a function of rotational phase. Methods:
HD 24712 was observed with the HARPSpol instrument at the 3.6-m ESO
telescope over a period of 2010-2011. We achieved full rotational phase
coverage with 43 individual Stokes parameter observations. The resulting
spectra have a signal-to-noise ratio of 300-600 and resolving power
exceeding 105. The multiline technique of least-squares
deconvolution (LSD) was applied to combine information from the
spectral lines of Fe-peak and rare earth elements. Results: We
used the HARPSPol spectra of HD 24712 to study the morphology of the
Stokes profile shapes in individual spectral lines and in LSD Stokes
profiles corresponding to different line masks. From the LSD Stokes V
profiles we measured the longitudinal component of the magnetic field,
⟨Bz⟩, with an accuracy of 5-10 G. We also determined the
net linear polarization from the LSD Stokes Q and U profiles. Combining
previous ⟨Bz⟩ measurements with our data allowed us to
determine an improved rotational period of the star, Prot
= 12.45812 ± 0.00019 d. We also measured the longitudinal
magnetic field from the cores of Hα and Hβ lines. The analysis of
⟨Bz⟩ measurements showed no evidence for a significant
radial magnetic field gradient in the atmosphere of HD 24712. We used
our ⟨Bz⟩ and net linear polarization measurements to
determine parameters of the dipolar magnetic field topology. We found
that magnetic observables can be reasonably well reproduced by the
dipolar model, although significant discrepancies remain at certain
rotational phases. We discovered rotational modulation of the Hα
core and related it to a non-uniform surface distribution of rare
earth elements. Based on observations collected at the European
Southern Observatory, Chile (ESO programs 084.D-0338, 085.D-0296,
086.D-0240).Figure 3 and Appendix A are available in electronic form
at <A href="http://www.aanda.org">http://www.aanda.org</A>

---------------------------------------------------------
Title: Are there tangled magnetic fields on HgMn stars?
Authors: Kochukhov, O.; Makaganiuk, V.; Piskunov, N.; Jeffers, S. V.;
Johns-Krull, C. M.; Keller, C. U.; Rodenhuis, M.; Snik, F.; Stempels,
H. C.; Valenti, J. A.
2013A&A...554A..61K Altcode: 2013arXiv1304.6717K
Context. Several recent spectrophotometric studies failed to detect
significant global magnetic fields in late-B HgMn chemically peculiar
stars, but some investigations have suggested the presence of strong
unstructured or tangled fields in these objects. Aims: We used
detailed spectrum synthesis analysis to search for evidence of tangled
magnetic fields in high-quality observed spectra of eight slowly
rotating HgMn stars and one normal late-B star. We also evaluated
recent sporadic detections of weak longitudinal magnetic fields in
HgMn stars based on the moment technique. Methods: Our spectrum
synthesis code calculated the Zeeman broadening of metal lines in HARPS
spectra, assuming an unstructured, turbulent magnetic field. A simple
line formation model with a homogeneous radial field distribution was
applied to assess compatibility between previous longitudinal field
measurements and the observed mean circular polarization signatures. Results: Our analysis of the Zeeman broadening of magnetically
sensitive spectral lines reveals no evidence of tangled magnetic fields
in any of the studied HgMn or normal stars. We infer upper limits
of 200-700 G for the mean magnetic field modulus - much smaller than
the field strengths implied by studies based on differential magnetic
line intensification and quadratic field diagnostics. The new HARPSpol
longitudinal field measurements for the extreme HgMn star HD 65949 and
the normal late-B star 21 Peg are consistent with zero at a precision of
3-6 G. Re-analysis of our Stokes V spectra of the spotted HgMn star HD
11753 shows that the recent moment technique measurements retrieved from
the same data are incompatible with the lack of circular polarization
signatures in the spectrum of this star. Conclusions: We conclude
that there is no evidence for substantial tangled magnetic fields on
the surfaces of studied HgMn stars. We cannot independently confirm
the presence of very strong quadratic or marginal longitudinal fields
for these stars, so results from the moment technique are likely to be
spurious. Based on observations collected at the European Southern
Observatory, Chile (ESO programmes 084.D-0338, 085.D-0296, 086.D-0240).

---------------------------------------------------------
Title: Radial velocity signatures of Zeeman broadening
Authors: Reiners, A.; Shulyak, D.; Anglada-Escudé, G.; Jeffers,
S. V.; Morin, J.; Zechmeister, M.; Kochukhov, O.; Piskunov, N.
2013A&A...552A.103R Altcode: 2013arXiv1301.2951R
Stellar activity signatures such as spots and plages can significantly
limit the search for extrasolar planets. Current models of
activity-induced radial velocity (RV) signals focus on the impact
of temperature contrast in spots according to which they predict the
signal to diminish toward longer wavelengths. The Zeeman effect on RV
measurements counteracts this: the relative importance of the Zeeman
effect on RV measurements should grow with wavelength because the
Zeeman displacement itself grows with λ, and because a magnetic and
cool spot contributes more to the total flux at longer wavelengths. In
this paper, we model the impact of active regions on stellar RV
measurements including both temperature contrast in spots and line
broadening by the Zeeman effect. We calculate stellar line profiles
using polarized radiative transfer models including atomic and molecular
Zeeman splitting over large wavelength regions from 0.5 to 2.3 μm. Our
results show that the amplitude of the RV signal caused by the Zeeman
effect alone can be comparable to that caused by temperature contrast;
a spot magnetic field of ~1000 G can produce a similar RV amplitude
as a spot temperature contrast of ~1000 K. Furthermore, the RV signal
caused by cool and magnetic spots increases with wavelength, in contrast
to the expectation from temperature contrast alone. We also calculate
the RV signal caused by variations in average magnetic field strength
from one observation to the next, for example due to a magnetic cycle,
but find it unlikely that this can significantly influence the search
for extrasolar planets. As an example, we derive the RV amplitude
of the active M dwarf AD Leo as a function of wavelength using data
from the HARPS spectrograph. Across this limited wavelength range, the
RV signal does not diminish at longer wavelengths but shows evidence
for the opposite behavior, consistent with a strong influence of the
Zeeman effect. We conclude that the RV signal of active stars does not
vanish at longer wavelength but sensitively depends on the combination
of spot temperature and magnetic field; in active low-mass stars,
it is even likely to grow with wavelength.

---------------------------------------------------------
Title: Multi-element Doppler imaging of the CP2 star HD 3980
Authors: Nesvacil, N.; Lüftinger, T.; Shulyak, D.; Obbrugger, M.;
Weiss, W.; Drake, N. A.; Hubrig, S.; Ryabchikova, T.; Kochukhov, O.;
Piskunov, N.; Polosukhina, N.
2013arXiv1303.2703N Altcode:
In atmospheres of magnetic main-sequence stars, the diffusion of
chemical elements leads to a number of observed anomalies, such
as abundance spots across the stellar surface. The aim of this
study was to derive a detailed picture of the surface abundance
distribution of the magnetic chemically peculiar star HD 3980. Based
on high-resolution, phase-resolved spectroscopic observations of the
magnetic A-type star HD 3980, the inhomogeneous surface distribution of
13 chemical elements (Li, O, Si, Ca, Cr, Mn, Fe, La, Ce, Pr, Nd, Eu,
and Gd) has been reconstructed. The INVERS12 code was used to invert
the rotational variability in line profiles to elemental surface
distributions. Assuming a centered, dominantly dipolar magnetic
field configuration, we find that Li, O, Mg, Pr, and Nd are mainly
concentrated in the area of the magnetic poles and depleted in the
regions around the magnetic equator. The high abundance spots of Si,
La, Ce, Eu, and Gd are located between the magnetic poles and the
magnetic equator. Except for La, which is clearly depleted in the
area of the magnetic poles, no obvious correlation with the magnetic
field has been found for these elements otherwise. Ca, Cr, and Fe
appear enhanced along the rotational equator and the area around
the magnetic poles. The intersection between the magnetic and the
rotational equator constitutes an exception, especially for Ca and Cr,
which are depleted in that region. No obvious correlation between the
theoretically predicted abundance patterns and those determined in this
study could be found. This can be attributed to a lack of up-to-date
theoretical models, especially for rare earth elements.

---------------------------------------------------------
Title: Magnetically Controlled Accretion on the Classical T Tauri
Stars GQ Lupi and TW Hydrae
Authors: Johns-Krull, Christopher M.; Chen, Wei; Valenti, Jeff A.;
Jeffers, Sandra V.; Piskunov, Nikolai E.; Kochukhov, Oleg; Makaganiuk,
V.; Stempels, H. C.; Snik, Frans; Keller, Christoph; Rodenhuis, M.
2013ApJ...765...11J Altcode: 2013arXiv1301.3182J
We present high spectral resolution (R ≈ 108, 000) Stokes V
polarimetry of the classical T Tauri stars (CTTSs) GQ Lup and TW Hya
obtained with the polarimetric upgrade to the HARPS spectrometer on
the ESO 3.6 m telescope. We present data on both photospheric lines
and emission lines, concentrating our discussion on the polarization
properties of the He I emission lines at 5876 Å and 6678 Å. The He
I lines in these CTTSs contain both narrow emission cores, believed
to come from near the accretion shock region on these stars, and broad
emission components which may come from either a wind or the large-scale
magnetospheric accretion flow. We detect strong polarization in the
narrow component of the two He I emission lines in both stars. We
observe a maximum implied field strength of 6.05 ± 0.24 kG in the
5876 Å line of GQ Lup, making it the star with the highest field
strength measured in this line for a CTTS. We find field strengths in
the two He I lines that are consistent with each other, in contrast to
what has been reported in the literature on at least one star. We do
not detect any polarization in the broad component of the He I lines
on these stars, strengthening the conclusion that they form over a
substantially different volume relative to the formation region of
the narrow component of the He I lines.

---------------------------------------------------------
Title: DELO-Bezier Formal Solutions of the Polarized Radiative
Transfer Equation
Authors: de la Cruz Rodríguez, J.; Piskunov, N.
2013ApJ...764...33D Altcode: 2012arXiv1212.2737D
We present two new accurate and efficient methods to compute the
formal solution of the polarized radiative transfer equation. In this
work, the source function and the absorption matrix are approximated
using quadratic and cubic Bezier spline interpolants. These schemes
provide second- and third-order approximations, respectively, and
do not suffer from erratic behavior of the polynomial approximation
(overshooting). The accuracy and the convergence of the new method are
studied along with other popular solutions of the radiative transfer
equation, using stellar atmospheres with strong gradients in the
line-of-sight velocity and in the magnetic-field vector.

---------------------------------------------------------
Title: MMT Hectochelle Spectral Variability of Active Late-type
Stars in the Kepler Field (2013A)
Authors: Brown, Alexander; Walkowicz, Lucianne; Saar, Steven; Hawley,
Suzanne; Kowalski, Adam; Furesz, Gabor; Piskunov, Nikolai
2013noao.prop..286B Altcode:
We have on-going it Kepler photometric monitoring of over 300 active
late-type (mid-A - K) stars as part of our Cycles 1/2/3/4 Guest
Observer (GO) programs with the aim of studying starspot evolution,
differential rotation, activity cycles, and flares. We propose to
use the MMT Hectochelle multiobject spectrograph to observe over
140 of these stars to determine a range of basic physical properties
for the stars, such as radial velocity variations due to binarity,
chromospheric activity levels from Ca II H+K and H(alpha), projected
rotational velocities for comparison to the rotational periods
measured directly by it Kepler, age/youth as indicated by Li I, and
better effective temperature and luminosity estimates. In addition,
to provide a superior sample for statistical studies another 800 GKM
dwarf stars showing either starspot modulation from the it Kepler
Team's data or from our deep XMM X-ray survey will be observed using
the unassigned fibers in each field. These measurements require the
32,000 spectral resolution provided by Hectochelle, which is hard to
obtain efficiently for 13-15th magnitude stars any other way.

---------------------------------------------------------
Title: A Large Sample of Magnetically-Active Stars Observed With
Kepler
Authors: Wells, Mark; Neff, J. E.; Brown, A.; Ayres, T. R.; Basri,
G. S.; Berdyugina, S.; Harper, G.; Hawley, S. L.; Korhonen, H.;
Kowalski, A.; Micela, G.; Piskunov, N. E.; Ramsey, L. W.; Saar, S. H.;
Walkowicz, L. M.
2013AAS...22135415W Altcode:
We have observed about 325 stars in our Kepler Guest Observer
programs (Cycles 1 through 4). For most of these targets, we are
analyzing extremely high-precision light curves that have been
continuously sampled every 30 minutes for up to 3 years. Our sample
of candidate magnetically-active stars was selected primarily using
GALEX colors. Starspots, pulsations, and variations due to eclipsing
and contact binaries combine to produce a rich variety of light
curves. We have developed semi-automated procedures to characterize
this variability and thus to classify the targets and identify the
physical mechanisms that dominate their Kepler light curves. We will
describe these procedures and discuss the range of physical properties
covered by our final classification scheme. We are using this Kepler
database of variability over timescales of minutes to years to provide
diagnostics of flares, starspot formation, evolution, migration, and
ultimately of stellar cycles in general. This work contains results
obtained using the NASA Kepler satellite and from the Apache Point
Observatory, the MMT (using NOAO community access time), and the
Hobby-Eberly Telescope. Funding is provided by NASA Kepler grants
NNX10AC51G, NNX11AC79G, and NNX12AC85G to the University of Colorado,
by NSF grant AST-1109695 to the College of Charleston, and by a grant
from the South Carolina Space Grant consortium.

---------------------------------------------------------
Title: HARPS Spectropolarimetry of the Classical T Tauri Stars GQ
Lup and TW Hya
Authors: Johns-Krull, Christopher M.; Chen, W.; Valenti, J. A.;
Jeffers, S. V.; Piskunov, N. E.; Kochukhov, O.; Makaganiuk, V.;
Stempels, H. C.; Snik, F.; Keller, C.; Rodenhuis, M.
2013AAS...22125614J Altcode:
We present high spectral resolution Stokes V polarimetery of the
Classical T Tauri stars (CTTSs) GQ Lup and TW Hya obtained with
the polarimetric upgrade to the HARPS spectrometer on the ESO 3.6 m
telescope. We present data on both photospheric lines and emission
lines, concentrating our discussion on the polarization properties
of the He I emission lines at 5876 A and 6678 A. The He I lines
in both these CTTS contain both narrow emission cores, believed to
come from near the accretion shock region on these stars, and broad
emission components which may come from either a wind or the large
scale magnetospheric accretion flow. We detect strong polarization in
the narrow component of both the He I emission lines in both stars. We
observe a maximum implied field strength of 5.8 +/- 0.3 kG in the 5876
A line of GQ Lup, the highest field strength measured to date in this
line for a CTTS. We find field strengths in the two He I lines that
are consistent with each other, unlike what has been reported in the
literature on at least one star. We do not detect any polarization in
the broad component of the He I lines on these stars, strengthening
the conclusion that they form over a substantially different volume
relative the formation region of the narrow component of the He I lines.

---------------------------------------------------------
Title: VizieR Online Data Catalog: Exoplanet Orbit Database (Wright+,
2011)
Authors: Wright, J. T.; Kakhouri, O.; Marcy, G. W.; Han, E.; Feng,
Y.; Johnson, J. A.; Howard, A. W.; Fischer, D. A.; Valenti, J. A.;
Anderson, J.; Piskunov, N.
2013yCat..61230412W Altcode:
We present a database of well determined orbital parameters of
exoplanets, and their host stars' properties. This database comprises
spectroscopic orbital elements measured for 427 planets orbiting 363
stars from radial velocity and transit measurements as reported in
the literature. We have also compiled fundamental transit parameters,
stellar parameters, and the method used for the planets discovery. This
Exoplanet Orbit Database includes all planets with robust, well measured
orbital parameters reported in peer-reviewed articles. The Database is
available in a searcheable, filterable, and sortable form on the Web
at http://exoplanets.org through the Exoplanets Data Explorer Table,
and the data can be plotted and explored through the Exoplanet Data
Explorer Plotter. We use the Data Explorer to generate publication-ready
plots giving three examples of the signatures of exoplanet migration
and dynamical evolution: We illustrate the character of the apparent
correlation between mass and period in exoplanet orbits, the different
selection biases between radial velocity and transit surveys, and that
the multiplanet systems show a distinct semi-major axis distribution
from apparently singleton systems. (2 data files).

---------------------------------------------------------
Title: Young Star Populations in the Kepler Field
Authors: Brown, Alexander; Neff, J. E.; Wells, M.; Saar, S.; Furesz,
G.; Walkowicz, L. M.; Ayres, T. R.; Basri, G. S.; Berdyugina, S.;
Harper, G.; Hawley, S. L.; Korhonen, H.; Kowalski, A.; Micela, G.;
Piskunov, N. E.; Ramsey, L. W.
2013AAS...22135414B Altcode:
The Kepler satellite is providing spectacular optical photometric
light-curves of unprecedented precision and duration that routinely
allow detailed studies of stellar magnetic activity on late-type stars
that were difficult previously. Kepler provides multi-year duration
light-curves that allow investigation of how activity phenomena --
such as the growth, migration, and decay of star-spots, differential
rotation, activity cycles, and flaring -- operate on a wide variety of
single and binary stars. The 105 square degree Kepler Field contains
tens of thousands of late-type stars showing rotational modulation due
to star-spots with periods ranging from one day to a “solar-like”
month. Short rotation periods and high levels of magnetic activity are
strongly correlated. However, there are only two basic reasons why stars
with rotation periods of a few days possess such high angular momentum
--- either they are close binaries or they are young stars. During
Kepler GO Cycles 1 through 4 we have been studying the Long-cadence
(30 minute sampling) photometry of hundreds of active late-type stars
and as an absolutely essential complement we have been obtaining high
resolution optical spectra to understand the physical properties of
these stars. We present results from a spectroscopic survey using the
MMT Hectochelle multi-object echelle of 4 square degrees of the Kepler
Field. We have discovered a significant population of young stars with
Li I absorption indicating ages of ~100 Myr or less at a spatial density
of at least 20 stars per square degree. Our detected young star sample
comprises at least 80 stars and represents a dramatic advance compared
to the previously known sample over the full Kepler Field of three
stars in this age range. Roughly one sixth of the stars observed are
young and a similar number short-period binaries based on 2-4 radial
velocities. We show how the rotational properties of the stars and their
physical properties are related. This work is based on data obtained
with the NASA Kepler satellite and the MMT Hectochelle spectrograph
using NOAO community access time. Support by NASA Kepler grants to the
University of Colorado and by NSF grant to the College of Charleston.

---------------------------------------------------------
Title: Upgrading CRIRES-VLT to cross-dispersed mode
Authors: Oliva, E.; Hatzes, A.; Piskunov, N.; Reiners, A.; Käufl,
H. U.; Ferruzzi, D.; Tozzi, A.; Origlia, L.
2012SPIE.8446E..2NO Altcode:
The cryogenic high resolution IR echelle spectrograph CRIRES is the
ESO infrared (0.95&amp;#87225.4 μm) high resolution spectrograph
operating at the Nasmyth A focus of VLT-UT1. The instrument provides
long-slit (31") spectroscopy with resolving power up to R=100,000
over a quite narrow wavelengths range, about 1/70 of the central
wavelength. Observations of compact objects (e.g. stellar photospheres)
could be made much more efficient by implementing a cross-dispersed
mode, which increases the simultaneous spectral coverage by an order
of magnitude or more. This paper presents the design of a relatively
simple system to add cross-dispersed modes to CRIRES with a minimum
impact on the instrument optics and mechanics.

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Title: “Virtual Atomic and Molecular Data Centre” and Astrophysics:
Level 2 Release
Authors: Doronin, M.; Dubernet, M. L.; Walton, N.; Mason, N.; Rixon,
G.; Sidaner, P. L.; Schlemmer, S.; Piskunov, N.; Tennyson, J.; Akram,
A.; Endres, C.; Hill, C.; Marquart, T.; Nenadovic, L.; Smith, K.;
Vamdc Consortium
2012ASPC..461..331D Altcode: 2012adass..21..331D
The Virtual Atomic and Molecular Data Centre (VAMDC, &lt;a
href='http://www.vamdc.eu/'&gt;http://www.vamdc.eu/&lt;/a&gt;) is a
consortium between groups involved in the generation, evaluation, and
use of atomic and molecular data, funded by the European Union. VAMDC
aims to build a reliable, open, flexible and interoperable e-science
interface to existing atomic and molecular data. The project will cover
establishing the core consortium, the development and deployment of
the infrastructure and the development of interfaces to the existing
atomic and molecular databases. This paper describes the organisation
of the project and the achievements at the end of its second year.

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Title: M-dwarf metallicities. A high-resolution spectroscopic study
in the near infrared
Authors: Önehag, A.; Heiter, U.; Gustafsson, B.; Piskunov, N.; Plez,
B.; Reiners, A.
2012A&A...542A..33O Altcode: 2011arXiv1112.0141O
Context. The relatively wide spread in the derived metallicities
([Fe/H]) of M dwarfs shows that various approaches have not yet
converged to consistency. The presence of strong molecular features
and incomplete line lists for the corresponding molecules have made
determining the metallicity of M dwarfs difficult. Furthermore, the
faint M dwarfs require long exposure times for the signal-to-noise
ratio needed for a detailed spectroscopic abundance analysis. 
Aims: We present a high-resolution (R ~ 50 000) spectroscopic study
of a sample of eight single M dwarfs and three wide-binary systems
observed in the infrared J band. Methods: The absence of large
molecular contributions allows for a precise continuum placement. We
derived metallicities based on the best fit of synthetic spectra to
the observed spectra. To verify the accuracy of the applied atmospheric
models and test our synthetic spectrum approach, three binary systems
with a K-dwarf primary and an M-dwarf companion were observed and
analysed along with the single M dwarfs. Results: We obtain
good agreement between the metallicities derived for the primaries and
secondaries of our test binaries, thereby confirming the reliability
of our method of analysing M dwarfs. Our metallicities agree well
with some earlier determinations, and deviate from others. 
Conclusions: We conclude that spectroscopic abundance analysis in the J
band is a reliable method for establishing the metallicity scale for M
dwarfs. We recommend its application to a larger sample covering lower,
as well as higher, metallicities. Further prospects for the method
include abundance determinations for individual elements. Based
on data obtained at ESO-VLT, Paranal Observatory, Chile, Program ID
082.D-0838(A) and 084.D-1042(A).Table 2 is available in electronic form
at <A href="http://www.aanda.org">http://www.aanda.org</A>Electronic
version of the spectra is only available at CDS via
anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/542/A33">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/542/A33</A>

---------------------------------------------------------
Title: VizieR Online Data Catalog: 3 M dwarfs near-infrared spectra
(Onehag+, 2012)
Authors: Onehag, A.; Heiter, U.; Gustafsson, B.; Piskunov, N.; Plez,
B.; Reiners, A.
2012yCat..35420033O Altcode: 2012yCat..35429033O
The observations were carried out in service mode with the infrared
spectrometer CRIRES at ESO-VLT. In total 14 targets were observed
during periods 82 (1st of October 2008 to 31st of March 2009) and 84
(1st of October 2009 to 31st of March 2010). (4 data files).

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Title: HARPS spectropolarimetry of classical T Tauri stars
Authors: Johns-Krull, C. M.; Valenti, J. A.; Jeffers, S. V.; Piskunov,
N. E.; Kochukhov, O.; Keller, C.; Snik, F.; Rodenhuis, M.; Makaganiuk,
V.; Stempels, H.
2012AIPC.1429...43J Altcode:
We present high spectral resolution Stokes V polarimetery of the
Classical T Tauri stars (CTTSs) GQ Lup and TW Hya obtained with
the polarimetric upgrade to the HARPS spectrometer on the ESO 3.6 m
telescope. We present data on both photospheric lines and emission
lines, concentrating our discussion on the polarization properties
of the He I emission lines at 5876 A and 6678 A. The He I lines
in both these CTTS contain both narrow emission cores, believed to
come from near the accretion shock region on these stars, and broad
emission components which may come from either a wind or the large
scale magnetospheric accretion flow. We detect strong polarization in
the narrow component of both the He I emission lines in both stars. We
observe a maximum implied field strength of 5.8 +/- 0.3 kG in the 5876
A˚ line of GQ Lup, the highest field strength measured to date in
this line for a CTTS. We find field strengths in the two He I lines
that are consistent with each other, unlike what has been reported in
the literature on at least one star. We do not detect any polarization
in the broad component of the He I lines on these stars, strengthening
the conclusion that they form over a substantially different volume
relative the formation region of the narrow component of the He I lines.

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Title: Division Iv: Stars
Authors: Corbally, Christopher; D'Antona, Francesca; Spite, Monique;
Asplund, Martin; Charbonnel, Corinne; Docobo, Jose Angel; Gray,
Richard O.; Piskunov, Nikolai E.
2012IAUTA..28..147C Altcode:
This Division IV was started on a trial basis at the General Assembly
in The Hague 1994 and was formally accepted at the Kyoto General
Assembly in 1997. Its broad coverage of “Stars” is reflected in
its relatively large number of Commissions and so of members (1266 in
late 2011). Its kindred Division V, “Variable Stars”, has the same
history of its beginning. The thinking at the time was to achieve
some kind of balance between the number of members in each of the 12
Divisions. Amid the current discussion of reorganizing the number of
Divisions into a more compact form it seems advisable to make this
numerical balance less of an issue than the rationalization of the
scientific coverage of each Division, so providing more effective
interaction within a particular field of astronomy. After all, every
star is variable to a certain degree and such variability is becoming
an ever more powerful tool to understand the characteristics of every
kind of normal and peculiar star. So we may expect, after hearing the
reactions of members, that in the restructuring a single Division will
result from the current Divisions IV and V.

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Title: Divisions Iv-V / Working Group ap &amp; Related Stars
Authors: Mathys, Gautier; Cunha, Margarida; Dworetsky, Michael;
Kochukhov, Oleg; Kupka, Friedrich; LeBlanc, Francis; Monier, Richard;
Paunzen, Ernst; Pintado, Olga; Piskunov, Nikolai; Ziznovsky, Jozef
2012IAUTA..28..203M Altcode:
The purpose of the Working Group on Ap and Related Stars (ApWG) is
to promote and facilitate research about stars in the spectral type
range from B to early F that exhibit surface chemical peculiarities
and related phenomena. This is a very active field of research, in
which a wide variety of new developments have taken place since 2009,
as illustrated by the following selected highlights.

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Title: Magnetism, chemical spots, and stratification in the HgMn
star ϕ Phoenicis
Authors: Makaganiuk, V.; Kochukhov, O.; Piskunov, N.; Jeffers, S. V.;
Johns-Krull, C. M.; Keller, C. U.; Rodenhuis, M.; Snik, F.; Stempels,
H. C.; Valenti, J. A.
2012A&A...539A.142M Altcode: 2011arXiv1111.6065M
Context. Mercury-manganese (HgMn) stars have been considered as
non-magnetic and non-variable chemically peculiar (CP) stars for a
long time. However, recent discoveries of the variability in spectral
line profiles have suggested an inhomogeneous surface distribution
of chemical elements in some HgMn stars. From the studies of other
CP stars it is known that magnetic field plays a key role in the
formation of surface spots. All attempts to find magnetic fields in
HgMn stars have yielded negative results. Aims: In this study,
we investigate the possible presence of a magnetic field in ϕ Phe
(HD 11753) and reconstruct surface distribution of chemical elements
that show variability in spectral lines. We also test a hypothesis
that a magnetic field is concentrated in chemical spots and look into
the possibility that some chemical elements are stratified with depth
in the stellar atmosphere. Methods: Our analysis is based on
high-quality spectropolarimetric time-series observations, covering
a full rotational period of the star. Spectra were obtained with the
HARPSpol at the ESO 3.6-m telescope. To increase the sensitivity of
the magnetic field search, we employed the least-squares deconvolution
(LSD) technique. Using Doppler imaging code INVERS10, we reconstructed
surface chemical distributions by utilising information from
multiple spectral lines. The vertical stratification of chemical
elements was calculated with the DDAFit program. Results:
Combining information from all suitable spectral lines, we set an
upper limit of 4 G on the mean longitudinal magnetic field. For
chemical spots, an upper limit on the longitudinal field varies
between 8 and 15 G. We confirmed the variability of Y, Sr, and Ti
and detected variability in Cr lines. Stratification analysis showed
that Y and Ti are not concentrated in the uppermost atmospheric
layers. Conclusions: Our spectropolarimetric observations
rule out the presence of a strong, globally-organised magnetic field
in ϕ Phe. This implies an alternative mechanism of spot formation,
which could be related to a non-equilibrium atomic diffusion. However,
the typical time scales of the variation in stratification predicted
by the recent time-dependent diffusion models exceed significantly
the spot evolution time-scale reported for ϕ Phe. Based on
observations collected at the European Southern Observatory, Chile
(ESO programme 084.D-0338). Figures 9-12 are available in electronic
form at <A href="http://www.aanda.org">http://www.aanda.org</A>

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Title: SME: Spectroscopy Made Easy
Authors: Valenti, J. A.; Piskunov, N.
2012ascl.soft02013V Altcode:
Spectroscopy Made Easy (SME) is IDL software and a compiled external
library that fits an observed high-resolution stellar spectrum with a
synthetic spectrum to determine stellar parameters. The SME external
library is available for Mac, Linux, and Windows systems. Atomic and
molecular line data formatted for SME may be obtained from VALD. SME can
solve for empirical log(gf) and damping parameters, using an observed
spectrum of a star (usually the Sun) as a constraint.

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Title: Doppler images of II Pegasi for 2004-2010
Authors: Hackman, T.; Mantere, M. J.; Lindborg, M.; Ilyin, I.;
Kochukhov, O.; Piskunov, N.; Tuominen, I.
2012A&A...538A.126H Altcode: 2011arXiv1106.6237H
 Aims: We study the spot activity of <ASTROBJ>II Peg</ASTROBJ>
during the years 2004-2010 to determine long- and short-term changes in
the magnetic activity. In a previous study, we detected a persistent
active longitude, as well as major changes in the spot configuration
occurring on a timescale of shorter than a year. The main objective
of this study is to determine whether the same phenomena persist in
the star during these six years of spectroscopic monitoring. 
Methods: The observations were collected with the high-resolution
SOFIN spectrograph at the Nordic Optical Telescope. The temperature
maps were calculated using a Doppler imaging code based on Tikhonov
regularization. Results: We present 12 new temperature maps that
show spots distributed mainly over high and intermediate latitudes. In
each image, 1-3 main active regions can be identified. The activity
level of the star is clearly lower than during our previous study
for the years 1994-2002. In contrast to the previous observations,
we detect no clear drift of the active regions with respect to the
rotation of the star. Conclusions: Having shown a systematic
longitudinal drift of the spot-generating mechanism during 1994-2002,
the star has clearly switched to a low-activity state for 2004-2010,
during which the spot locations appear more random over phase space. It
could be that the star is near to a minimum of its activity cycle. Based on observations made with the Nordic Optical Telescope, operated
on the island of La Palma jointly by Denmark, Finland, Iceland, Norway,
and Sweden, in the Spanish Observatorio del Roque de los Muchachos of
the Instituto de Astrofisica de Canarias.

---------------------------------------------------------
Title: M2K. II. A Triple-planet System Orbiting HIP 57274
Authors: Fischer, Debra A.; Gaidos, Eric; Howard, Andrew W.; Giguere,
Matthew J.; Johnson, John A.; Marcy, Geoffrey W.; Wright, Jason T.;
Valenti, Jeff A.; Piskunov, Nikolai; Clubb, Kelsey I.; Isaacson,
Howard; Apps, Kevin; Lepine, Sebastien; Mann, Andrew; Moriarty, John;
Brewer, John; Spronck, Julien F. P.; Schwab, Christian; Szymkowiak,
Andrew
2012ApJ...745...21F Altcode: 2011arXiv1109.2926F
Doppler observations from Keck Observatory have revealed a triple-planet
system orbiting the nearby K4V star, HIP 57274. The inner planet,
HIP 57274b, is a super-Earth with Msin i = 11.6 M ⊕
(0.036 M Jup), an orbital period of 8.135 ± 0.004 days,
and slightly eccentric orbit e = 0.19 ± 0.1. We calculate a transit
probability of 6.5% for the inner planet. The second planet has Msin i =
0.4 M Jup with an orbital period of 32.0 ± 0.02 days in a
nearly circular orbit (e = 0.05 ± 0.03). The third planet has Msin i
= 0.53 M Jup with an orbital period of 432 ± 8 days (1.18
years) and an eccentricity e = 0.23 ± 0.03. This discovery adds to the
number of super-Earth mass planets with M sin i &lt; 12 M ⊕
that have been detected with Doppler surveys. We find that 56% ± 18%
of super-Earths are members of multi-planet systems. This is certainly
a lower limit because of observational detectability limits, yet
significantly higher than the fraction of Jupiter mass exoplanets, 20%
± 8%, that are members of Doppler-detected, multi-planet systems. Based on observations obtained at the Keck Observatory, which is
operated by the University of California.

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Title: Multi-element Doppler imaging of the CP2 star HD 3980
Authors: Nesvacil, N.; Lüftinger, T.; Shulyak, D.; Obbrugger, M.;
Weiss, W.; Drake, N. A.; Hubrig, S.; Ryabchikova, T.; Kochukhov, O.;
Piskunov, N.; Polosukhina, N.
2012A&A...537A.151N Altcode:
Context. In atmospheres of magnetic main-sequence stars, the diffusion
of chemical elements leads to a number of observed anomalies, such as
abundance spots across the stellar surface. Aims: The aim of
this study was to derive a detailed picture of the surface abundance
distribution of the magnetic chemically peculiar star HD 3980. Methods: Based on high-resolution, phase-resolved spectroscopic
observations of the magnetic A-type star HD 3980, the inhomogeneous
surface distribution of 13 chemical elements (Li, O, Si, Ca, Cr, Mn,
Fe, La, Ce, Pr, Nd, Eu, and Gd) has been reconstructed. The INVERS12
code was used to invert the rotational variability in line profiles to
elemental surface distributions. Results: Assuming a centered,
dominantly dipolar magnetic field configuration, we find that Li, O,
Mg, Pr, and Nd are mainly concentrated in the area of the magnetic
poles and depleted in the regions around the magnetic equator. The
high abundance spots of Si, La, Ce, Eu, and Gd are located between
the magnetic poles and the magnetic equator. Except for La, which
is clearly depleted in the area of the magnetic poles, no obvious
correlation with the magnetic field has been found for these elements
otherwise. Ca, Cr, and Fe appear enhanced along the rotational equator
and the area around the magnetic poles. The intersection between the
magnetic and the rotational equator constitutes an exception, especially
for Ca and Cr, which are depleted in that region. Conclusions:
No obvious correlation between the theoretically predicted abundance
patterns and those determined in this study could be found. This can
be attributed to a lack of up-to-date theoretical models, especially
for rare earth elements. Table 1 is available in electronic form
at <A href="http://www.aanda.org">http://www.aanda.org</A>

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Title: New Insights into Stellar Magnetism from the Spectropolarimetry
in All Four Stokes Parameters
Authors: Kochukhov, O.; Snik, F.; Piskunov, N.; Jeffers, S. V.;
Keller, C. U.; Makaganiuk, V.; Valenti, J. A.; Johns-Krull, C. M.;
Rodenhuis, M.; Stempels, H. C.
2011ASPC..448..245K Altcode: 2011csss...16..245K
Development of high-resolution spectropolarimetry has stimulated a
major progress in our understanding of the magnetism and activity of
late-type stars. During the last decade magnetic fields were discovered
and mapped for various types of active stars using spectropolarimetric
methods. However, these observations and modeling attempts are
inherently incomplete since they are based on the interpretation of the
stellar circular polarization alone. Taking advantage of the recently
commissioned HARPS polarimeter, we obtained the first systematic
observations of cool active stars in all four Stokes parameters. Here we
report detection of the magnetically induced linear polarization in the
RS CVn binary HR 1099 and phase-resolved full Stokes vector observations
of varepsilon Eri. For the latter star we measured the field strength
with the precision of ∼0.1 G over a complete rotation cycle and
reconstructed the global field topology with the help of magnetic
Doppler imaging. Our observations of the inactive solar-like star α
Cen A indicate the absence of the global field stronger than 0.2 G.

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Title: Rotation, magnetism and metallicity of M dwarf systems
Authors: Shulyak, D.; Seifahrt, A.; Reiners, A.; Kochukhov, O.;
Piskunov, N.
2011MNRAS.418.2548S Altcode: 2011MNRAS.tmp.1579S; 2011arXiv1108.3465S
Close M dwarf binaries and higher multiples allow the investigation
of rotational evolution and mean magnetic flux unbiased from scatter
in inclination angle and age since the orientation of the spin axis of
the components is most likely parallel and the individual systems are
coeval. Systems composed of an early-type (M0.0-M4.0) and a late-type
(M4.0-M8.0) component offer the possibility to study differences
in rotation and magnetism between partially and fully convective
stars. We have selected 10 of the closest dM systems to determine the
rotation velocities and the mean magnetic field strengths based on
spectroscopic analysis of FeH lines of Wing-Ford transitions at 1 μm
observed with Very Large Telescope/CRIRES. We also studied the quality
of our spectroscopic model regarding atmospheric parameters including
metallicity. A modified version of the Molecular Zeeman Library
(MZL) was used to compute Landég-factors for FeH lines. Magnetic
spectral synthesis was performed with the SYNMAST code. We confirmed
previously reported findings that less massive M dwarfs are braked less
effectively than objects of earlier types. Strong surface magnetic
fields were detected in primaries of four systems (GJ 852, GJ 234,
LP 717-36 and GJ 3322), and in the secondary of the triple system GJ
852. We also confirm strong 2-kG magnetic field in the primary of the
triple system GJ 2005. No fields could be accurately determined in
rapidly rotating stars with υ sin i &gt; 10 km s-1. For
slowly and moderately rotating stars, we find the surface magnetic
field strength to increase with the rotational velocity υ sin i which
is consistent with other results from studying field stars. Based on
observations made with European Southern Observatory (ESO) Telescopes
at the Paranal Observatories under programme ID 81.D-0189.

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Title: Magnetic Fields in M-dwarfs: Quantitative Results from Detailed
Spectral Synthesis in FeH Lines
Authors: Shulyak, D.; Reiners, A.; Wende, S.; Kochukhov, O.; Piskunov,
N.; Seifahrt, A.
2011ASPC..448.1263S Altcode: 2011csss...16.1263S; 2010arXiv1012.1435S
Strong surface magnetic fields are ubiquitously found in M-dwarfs with
mean intensities on the order of few thousand Gauss -- three orders of
magnitude higher than the mean surface magnetic field of the Sun. These
fields and their interaction with photospheric convection are the main
source of stellar activity, which is of big interest to study links
between parent stars and their planets. Moreover, the understanding of
stellar magnetism, as well as the role of different dynamo-actions
in particular, is impossible without explaining magnetic fields
in M-dwarfs. Measuring magnetic field intensities and geometries
in such cool objects, however, is strongly limited to our ability
to simulate the Zeeman effect in molecular lines. In this work, we
present quantitative results of modelling and analysis of the magnetic
fields in selected M-dwarfs in FeH Wing-Ford lines and strong atomic
lines. Some particular FeH lines are found to be the excellent probes
of the magnetic field.

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Title: Spot activity of II Peg
Authors: Hackman, T.; Mantere, M. J.; Jetsu, L.; Ilyin, I.;
Kajatkari, P.; Kochukhov, O.; Lehtinen, J.; Lindborg, M.; Piskunov,
N.; Tuominen, I.
2011AN....332..859H Altcode:
We have studied the long-term spot activity of the RS CVn star II Peg
by means of Doppler imaging based on spectroscopy and time series
analysis of photometry. We present 28 Doppler imaging temperature
maps spanning the years 1994-2010, of which 14 were calculated for
the present study. The longitudinal spot distribution, derived from
the surface temperature maps, is compared with epochs of the light
curve minima, derived from photometric observations. We detect a
longitudinal drift in the major spot structure during 1995-2003. After
this there is a clear decrease in the activity level and no clear
drift can be seen. We conclude that the variations could be caused
by a cyclic behaviour of the underlying magnetic dynamo. Based
on observations made with the Nordic Optical Telescope, operated on
the island of La Palma jointly by Denmark, Finland, Iceland, Norway,
and Sweden, in the Spanish Observatorio del Roque de los Muchachos of
the Instituto de Astrofisica de Canarias.

---------------------------------------------------------
Title: No magnetic field in the spotted HgMn star μ Leporis
Authors: Kochukhov, O.; Makaganiuk, V.; Piskunov, N.; Jeffers, S. V.;
Johns-Krull, C. M.; Keller, C. U.; Rodenhuis, M.; Snik, F.; Stempels,
H. C.; Valenti, J. A.
2011A&A...534L..13K Altcode: 2011arXiv1110.0829K
Context. Chemically peculiar stars of the mercury-manganese (HgMn)
type represent a new class of spotted late-B stars, in which evolving
surface chemical inhomogeneities are apparently unrelated to the
presence of strong magnetic fields but are produced by some hitherto
unknown astrophysical mechanism. Aims: The goal of this study
is to perform a detailed line profile variability analysis and carry
out a sensitive magnetic field search for one of the brightest HgMn
stars - μ Lep. Methods: We acquired a set of very high-quality
intensity and polarization spectra of μ Lep with the HARPSpol
polarimeter. These data were analyzed with the multiline technique
of least-squares deconvolution in order to extract information on
the magnetic field and line profile variability. Results:
Our spectra show very weak but definite variability in the lines
of Sc, all Fe-peak elements represented in the spectrum of μ Lep,
as well as Y, Sr, and Hg. Variability might also be present in the
lines of Si and Mg. Anomalous profile shapes of Ti ii and Y ii lines
suggest a dominant axisymmetric distribution of these elements. At
the same time, we found no evidence of the magnetic field in μ Lep,
with the 3σ upper limit of only 3 G for the mean longitudinal magnetic
field. This is the most stringent upper limit on the possible magnetic
field derived for a spotted HgMn star. Conclusions: The very
weak variability detected for many elements in the spectrum μ Lep
suggests that low-contrast chemical inhomogeneities may be common in
HgMn stars and that they have not been recognized until now due to the
limited precision of previous spectroscopic observations and a lack
of time-series data. The null result of the magnetic field search
reinforces the conclusion that formation of chemical spots in HgMn
stars is not magnetically driven. Based on observations collected
at the European Southern Observatory, Chile (ESO programs 084.D-0338,
086.D-0240).

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Title: Analyzing low signal-to-noise FUSE spectra. Confirmation of
Lyman continuum escape from Haro 11
Authors: Leitet, E.; Bergvall, N.; Piskunov, N.; Andersson, B. -G.
2011A&A...532A.107L Altcode: 2011arXiv1106.1178L
Context. Galaxies are believed to be the main providers of Lyman
continuum (LyC) photons during the early phases of the cosmic
reionization. Little is known however, when it comes to escape fractions
and the mechanisms behind the leakage. To learn more, one may look at
local objects, but so far only one low-z galaxy has shown any signs of
emitting LyC radiation. With data from the Far Ultraviolet Spectroscopic
Explorer (FUSE), we previously found an absolute escape fraction of
ionizing photons (fesc) of 4-10% for the blue compact galaxy
<ASTROBJ>Haro 11</ASTROBJ>. However, using a revised version of the
reduction pipeline on the same data set, Grimes and collaborators were
unable to confirm this and derived an upper limit of fesc ≲
2% . Aims: We attempt to determine whether Haro 11 is emitting
ionizing radiation to a significant level or not. We also investigate
the performance of the reduction pipeline for faint targets such as Haro
11, and introduce a new approach to the background subtraction. 
Methods: The final version of the reduction pipeline, CalFUSE v3.2,
was applied to the same Haro 11 data set as the two previous authors
used. At these faint flux levels, both FUSE and CalFUSE are pushed
to their limits, and a detailed analysis was undertaken to monitor
the performance of the pipeline. We show that non-simultaneous
background estimates are insuffient when working with data of low
signal-to-noise ratio (S/N), and a new background model was developed
based on a direct fit to the detector response. Results: We
find that one has to be very careful when using CalFUSE v3.2 on low
S/N data, and especially when dealing with sources where signal might
originate from off-center regions. Applying the new background fit,
a significant signal is detected in the LyC in both detector segments
covering these wavelengths. Thus, the leakage is confirmed with a flux
density of f900 = 4.0 × 10-15 erg s-1
cm-2 Å-1 (S/N = 4.6), measured on the airglow
free regions in the LyC for the night-only data. This corresponds
to an absolute escape fraction of ionizing photons from Haro 11 of
fesc = 3.3 ± 0.7%. We confirm these results by investigating
the two-dimensional data, the count rates, and the residual flux in
C ii λ1036 Å. Appendix A is available in electronic form at
<A href="http://www.aanda.org">http://www.aanda.org</A>

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Title: Starspot variability and evolution from modeling Kepler
photometry of active late-type stars
Authors: Brown, Alexander; Korhonen, Heidi; Berdyugina, Svetlana;
Tofany, Barton; Ayres, Thomas R.; Kowalski, Adam; Hawley, Suzanne;
Harper, Graham; Piskunov, Nikolai
2011IAUS..273...78B Altcode:
The Kepler satellite provides a unique opportunity to study the detailed
optical photometric variability of late-type stars with unprecedentedly
long (several year) continuous monitoring and sensitivity to very
small-scale variations. We are studying a sample of over two hundred
cool (mid-A - late-K spectral type) stars using Kepler long-cadence
(30 minute sampling) observations. These stars show a remarkable
range of photometric variability, but in this paper we concentrate on
rotational modulation due to starspots and flaring. Modulation at the
0.1% level is readily discernable. We highlight the rapid timescales
of starspot evolution seen on solar-like stars with rotational periods
between 2 and 7 days.

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Title: VAMDC: The Virtual Atomic and Molecular Data Center
Authors: Walton, N. A.; Dubernet, M. L.; Mason, N. J.; Piskunov, N.;
Rixon, G. T.; Vamdc Consortium
2011ASPC..442...89W Altcode: 2011adass..20...89W
The Virtual Atomic and Molecular Data Center (VAMDC) is a European
Union funded collaboration between groups involved in the generation,
evaluation, and use of atomic and molecular data. VAMDC aims to
build a secure, documented, flexible and interoperable e-science
environment-based interface to existing atomic and molecular data. The
project will cover establishing the core consortium, the development
and deployment of the infrastructure and the development of interfaces
to the existing atomic and molecular databases. This paper describes
the organization, its objectives and introduces the VAMDC level one
service release.

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Title: The search for magnetic fields in mercury-manganese stars
Authors: Makaganiuk, Vitalii; Kochukhov, Oleg; Piskunov, Nikolai;
Jeffers, Sandra V.; Johns-Krull, Christopher M.; Keller, Christoph
U.; Rodenhuis, Michiel; Snik, Frans; Stempels, Henricus C.; Valenti,
Jeff A.
2011IAUS..272..202M Altcode:
Mercury-manganese (HgMn) stars were considered to be non-magnetic,
showing no evidence of surface spots. However, recent investigations
revealed that some stars in this class possess an inhomogeneous
distribution of chemical elements on their surfaces. According to
our current understanding, the most probable mechanism of spot
formation involves magnetic fields. Taking the advantage of a
newly-built polarimeter attached to the HARPS spectrometer at the
ESO 3.6m-telescope, we performed a high-precision spectropolarimetric
survey of a large group of HgMn stars. The main purpose of this study
was to find out how typical it is for HgMn stars to have weak magnetic
fields. We report no magnetic field detection for any of the studied
objects, with a typical precision of the longitudinal field measurements
of 10 G and down to 1 Gauss for some of the stars. We conclude that HgMn
stars lack large-scale magnetic fields typical of spotted magnetic Ap
stars and probably lack any fields capable of creating and sustaining
chemical spots. Our study confirms that alongside the magnetically
altered atomic diffusion, there must be other structure formation
mechanism operating in the atmospheres of late-B main sequence stars.

---------------------------------------------------------
Title: Chemical spots in the absence of magnetic field in the binary
HgMn star 66 Eridani
Authors: Makaganiuk, V.; Kochukhov, O.; Piskunov, N.; Jeffers, S. V.;
Johns-Krull, C. M.; Keller, C. U.; Rodenhuis, M.; Snik, F.; Stempels,
H. C.; Valenti, J. A.
2011A&A...529A.160M Altcode: 2011arXiv1102.4661M
Context. According to our current understanding, a subclass of the
upper main-sequence chemically peculiar stars, called mercury-manganese
(HgMn), is non-magnetic. Nevertheless, chemical inhomogeneities were
recently discovered on their surfaces. At the same time, no global
magnetic fields stronger than 1-100 G are detected by systematic
studies. Aims: The goals of our study are to search for a
magnetic field in the HgMn binary system 66 Eri and to investigate
chemical spots on the stellar surfaces of both components. 
Methods: Our analysis is based on high-quality spectropolarimetric
time-series observations obtained during 10 consecutive nights with
the HARPSpol instrument at the ESO 3.6-m telescope. To increase the
sensitivity of the magnetic field search we employed a least-squares
deconvolution (LSD). We used spectral disentangling to measure radial
velocities and study the line profile variability. Chemical spot
geometry was reconstructed using multi-line Doppler imaging. 
Results: We report a non-detection of magnetic field in 66 Eri, with
error bars 10-24 G for the longitudinal field. Circular polarization
profiles also do not indicate any signatures of complex surface
magnetic fields. For a simple dipolar field configuration we estimated
an upper limit of the polar field strength to be 60-70 G. For the
HgMn component we found variability in spectral lines of Ti, Ba,
Y, and Sr with the rotational period equal to the orbital one. The
surface maps of these elements reconstructed with the Doppler imaging
technique show a relative underabundance on the hemisphere facing the
secondary component. The contrast of chemical inhomogeneities ranges
from 0.4 for Ti to 0.8 for Ba. Based on observations collected
at the European Southern Observatory, Chile (ESO program 084.D-0338).

---------------------------------------------------------
Title: First Detection of Linear Polarization in the Line Profiles
of Active Cool Stars
Authors: Kochukhov, O.; Makaganiuk, V.; Piskunov, N.; Snik, F.;
Jeffers, S. V.; Johns-Krull, C. M.; Keller, C. U.; Rodenhuis, M.;
Valenti, J. A.
2011ApJ...732L..19K Altcode: 2011arXiv1103.6028K
The application of high-resolution spectropolarimetry has led to major
progress in understanding the magnetism and activity of late-type
stars. During the last decade, magnetic fields have been discovered and
mapped for many types of active cool stars using spectropolarimetric
data. However, these observations and modeling attempts are
fundamentally incomplete since they are based on the interpretation of
the circular polarization alone. Taking advantage of the newly built
HARPS polarimeter, we have obtained the first systematic observations
of several cool active stars in all four Stokes parameters. Here we
report the detection of magnetically induced linear polarization for
the primary component of the very active RS CVn binary HR 1099 and
for the moderately active K dwarf ɛ Eri. For both stars the amplitude
of linear polarization signatures is measured to be ~10-4
of the unpolarized continuum, which is approximately a factor of 10
lower than for circular polarization. This is the first detection of
the linear polarization in line profiles of cool active stars. Our
observations of the inactive solar-like star α Cen A show neither
circular nor linear polarization above the level of ~10-5,
indicating the absence of a net longitudinal magnetic field stronger
than 0.2 G. Based on observations obtained at the European Southern
Observatory (ESO programs 083.D-1000(A) and 084.D-0338(A)).

---------------------------------------------------------
Title: Kepler Observations of Starspot Evolution, Differential
Rotation, and Flares on Late-Type Stars
Authors: Brown, Alexander; Korhonen, H.; Berdyugina, S.; Walkowicz,
L.; Kowalski, A.; Hawley, S.; Neff, J.; Ramsey, L.; Redman, S.; Saar,
S.; Furesz, G.; Piskunov, N.; Harper, G.; Ayres, T.; Tofany, B.
2011AAS...21820502B Altcode: 2011BAAS..43G20502B
The Kepler satellite is providing spectacular optical photometric
light-curves of unprecedented precision and duration that
routinely allow detailed studies of stellar magnetic activity on
late-type stars that were difficult, if not impossible, to attempt
previously. Rotational modulation due to starspots is commonly seen
in the Kepler light-curves of late-type stars, allowing detailed
study of the surface distribution of their photospheric magnetic
activity. Kepler is providing multi-year duration light-curves that
allow us to investigate how activity phenomena -- such as the growth,
migration, and decay of starspots, differential rotation, activity
cycles, and flaring -- operate on single and binary stars with a
wide range of mass and convection zone depth. We present the
first results from detailed starspot modeling using newly-developed
light-curve inversion codes for a range of GALEX-selected stars with
typical rotation periods of a few days, that we have observed as part of
our 200 target Kepler Cycle 1/2 Guest Observer programs. The physical
properties of the stars have been measured using high resolution
optical spectroscopy, which allows the Kepler results to be placed
within the existing framework of knowledge regarding stellar magnetic
activity. These results demonstrate the powerful diagnostic capability
provided by tracking starspot evolution essentially continuously for
more than 16 months. The starspots are clearly sampling the stellar
rotation rate at different latitudes, enabling us to measure the
differential rotation and starspot lifetimes. As would be expected,
stars with few day rotation show frequent flaring that is easily seen
as "white-light" flares in Kepler light-curves. We compare the observed
flare rates and occurrence with the starspot properties. This work
contains results obtained using the NASA Kepler satellite and from the
Apache Point Observatory, the MMT (using NOAO community access time),
and the Hobby-Eberly Telescope. Funding is provided by NASA Kepler
grants NNX10AC51G and NNX11AC79G.

---------------------------------------------------------
Title: The HARPS Polarimeter
Authors: Snik, F.; Kochukhov, O.; Piskunov, N.; Rodenhuis, M.; Jeffers,
S.; Keller, C.; Dolgopolov, A.; Stempels, E.; Makaganiuk, V.; Valenti,
J.; Johns-Krull, C.
2011ASPC..437..237S Altcode: 2010arXiv1010.0397S
We recently commissioned the polarimetric upgrade of the HARPS
spectrograph at ESO's 3.6-m telescope at La Silla, Chile. The HARPS
polarimeter is capable of full Stokes spectropolarimetry with large
sensitivity and accuracy, taking advantage of the large spectral
resolution and stability of HARPS. In this paper we present the
instrument design and its polarimetric performance. The first HARPSpol
observations show that it can attain a polarimetric sensitivity
of ∼10-5 (after addition of many lines) and that no
significant instrumental polarization effects are present.

---------------------------------------------------------
Title: The Exoplanet Orbit Database
Authors: Wright, J. T.; Fakhouri, O.; Marcy, G. W.; Han, E.; Feng,
Y.; Johnson, John Asher; Howard, A. W.; Fischer, D. A.; Valenti,
J. A.; Anderson, J.; Piskunov, N.
2011PASP..123..412W Altcode: 2010arXiv1012.5676W
We present a database of well-determined orbital parameters of
exoplanets, and their host stars’ properties. This database comprises
spectroscopic orbital elements measured for 427 planets orbiting 363
stars from radial velocity and transit measurements as reported in
the literature. We have also compiled fundamental transit parameters,
stellar parameters, and the method used for the planets discovery. This
Exoplanet Orbit Database includes all planets with robust, well measured
orbital parameters reported in peer-reviewed articles. The database is
available in a searchable, filterable, and sortable form online through
the Exoplanets Data Explorer table, and the data can be plotted and
explored through the Exoplanet Data Explorer plotter. We use the Data
Explorer to generate publication-ready plots, giving three examples
of the signatures of exoplanet migration and dynamical evolution:
We illustrate the character of the apparent correlation between mass
and period in exoplanet orbits, the different selection biases between
radial velocity and transit surveys, and that the multiplanet systems
show a distinct semimajor-axis distribution from apparently singleton
systems.

---------------------------------------------------------
Title: The NASA-UC Eta-Earth Program. III. A Super-Earth Orbiting
HD 97658 and a Neptune-mass Planet Orbiting Gl 785
Authors: Howard, Andrew W.; Johnson, John Asher; Marcy, Geoffrey W.;
Fischer, Debra A.; Wright, Jason T.; Henry, Gregory W.; Isaacson,
Howard; Valenti, Jeff A.; Anderson, Jay; Piskunov, Nikolai E.
2011ApJ...730...10H Altcode: 2010arXiv1011.0414H
We report the discovery of planets orbiting two bright, nearby early
K dwarf stars, HD 97658 and Gl 785. These planets were detected by
Keplerian modeling of radial velocities measured with Keck-HIRES for
the NASA-UC Eta-Earth Survey. HD 97658 b is a close-in super-Earth
with minimum mass Msin i = 8.2 ± 1.2 M ⊕, orbital
period P = 9.494 ± 0.005 days, and an orbit that is consistent with
circular. Gl 785 b is a Neptune-mass planet with Msin i = 21.6 ± 2.0
M ⊕, P = 74.39 ± 0.12 days, and orbital eccentricity e =
0.30 ± 0.09. Photometric observations with the T12 0.8 m automatic
photometric telescope at Fairborn Observatory show that HD 97658 is
photometrically constant at the radial velocity period to 0.09 mmag,
supporting the existence of the planet. Based on observations
obtained at the W. M. Keck Observatory, which is operated jointly
by the University of California and the California Institute of
Technology. Keck time has been granted by both NASA and the University
of California.

---------------------------------------------------------
Title: HARPSpol — The New Polarimetric Mode for HARPS
Authors: Piskunov, N.; Snik, F.; Dolgopolov, A.; Kochukhov, O.;
Rodenhuis, M.; Valenti, J.; Jeffers, S.; Makaganiuk, V.; Johns-Krull,
C.; Stempels, E.; Keller, C.
2011Msngr.143....7P Altcode:
The HARPS spectrograph can now perform a full polarisation analysis
of spectra. It has been equipped with a polarimetric unit, HARPSpol,
which was jointly designed and produced by Uppsala, Utrecht and Rice
Universities and by the STScI. Here we present the new instrument,
demonstrate its polarisation capabilities and show the first scientific
results.

---------------------------------------------------------
Title: Doppler images of the RS CVn binary II Pegasi during the
years 1994-2002
Authors: Lindborg, M.; Korpi, M. J.; Hackman, T.; Tuominen, I.; Ilyin,
I.; Piskunov, N.
2011A&A...526A..44L Altcode:
 Aims: We publish 16 Doppler imaging temperature maps for the
years 1994-2002 of the active RS CVn star II Peg. The six maps from
1999-2002 are based on previously unpublished observations. Through
Doppler imaging we want to study the spot evolution of the star and
in particular compare this with previous results showing a cyclic
spot behaviour and persistent, active longitudes. Methods:
The observations were collected with the SOFIN spectrograph at the
Nordic Optical Telescope. The temperature maps were calculated using a
Doppler imaging code based on Tikhonov regularization. Results:
During 1994-2001, our results show a consistent trend in the derived
longitudes of the principal and secondary temperature minima over
time such that the magnetic structure appears to rotate somewhat more
rapidly than the orbital period of this close binary. A sudden phase
jump in the active region occurred between the observing seasons of
2001 and 2002. No clear trend over time is detected in the derived
latitudes of the spots, indicating that the systematic motion could
be related to the drift of the spot-generating mechanism rather than
to differential rotation. The derived temperature maps are quite
similar to the ones obtained earlier with different methods and the
main differences occur in the spot latitudes and relative strength of
the spot structures. Conclusions: We observe both longitude and
latitude shifts in the spot activity of II Peg. However, our results
are not consistent with the periodic behaviour presented in previous
studies. Full Table 1 is only available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/526/A44">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/526/A44</A>

---------------------------------------------------------
Title: The NASA-UC Eta-Earth Program. II. A Planet Orbiting HD 156668
with a Minimum Mass of Four Earth Masses
Authors: Howard, Andrew W.; Johnson, John Asher; Marcy, Geoffrey W.;
Fischer, Debra A.; Wright, Jason T.; Henry, Gregory W.; Isaacson,
Howard; Valenti, Jeff A.; Anderson, Jay; Piskunov, Nikolai E.
2011ApJ...726...73H Altcode: 2010arXiv1003.3444H
We report the discovery of HD 156668 b, an extrasolar planet with a
minimum mass of MP sin i = 4.15 M ⊕. This planet
was discovered through Keplerian modeling of precise radial velocities
from Keck-HIRES and is the second super-Earth to emerge from the NASA-UC
Eta-Earth Survey. The best-fit orbit is consistent with circular and
has a period of P = 4.6455 days. The Doppler semi-amplitude of this
planet, K = 1.89 m s-1, is among the lowest ever detected,
on par with the detection of GJ 581 e using HARPS. A longer period
(P ≈ 2.3 years), low-amplitude signal of unknown origin was also
detected in the radial velocities and was filtered out of the data
while fitting the short-period planet. Additional data are required
to determine if the long-period signal is due to a second planet,
stellar activity, or another source. Photometric observations using the
Automated Photometric Telescopes at Fairborn Observatory show that HD
156668 (an old, quiet K3 dwarf) is photometrically constant over the
radial velocity period to 0.1 mmag, supporting the existence of the
planet. No transits were detected down to a photometric limit of ~3
mmag, ruling out transiting planets dominated by extremely bloated
atmospheres, but not precluding a transiting solid/liquid planet
with a modest atmosphere. Based on observations obtained at the
W. M. Keck Observatory, which is operated jointly by the University
of California and the California Institute of Technology. Keck time
has been granted by both NASA and the University of California.

---------------------------------------------------------
Title: The search for magnetic fields in mercury-manganese stars
Authors: Makaganiuk, V.; Kochukhov, O.; Piskunov, N.; Jeffers, S. V.;
Johns-Krull, C. M.; Keller, C. U.; Rodenhuis, M.; Snik, F.; Stempels,
H. C.; Valenti, J. A.
2011A&A...525A..97M Altcode: 2010arXiv1010.3931M
Context. A subclass of the upper main-sequence chemically peculiar
stars, mercury-manganese (HgMn) stars were traditionally considered to
be non-magnetic, showing no evidence of variability in their spectral
line profiles. However, discoveries of chemical inhomogeneities on
their surfaces imply that this assumption should be investigated. In
particular, spectroscopic time-series of AR Aur, α And, and five other
HgMn stars indicate the presence of chemical spots. At the same time,
no signatures of global magnetic fields have been detected. 
Aims: We attempt to understand the physical mechanism that causes the
formation of chemical spots in HgMn stars and gain insight into the
potential magnetic field properties at their surfaces; we performed a
highly sensitive search for magnetic fields for a large set of HgMn
stars. Methods: With the aid of a new polarimeter attached
to the HARPS spectrometer at the ESO 3.6 m-telescope, we obtained
high-quality circular polarization spectra of 41 single and double HgMn
stars. Using a multi-line analysis technique on each star, we co-added
information from hundreds of spectral lines to ensure significantly
greater sensitivity to the presence of magnetic fields, including very
weak fields. Results: For the 47 individual objects studied,
including six components of SB2 systems, we do not detect any magnetic
fields at greater than the 3σ level. The lack of detection in the
circular polarization profiles indicates that if strong fields are
present on these stars, they must have complex surface topologies. For
simple global fields, our detection limits imply upper limits to the
fields present of 2-10 Gauss in the best cases. Conclusions:
We conclude that HgMn stars lack large-scale magnetic fields, which
is typical of spotted magnetic Ap stars, of sufficient strength to
form and sustain the chemical spots observed on HgMn stars. Our study
confirms that in addition to magnetically altered atomic diffusion,
there exists another differentiation mechanism operating in the
atmospheres of late-B main sequence stars that can produce compositional
inhomogeneities on their surfaces. Based on observations collected
at the European Southern Observatory, Chile (ESO programs 083.D-1000,
084.D-0338, 085.D-0296).Figure 5 is only available in electronic form
at <A href="http://www.aanda.org">http://www.aanda.org</A>

---------------------------------------------------------
Title: Magnetic Fields of M-Dwarfs from the Molecular and Atomic
Diagnostics
Authors: Shulyak, D.; Reiners, A.; Wende, S.; Kochukhov, O.; Piskunov,
N.; Seifahrt, A.
2011mast.conf..280S Altcode:
Strong surface magnetic fields are frequently found in the spectra
of M-dwarfs, with the mean intensities on the order of a few thousand
Gauss - three orders of magnitude higher than the mean surface magnetic
field of the Sun. The appearance of such fields in both partially
and fully convective M-dwarfs provides strong constraints on the
theoretical models of stellar magnetism. The accurate estimates of the
magnetic field intensity and geometry in these cool objects, however,
is strongly limited to our ability to simulate the Zeeman effect in
molecular lines. Here we present the first quantitative results of
modelling and analysis of the magnetic fields in selected M-dwarfs
in FeH Wing-Ford F^4Δ-X^4Δ transitions and some strong atomic lines
from polarised radiative transfer.

---------------------------------------------------------
Title: New release of Vienna Atomic Line Database (VALD) and its
integration in Virtual Atomic and Molecular Data Centre (VAMDC)
Authors: Ryabchikova, T. A.; Pakhomov, Yu. V.; Piskunov, N. E.
2011KIzKU.153...61R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Least-squares deconvolution of the stellar intensity and
polarization spectra
Authors: Kochukhov, O.; Makaganiuk, V.; Piskunov, N.
2010A&A...524A...5K Altcode: 2010arXiv1008.5115K
Context. Least-squares deconvolution (LSD) is a powerful method of
extracting high-precision average line profiles from the stellar
intensity and polarization spectra. This technique is widely
used for detection, characterization, and detailed mapping of the
temperature, magnetic, and chemical abundance structures on the
surfaces of stars. Aims: Despite its common usage, the LSD
method is poorly documented and has never been tested with realistic
synthetic spectra. In this study we revisit the key assumptions of
the LSD technique, clarify its numerical implementation, discuss
possible improvements and give recommendations of how to make LSD
results understandable and reproducible. We also address the problem
of interpretation of the moments and shapes of the LSD profiles in
terms of physical parameters. Methods: We have developed an
improved, multiprofile version of LSD (iLSD) and have extended the
deconvolution procedure to linear polarization analysis taking into
account anomalous Zeeman splitting of spectral lines. The iLSD method
is applied to the theoretical Stokes parameter spectra computed
for a wide wavelength interval containing all relevant spectral
lines. We test various methods of interpreting the mean profiles,
investigating how coarse approximations of the multiline technique
translate into errors of the derived parameters. Results: We
find that, generally, the Stokes parameter LSD profiles do not behave
as a real spectral line with respect to the variation of magnetic
field and elemental abundance. This problem is especially prominent
for the Stokes I (intensity) variation with abundance and Stokes Q
(linear polarization) variation with magnetic field. At the same time,
the Stokes V (circular polarization) LSD spectra closely resemble the
profile of a properly chosen synthetic line for the magnetic field
strength up to 1 kG. The longitudinal field estimated from the Stokes
V LSD profile is accurate to within 10% for the field strength below
5 kG and to within a few percent for the fields weaker than 1 kG. Our
iLSD technique offers clear advantages over the standard LSD method
in the individual analysis of different chemical elements. 
Conclusions: We conclude that the usual method of interpreting the
LSD profiles by assuming that they are equivalent to a real spectral
line gives satisfactory results only in a limited parameter range and
thus should be applied with caution. A more trustworthy approach is
to abandon the single-line approximation of the average profiles and
apply LSD consistently to observations and synthetic spectra.

---------------------------------------------------------
Title: VizieR Online Data Catalog: Observations of II Peg (Lindborg+,
2011)
Authors: Lindborg, M.; Korpi, M. J.; Hackman, T.; Tuominen, I.; Ilyin,
I.; Piskunov, N.
2010yCat..35260044L Altcode: 2010yCat..35269044L
The observations were collected with the SOFIN spectrograph at the
Nordic Optical Telescope. The temperature maps were calculated using
a Doppler imaging code based on Tikhonov regularization. (1
data file).

---------------------------------------------------------
Title: Modelling the molecular Zeeman-effect in M-dwarfs: methods
and first results
Authors: Shulyak, D.; Reiners, A.; Wende, S.; Kochukhov, O.; Piskunov,
N.; Seifahrt, A.
2010A&A...523A..37S Altcode: 2010arXiv1008.2512S
 Aims: We present first quantitative results of the surface
magnetic field measurements in selected M-dwarfs based on detailed
spectra synthesis conducted simultaneously in atomic and molecular
lines of the FeH Wing-Ford F4 Δ - X4 Δ
transitions. Methods: A modified version of the Molecular Zeeman
Library (MZL) was used to compute Landé g-factors for FeH lines in
different Hund's cases. Magnetic spectra synthesis was performed with
the Synmast code. Results: We show that the implementation
of different Hund's case for FeH states depending on their quantum
numbers allows us to achieve a good fit to the majority of lines in
a sunspot spectrum in an automatic regime. Strong magnetic fields are
confirmed via the modelling of atomic and FeH lines for three M-dwarfs
YZ CMi, EV Lac, and AD Leo, but their mean intensities are found
to be systematically lower than previously reported. A much weaker
field (1.7-2 kG against 2.7 kG) is required to fit FeH lines in the
spectra of GJ 1224. Conclusions: Our method allows us to measure
average magnetic fields in very low-mass stars from polarized radiative
transfer. The obtained results indicate that the fields reported in
earlier works were probably overestimated by about 15-30%. Higher
quality observations are needed for more definite results.

---------------------------------------------------------
Title: The California Planet Survey. I. Four New Giant Exoplanets
Authors: Howard, Andrew W.; Johnson, John Asher; Marcy, Geoffrey W.;
Fischer, Debra A.; Wright, Jason T.; Bernat, David; Henry, Gregory W.;
Peek, Kathryn M. G.; Isaacson, Howard; Apps, Kevin; Endl, Michael;
Cochran, William D.; Valenti, Jeff A.; Anderson, Jay; Piskunov,
Nikolai E.
2010ApJ...721.1467H Altcode: 2010arXiv1003.3488H
We present precise Doppler measurements of four stars obtained during
the past decade at Keck Observatory by the California Planet Survey
(CPS). These stars, namely, HD 34445, HD 126614, HD 13931, and Gl
179, all show evidence for a single planet in Keplerian motion. We
also present Doppler measurements from the Hobby-Eberly Telescope
(HET) for two of the stars, HD 34445 and Gl 179, that confirm the
Keck detections and significantly refine the orbital parameters. These
planets add to the statistical properties of giant planets orbiting near
or beyond the ice line, and merit follow-up by astrometry, imaging, and
space-borne spectroscopy. Their orbital parameters span wide ranges
of planetary minimum mass (M sin i = 0.38-1.9 M Jup),
orbital period (P = 2.87-11.5 yr), semimajor axis (a = 2.1-5.2 AU),
and eccentricity (e = 0.02-0.41). HD 34445 b (P = 2.87 yr, M sin i =
0.79 M Jup, e = 0.27) is a massive planet orbiting an old,
G-type star. We announce a planet, HD 126614 Ab, and an M dwarf, HD
126614 B, orbiting the metal-rich star HD 126614 (which we now refer to
as HD 126614 A). The planet, HD 126614 Ab, has minimum mass M sin i =
0.38 M Jup and orbits the stellar primary with period P =
3.41 yr and orbital separation a = 2.3 AU. The faint M dwarf companion,
HD 126614 B, is separated from the stellar primary by 489 mas (33 AU)
and was discovered with direct observations using adaptive optics and
the PHARO camera at Palomar Observatory. The stellar primary in this
new system, HD 126614 A, has the highest measured metallicity ([Fe/H] =
+0.56) of any known planet-bearing star. HD 13931 b (P = 11.5 yr, M sin
i = 1.88 M Jup, e = 0.02) is a Jupiter analog orbiting a near
solar twin. Gl 179 b (P = 6.3 yr, M sin i = 0.82 M Jup, e =
0.21) is a massive planet orbiting a faint M dwarf. The high metallicity
of Gl 179 is consistent with the planet-metallicity correlation among
M dwarfs, as documented recently by Johnson &amp; Apps. Based on
observations obtained at the W. M. Keck Observatory, which is operated
jointly by the University of California and the California Institute of
Technology. Keck time has been granted by both NASA and the University
of California. Two of the planets announced here are also based on
observations obtained with the Hobby-Eberly Telescope, which is a
joint project of the University of Texas at Austin, the Pennsylvania
State University, Stanford University, Ludwig-Maximilians-Universität
München, and Georg-August-Universität Göttingen.

---------------------------------------------------------
Title: VAMDC: The Virtual Atomic and Molecular Data Centre: a Service
Orientated Data Infrastructure for e- Research
Authors: Mason, N. J.; Dubernet, M. L.; Benson, K. M.; Bureau, J.;
Heiter, U.; Kupka, F.; Le Sidaner, P.; Piskunov, N.; Rixon, G. T.;
Schlemmer, S.; Shih, A.; Tennyson, J.; Walton, N.; Witherick, D. W.
2010epsc.conf..861M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Stability of spectroscopic data reduction
Authors: Piskunov, Nikolai
2010aepr.confE..42P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: SIMPLE: a high-resolution near-infrared spectrometer for
the E-ELT
Authors: Origlia, Livia; Oliva, Ernesto; Maiolino, Roberto; Gustafsson,
Bengt; Piskunov, Nikolai; Kochucov, Oleg; Vanzi, Leonardo; Minniti,
Dante; Zoccali, Manuela; Hatzes, Artie; Guenther, Eike
2010SPIE.7735E..2BO Altcode: 2010SPIE.7735E..78O
SIMPLE is an optimized near IR echelle spectrograph for the E-ELT
assisted by adaptive optics. It delivers a complete 0.84-2.5μm spectrum
in one exposure with resolution up to R=130,000, nearly diffraction
limited pixel scale and limiting magnitudes down to JHK~20. Its most
prominent science cases include the study of the intergalactic medium
in the early Universe (z&gt;6) and of the atmospheres of exo-planet
transiting nearby low mass stars.

---------------------------------------------------------
Title: Doppler images of the RS CVn binary II Pegasi during the
years 1994-2002
Authors: Lindborg; M.; Korpi; J., M.; Hackman; T.; Tuominen; I.;
Ilyin; I.; Piskunov; N
2010arXiv1006.3060L Altcode:
We publish 16 Doppler imaging temperature maps for the years 1994-2002
of the active RS CVn star II Peg. The six maps from 1999-2002 are
based on previously unpublished observations. Through Doppler imaging
we want to study the spot evolution of the star and in particular
compare this with previous results showing a cyclic spot behaviour and
persistent active longitudes. The observations were collected with the
SOFIN spectrograph at the Nordic Optical Telescope. The temperature
maps were calculated using a Doppler imaging code based on Tikhonov
regularization. During 1994-2001, our results show a consistent trend
in the derived longitudes of the principal and secondary temperature
minima over time such that the magnetic structure appears to rotate
somewhat more rapidly than the orbital period of this close binary. A
sudden phase jump of the active region occured between the observing
seasons of 2001 and 2002. No clear trend over time is detected in the
derived latitudes of the spots, indicating that the systematic motion
could be related to the drift of the spot generating mechanism rather
than to differential rotation. The derived temperature maps are quite
similar to the ones obtained earlier with a different methods, the main
differences occurring in the spot latitudes and relative strength of
the spot structures. We observe both longitude and latitude shifts in
the spot activity of II Peg. However, our results are not consistent
with the periodic behaviour presented in previous studies.

---------------------------------------------------------
Title: Commission 29: Stellar Spectra
Authors: Piskunov, Nikolai; Cunha, Katia; Parthasarathy, Mudumba;
Aoki, Wako; Asplund, Martin; Bohlender, David; Carpenter, Kenneth;
Melendez, Jorge; Parthasarathy, Mudumba; Rossi, Silvia; Smith, Verne;
Soderblom, David; Wahlgren, Glenn
2010IAUTB..27..193P Altcode:
The business meeting was attended by 23 members of the Commission. The
meeting started at 16:00 a short report of the activities during the
triennium 2006-2009. The focus of the activities was the sharing
of expertise between spectroscopic techniques in various areas of
astronomical research. In particular, the progress in instrumentation,
detectors, data reduction, data analysis and archiving. The second
activity was the analysis of to IAU meeting proposals followed by
recommendations for improvements and eventually support. The sponsored
symposia included Sponsoring symposia The Ages of Stars and The Disk
Galaxy Evolution in the Cosmological Context. The Commission was also
disseminating information about the Commission activities and relevant
meetings to the Commission members. In this respect the Commission
web page is playing a crucial role.

---------------------------------------------------------
Title: INTER-DIVISION IV-V WORKING GROUP on Ap and Related Stars
Authors: Cunha, Margarida S.; Weiss, Werner; Dworetsky, Mike;
Kochukhov, Oleg; Kupka, Friedrich; Leblanc, Francis; Monier, Richard;
Paunzen, Ernst; Piskunov, Nikolai; Shibahashi, Hiromoto; Smalley,
Barry; Ziznovsky, Jozef
2010IAUTB..27..205C Altcode:
The business meeting started at 11h00, in the presence of 18 members,
with a brief summary of the activities and achievements of the Working
group during the triennium 2006-2009.

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Title: Surface temperature maps for II Peg during 1999-2002
Authors: Lindborg, M.; Korpi, M. J.; Tuominen, I.; Hackman, T.; Ilyin,
I.; Piskunov, N.
2010IAUS..264..213L Altcode: 2009arXiv0911.0198L
The active RS CVn star II Peg has been spectroscopically monitored for
almost 18 years with the SOFIN spectrograph at NOT, La Palma, Spain. In
this paper we present five new surface temperature maps of the object
for the years 1999 (two maps), 2001 (one map) and 2002 (two maps).

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Title: Surface structure of the CoRoT CP2 target star HD 50773
Authors: Lüftinger, T.; Fröhlich, H. -E.; Weiss, W. W.; Petit, P.;
Aurière, M.; Nesvacil, N.; Gruberbauer, M.; Shulyak, D.; Alecian,
E.; Baglin, A.; Baudin, F.; Catala, C.; Donati, J. -F.; Kochukhov,
O.; Michel, E.; Piskunov, N.; Roudier, T.; Samadi, R.
2010A&A...509A..43L Altcode: 2009arXiv0911.3791L
 Aims: We compare surface maps of the chemically peculiar
star HD 50773 produced with a Bayesian technique and based on
high quality CoRoT photometry with those derived from rotation
phase resolved spectropolarimetry. The goal is to investigate the
correlation of surface brightness with surface chemical abundance
distribution and the stellar magnetic surface field. Methods:
The rotational period of the star was determined from a nearly 60
days long continuous light curve obtained during the initial run of
CoRoT. Using a Bayesian approach to star-spot modelling, which in this
work is applied for the first time for the photometric mapping of a CP
star, we derived longitudes, latitudes and radii of four different spot
areas. Additional parameters like stellar inclination and the spot's
intensities were also determined. The CoRoT observations triggered an
extensive ground-based spectroscopic and spectropolarimetric observing
campaign and enabled us to obtain 19 different high resolution spectra
in Stokes parameters I and V with NARVAL, ESPaDOnS, and SemelPol
spectropolarimeters. Doppler and Magnetic Doppler imaging techniques
allowed us to derive the magnetic field geometry of the star and the
surface abundance distributions of Mg, Si, Ca, Ti, Cr, Fe, Ni, Y, and
Cu. Results: We find a dominant dipolar structure of the surface
magnetic field. The CoRoT light curve variations and abundances of
most elements mapped are correlated with the aforementioned geometry:
Cr, Fe, and Si are enhanced around the magnetic poles and coincide
with the bright regions on the surface of HD 50773 as predicted by our
light curve synthesis and confirmed by photometric imaging. The
CoRoT space mission was developed and is operated by the French space
agency CNES, with participation of ESA's RSSD and Science Pograms,
Austria, Belgium, Brazil, Germany, and Spain.

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Title: Time-resolved photometric and spectroscopic analysis of the
luminous Ap star HD103498
Authors: Joshi, S.; Ryabchikova, T.; Kochukhov, O.; Sachkov, M.;
Tiwari, S. K.; Chakradhari, N. K.; Piskunov, N.
2010MNRAS.401.1299J Altcode: 2009MNRAS.tmp.1638J; 2009arXiv0909.3906J
We present the results of the photometric and spectroscopic monitoring
of the luminous Ap star HD103498. The time-series photometric
observations were carried out on 17 nights using a three-channel fast
photometer attached to the 1.04-m optical telescope at the Aryabhatta
Research Institute of Observational Sciences (ARIES), Nainital. The
photometric data from five nights in 2007 show a clear signature of
15-min periodicity. However, the follow-up observations during 2007-2009
did not reproduce any such periodicity. To confirm the photometric
light variations, time-series spectroscopic observations were carried
out with the 2.56-m Nordic Optical Telescope (NOT) at La Palma on 2009
February 2. No radial velocity variations were present in this data
set, which is in full agreement with the photometric observations
taken around the same date. Model atmosphere and abundance analysis
of HD103498 show that the star is evolved from the main sequence and
its atmospheric abundances are similar to those of two other evolved
Ap stars, HD133792 and HD204411: large overabundances of Si, Cr and Fe
and moderate overabundances of the rare-earth elements. These chemical
properties and a higher effective temperature distinguish HD103498
from any known roAp star.

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Title: The Eta-Earth Survey for Low-Mass Exoplanets
Authors: Howard, Andrew; Marcy, G.; Fischer, D.; Johnson, J.; Wright,
J.; Valenti, J.; Anderson, J.; Piskunov, N.; Isaacson, H.; Brewer,
J.; Clubb, K.; Lin, D.; Ida, S.
2010AAS...21534806H Altcode: 2010BAAS...42..530H
The NASA-UC Eta-Earth Survey by the California Planet Search (CPS)
group is a systematic search for low-mass planets ( 3-30 Earth
masses) orbiting the nearest 230 GKM stars suitable for high-precision
Doppler observations at Keck Observatory. These 1 m/s measurements of
a well-defined sample of nearby stars will provide one of the first
estimates of the fraction of stars with Earth-like planets. The talk
will describe recently announced super-Earths and Neptune-mass planets
from the Eta-Earth Survey, including the 9 Earth mass planet HD 7924b
and others. These low-mass planets are extraordinarily valuable in
their own right, as targets for transit and other follow-up studies,
and as windows into the mechanisms of planet formation. Low mass
planets show several emerging trends in their orbital parameters and
in the characteristics of their host stars. For example, super-Earth
and Neptune-mass planets preferentially orbit stars with lower mass
(Mstar &lt; 0.8 solar masses), in contrast to the trend
seen in higher mass planets. The survey observations are nearly
complete, allowing us to place initial constraints on the population
of super-Earth and Neptune-mass planets, and, using planet-formation
theory, to extrapolate to the fraction of Earth-mass planets and 1
year orbits.

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Title: Magnetic Doppler imaging of the roAp star HD 24712
Authors: Lüftinger, T.; Kochukhov, O.; Ryabchikova, T.; Piskunov,
N.; Weiss, W. W.; Ilyin, I.
2010A&A...509A..71L Altcode: 2009arXiv0910.5556L
 Aims: We present the first magnetic Doppler images of a rapidly
oscillating Ap (roAp) star. Methods: We deduce information about
magnetic field geometry and abundance distributions of a number of
chemical elements on the surface of the hitherto best studied roAp star,
HD 24712, using the magnetic Doppler imaging (MDI) code, invers10,
which allows us to reconstruct simultaneously and consistently the
magnetic field geometry and elemental abundance distributions on
a stellar surface. For this purpose we analyse time series spectra
obtained in Stokes I and V parameters with the SOFIN polarimeter at the
Nordic Optical Telescope and recover surface abundance structures of
sixteen different chemical elements, respectively ions, including Mg,
Ca, Sc, Ti, Cr, Fe, Co, Ni, Y, La, Ce, Pr, Nd, Gd, Tb, and Dy. For
the rare earth elements (REE) Pr and Nd separate maps were obtained
using lines of the first and the second ionization stage. 
Results: We find and confirm a clear dipolar structure of the surface
magnetic field and an unexpected correlation of elemental abundance
with respect to this field: one group of elements accumulates solely
where the positive magnetic pole is visible, whereas the other group
avoids this region and is enhanced where the magnetic equatorial
region dominates the visible stellar surface. We also observe relative
shifts of abundance enhancement- or depletion regions between the
various elements exhibiting otherwise similar behaviour. Based
on observations made with the Nordic Optical Telescope, operated on
the island of La Palma jointly by Denmark, Finland, Iceland, Norway,
and Sweden, in the Spanish Observatorio del Roque de los Muchachos of
the Instituto de Astrofisica de Canarias.

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Title: Detection of dusty plasma near the E-ring of Saturn
Authors: Wahlund, J. -E.; André, M.; Eriksson, A. I. E.; Lundberg,
M.; Morooka, M. W.; Shafiq, M.; Averkamp, T. F.; Gurnett, D. A.;
Hospodarsky, G. B.; Kurth, W. S.; Jacobsen, K. S.; Pedersen, A.;
Farrell, W.; Ratynskaia, S.; Piskunov, N.
2009P&SS...57.1795W Altcode:
We present several independent in-situ measurements, which provide
evidence that charged dust in the E-ring interacts collectively with
the dense surrounding plasma disk of Saturn, i.e., form a system of
dust-plasma interaction. The results are based on data sampled by the
Radio and Plasma Wave Science (RPWS) investigation onboard Cassini,
which allows for interferometry of plasma density inhomogeneities
(δ n/ n) with two antenna elements and a Langmuir probe sensor. The
interferometer experiment detects two ion populations; one co-rotating
with the planetary magnetic field and another moving with near Keplerian
speed around Saturn. The full range of RPWS measurements indicates that
the Keplerian population consists of colder ions ( Ti&lt;few
eV), which would interact with the electrical potential cavities
associated with the few volts negatively charged E-ring water-rich
dust grains. The presence of the charged dust inhibits E× B pick-up
of freshly ionized particles by the rotating magnetic field of Saturn,
since the local potential gradients near the dust grains are stronger
than the large-scale co-rotation electric field. Even so, most ions
are eventually energised to energies above the dust potentials of a
few volts and become part of a hotter co-rotating ion population. The
observed results have direct relevance to the interactions occurring in
planet forming accretion disks around young stars, since the physical
environment is similar.

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Title: Magnetic Doppler Imaging of Active Stars
Authors: Kochukhov, O.; Piskunov, N.
2009ASPC..405..539K Altcode:
We present a new implementation of the magnetic Doppler imaging
technique, which aims at self-consistent temperature and magnetic
mapping of the surface structures in cool active stars. Our magnetic
imaging procedure is unique in its capability to model individual
spectral features in all four Stokes parameters. We discuss performance
and intrinsic limitations of the new magnetic Doppler imaging
method. A special emphasis is given to the simultaneous modeling of
the magnetically sensitive lines in the optical and infrared regions
and to combining information from both atomic and molecular spectral
features. These two techniques may, for the first time, give us a tool
to study magnetic fields in the starspot interiors.

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Title: The NASA-UC Eta-Earth Program. I. A Super-Earth Orbiting
HD 7924
Authors: Howard, Andrew W.; Johnson, John Asher; Marcy, Geoffrey W.;
Fischer, Debra A.; Wright, Jason T.; Henry, Gregory W.; Giguere,
Matthew J.; Isaacson, Howard; Valenti, Jeff A.; Anderson, Jay;
Piskunov, Nikolai E.
2009ApJ...696...75H Altcode: 2009arXiv0901.4394H
We report the discovery of the first low-mass planet to emerge from
the NASA-UC Eta-Earth Program, a super-Earth orbiting the K0 dwarf HD
7924. Keplerian modeling of precise Doppler radial velocities reveals
a planet with minimum mass MP sin i = 9.26 M ⊕
in a P = 5.398 d orbit. Based on Keck-HIRES measurements from 2001 to
2008, the planet is robustly detected with an estimated false alarm
probability of less than 0.001. Photometric observations using the
Automated Photometric Telescopes at Fairborn Observatory show that HD
7924 is photometrically constant over the radial velocity period to 0.19
mmag, supporting the existence of the planetary companion. No transits
were detected down to a photometric limit of ~0.5 mmag, eliminating
transiting planets with a variety of compositions. HD 7924b is one
of only eight planets detected by the radial velocity technique with
MP sin i &lt; 10 M ⊕ and as such is a member
of an emerging family of low-mass planets that together constrain
theories of planet formation. Based on observations obtained at
the W. M. Keck Observatory, which is operated jointly by the University
of California and the California Institute of Technology. Keck time
has been granted by both NASA and the University of California.

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Title: Cartography of the magnetic fields and chemical spots of
Ap stars
Authors: Silvester, James; Kochukhov, O.; Wade, G. A.; Piskunov, N.;
Landstreet, J. D.; Bagnulo, S.
2009IAUS..259..403S Altcode:
We will introduce a project using Magnetic Doppler Imaging (MDI) to
create assumption-free vector magnetic field maps and chemical surface
structure maps of chemically peculiar A and B type (or Ap) stars. We
are exploiting the latest generation of spectropolarimeters (NARVAL at
the Pic du Midi observatory, and ESPaDOnS at the Canada-France-Hawaii
telescope), to obtain high-resolution time series of Stokes IQUV spectra
of a selection of Ap stars. The spectra have superior signal-to-noise
ratio, resolution and wavelength coverage to those used previously. This
combined with the ground-breaking inversion techniques introduced
by Kochukhov et al. (2002) results in maps which represent the
state-of-the-art in the field of stellar cartography. These maps will
allow us to better understand the links between the magnetic field and
the physical processes leading to the formation of chemical structures
in the photosphere and allow us to address questions surrounding the
detailed magnetic field geometry of Ap stars.

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Title: Planet formation bursts at the borders of the dead zone in
2D numerical simulations of circumstellar disks
Authors: Lyra, W.; Johansen, A.; Zsom, A.; Klahr, H.; Piskunov, N.
2009A&A...497..869L Altcode: 2009arXiv0901.1638L
Context: As accretion in protoplanetary disks is enabled by
turbulent viscosity, the border between active and inactive (dead)
zones constitutes a location where there is an abrupt change in
the accretion flow. The gas accumulation that ensues triggers the
Rossby wave instability, which in turn saturates into anticyclonic
vortices. It has been suggested that the trapping of solids within them
leads to a burst of planet formation on very short timescales. Aims: We study in the formation and evolution of the vortices
in greater detail, focusing on the implications for the dynamics
of embedded solid particles and planet formation. Methods:
We performed two-dimensional global simulations of the dynamics of
gas and solids in a non-magnetized thin protoplanetary disk with the
Pencil code. We used multiple particle species of radius 1, 10, 30,
and 100 cm. We computed the particles' gravitational interaction by a
particle-mesh method, translating the particles' number density into
surface density and computing the corresponding self-gravitational
potential via fast Fourier transforms. The dead zone is modeled as a
region of low viscosity. Adiabatic and locally isothermal equations of
state are used. Results: The Rossby wave instability is triggered
under a variety of conditions, thus making vortex formation a robust
process. Inside the vortices, fast accumulation of solids occurs and
the particles collapse into objects of planetary mass on timescales
as short as five orbits. Because the drag force is size-dependent,
aerodynamical sorting ensues within the vortical motion, and the first
bound structures formed are composed primarily of similarly-sized
particles. In addition to erosion due to ram pressure, we identify
gas tides from the massive vortices as a disrupting agent of formed
protoplanetary embryos. We find evidence that the backreaction of the
drag force from the particles onto the gas modifies the evolution of
the Rossby wave instability, with vortices being launched only at later
times if this term is excluded from the momentum equation. Even though
the gas is not initially gravitationally unstable, the vortices can
grow to Q ≈ 1 in locally isothermal runs, which halts the inverse
cascade of energy towards smaller wavenumbers. As a result, vortices
in models without self-gravity tend to rapidly merge towards a m =
2 or m =1 mode, while models with self-gravity retain dominant higher
order modes (m = 4 or m = 3) for longer times. Non-selfgravitating
disks thus show fewer and stronger vortices. We also estimate the
collisional velocity history of the particles that compose the most
massive embryo by the end of the simulation, finding that the vast
majority of them never experienced a collision with another particle
at speeds faster than 1 m s-1. This result lends further
support to previous studies showing that vortices provide a favorable
environment for planet formation.

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Title: Magnetic Doppler imaging of II Peg
Authors: Kochukhov, Oleg; Piskunov, N.; Ilyin, I.; Tuominen, I.
2009IAUS..259..439K Altcode:
Rotational modulation of the intensity and polarization spectra of
magnetic stars offers a unique possibility to reconstruct the structure
of surface magnetic fields and to investigate their relation to cool
starspots. We have developed a new magnetic Doppler imaging code which
aims at self-consistent temperature and magnetic mapping of cool
active stars. Here we present magnetic Doppler imaging analysis of
high-resolution circular polarization observations of the active star
II Peg. We demonstrate that a self-consistent approach to magnetic
inversion unveils stronger magnetic fields than found previously
through disjoint analyses of polarization and intensity observations
of active stars.

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Title: Magnetic Doppler Imaging of Active Stars
Authors: Kochukhov, O.; Piskunov, N.; Ilyin, I.; Tuominen, I.
2009AIPC.1094..720K Altcode: 2007arXiv0712.2745K; 2009csss...15..720K
We present a new magnetic Doppler imaging code which aims at
self-consistent temperature and magnetic mapping of cool active
stars. Our magnetic imaging procedure is unique in its capability
to interpret rotational modulation of individual spectral features
in all four Stokes parameters. We discuss performance and intrinsic
limitations of our magnetic Doppler imaging method and present results
of the simultaneous reconstruction of temperature spots and magnetic
field on active star II Peg.

---------------------------------------------------------
Title: Magnetic fields in M dwarf stars from high-resolution infrared
spectra
Authors: Kochukhov, O.; Heiter, U.; Piskunov, N.; Ryde, N.; Gustafsson,
B.; Bagnulo, S.; Plez, B.
2009AIPC.1094..124K Altcode: 2009csss...15..124K
Magnetic fields play a central role in the atmospheric properties
and variability of active M dwarfs. Information on the strength and
structure of magnetic fields in these objects is vital for understanding
dynamo mechanisms and magnetically-driven activity of low-mass stars,
and for constraining theories of star formation and evolution. We have
initiated the first systematic high-resolution survey of magnetically
sensitive infrared spectral lines in M dwarf stars using the CRIRES
instrument at the ESO VLT. We have completed observations for a sample
of 35 active and inactive M dwarfs. Here we report first results of our
project, demonstrating a clear detection of magnetic splitting of lines
in the spectra of several M dwarfs. We assess diagnostic potential of
different Zeeman-sensitive lines in the observed spectral region and
apply spectrum synthesis modelling to infer magnetic field properties
of selected M dwarfs.

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Title: Transiting Planets in the Galactic Bulge from SWEEPS Survey
and Implications
Authors: Sahu, Kailash C.; Casertano, Stefano; Valenti, Jeff; Bond,
Howard E.; Brown, Thomas M.; Smith, T. Ed; Clarkson, Will; Minniti,
Dante; Zoccali, Manuela; Livio, Mario; Renzini, Alvio; Rich, R. M.;
Panagia, Nino; Lubow, Stephen; Brown, Timothy; Piskunov, Nikolai
2009IAUS..253...45S Altcode:
The SWEEPS (Sagittarius Window Eclipsing Extrasolar Planet Search)
program was aimed at detecting planets around stars in the Galactic
bulge, not only to determine their physical properties, but also
to determine whether the properties of planets found in the solar
neighborhood, such as their frequency and the metallicity dependence,
also hold for the planets in the Galactic bulge. We used the Hubble
Space Telescope to monitor 180,000 F, G, K, and M dwarfs in the
Galactic bulge continuously for 7 days in order to look for transiting
planets. We discovered 16 candidate transiting extrasolar planets
with periods of 0.6 to 4.2 days, including a possible new class of
ultra-short period planets (USPPs) with P &lt; 1 day. The facts that
(i) the coverage in the monitoring program is continuous, (ii) most
of the stars are at a known distance (in the Galctic bulge), (iii)
monitoring was carried out in 2 passbands, and (iv) the images have
high spatial resolution, were crucial in minimizing and estimating the
false positive rates. We estimate that at least 45% of the candidates
are genuine planets. Radial velocity observations of the two brightest
host stars further support the planetary nature of the transiting
companions. These results suggest that the planet frequency in the
Galactic bulge is similar to that in the solar neighborhood. They
also suggest that higher metallicity favors planet formation even
in the Galactic bulge. The USPPs occur only around low-mass stars
which may suggest that close-in planets around higher-mass stars are
irradiately evaporated, or that planets are able to migrate to and
survive in close-in orbits only around such old and low-mass stars.

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Title: Standing on the shoulders of giants. Trojan Earths and vortex
trapping in low mass self-gravitating protoplanetary disks of gas
and solids
Authors: Lyra, W.; Johansen, A.; Klahr, H.; Piskunov, N.
2009A&A...493.1125L Altcode: 2008arXiv0810.3192L
Context: Centimeter and meter-sized solid particles in protoplanetary
disks are trapped within long-lived, high-pressure regions, creating
opportunities for collapse into planetesimals and planetary embryos. Aims: We aim to study the effect of the high-pressure regions
generated in the gaseous disks by a giant planet perturber. These
regions consist of gas retained in tadpole orbits around the stable
Lagrangian points as a gap is carved, and the Rossby vortices launched
at the edges of the gap. Methods: We performed global simulations
of the dynamics of gas and solids in a low mass non-magnetized
self-gravitating thin protoplanetary disk. We employed the Pencil
code to solve the Eulerian hydro equations, tracing the solids with
a large number of Lagrangian particles, usually 100 000. To compute
the gravitational potential of the swarm of solids, we solved the
Poisson equation using particle-mesh methods with multiple fast Fourier
transforms. Results: Huge particle concentrations are seen in
the Lagrangian points of the giant planet, as well as in the vortices
they induce at the edges of the carved gaps. For 1 cm to 10 cm radii,
gravitational collapse occurs in the Lagrangian points in less than 200
orbits. For 5 cm particles, a 2M⊕ planet is formed. For 10
cm, the final maximum collapsed mass is around 3M⊕. The
collapse of the 1 cm particles is indirect, following the timescale
of gas depletion from the tadpole orbits. Vortices are excited at the
edges of the gap, primarily trapping particles of 30 cm radii. The
rocky planet that is formed is as massive as 17M⊕,
constituting a Super-Earth. Collapse does not occur for 40 cm
onwards. By using multiple particle species, we find that gas drag
modifies the streamlines in the tadpole region around the classical
L4 and L5 points. As a result, particles of different radii have
their stable points shifted to different locations. Collapse therefore
takes longer and produces planets of lower mass. Three super-Earths are
formed in the vortices, the most massive having 4.5M⊕. Conclusions: A Jupiter-mass planet can induce the formation of other
planetary embryos at the outer edge of its gas gap. Trojan Earth-mass
planets are readily formed; although not existing in the solar system,
might be common in the exoplanetary zoo.

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Title: Commission 29: Stellar Spectra
Authors: Parthasarathy, Mudumba; Piskunov, Nikolai E.; Sneden,
Christopher; Carpenter, Kenneth G.; Castelli, Fiorella; Cunha, Katia;
Eenens, Phillippe R. J.; Hubeny, Ivan; Rossi, Silvia; Takada-Hidai,
Masahide; Wahlgren, Glenn M.; Weiss, Werner W.
2009IAUTA..27..209P Altcode:
The members of IAU Commission 29 Stellar Spectra are actively
engaged in the quantitative analysis of spectra of various types
of stars. With large and medium size telescopes equipped with high
resolution spectrographs LTE and Non-LTE analysis of spectra of all
types stars are being carried out. Spectra of stars in our Galaxy,
in globular and open clusters, stars in LMC and SMC and in nearby
galaxies are being studied. Accurate chemical composition analysis
of various types of stars has been carried out during the past three
years. Now the analysis of stellar spectra covers the wavelength range
from X-ray region to IR and sub-millimeter range. Recently stellar
spectra are being analysed using time-dependent, 3D, hydrodynamical
model atmospheres to derive accurate stellar abundances.

---------------------------------------------------------
Title: Inter-Division IV-V / Working Group Ap and Related Stars
Authors: Cunha, Margarida S.; Weiss, Werner W.; Dworetsky, Michael M.;
Kochukhov, Oleg; Kupka, Friedrich; Leblanc, Francis; Monier, Richard;
Paunzen, Ernst; Piskunov, Nikolai E.; Shibahashi, Hiromoto; Smalley,
Barry; Ziznovsky, Jozef
2009IAUTA..27..245C Altcode:
The diversity of physical phenomena embraced by the study of Chemically
Peculiar (CP) stars results in an associated research community
with interests that are equally diverse. This fact became once more
evident during the CP#Ap Workshop that took place in Vienna (Austria)
in September 2007, and which gathered over 80 members of this research
community. Besides the excellent scientific outcome of the meeting,
during the workshop the community had the opportunity to discuss its
organization and plans for the future. Following on those plans,
the Working Group has submitted a proposal for a Joint Discussion
during the IAU XXVII General Assembly, in Rio de Janeiro, which has
meanwhile been accepted. Moreover, through an ApN newsletter forum,
the Working Group has compiled requests from the community concerning
atomic and related data. These requests have been put together and
will be shared with Commission 14.

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Title: Embryos grown in the dead zone. Assembling the first
protoplanetary cores in low mass self-gravitating circumstellar
disks of gas and solids
Authors: Lyra, W.; Johansen, A.; Klahr, H.; Piskunov, N.
2008A&A...491L..41L Altcode: 2008arXiv0807.2622L
Context: In the borders of the dead zones of protoplanetary disks, the
inflow of gas produces a local density maximum that triggers the Rossby
wave instability. The vortices that form are efficient in trapping
solids. Aims: We aim to assess the possibility of gravitational
collapse of the solids within the Rossby vortices. Methods:
We perform global simulations of the dynamics of gas and solids in a
low mass non-magnetized self-gravitating thin protoplanetary disk with
the Pencil Code. We use multiple particle species of radius 1, 10, 30,
and 100 cm. The dead zone is modelled as a region of low viscosity. Results: The Rossby vortices excited in the edges of the dead zone
are efficient particle traps. Within 5 orbits after their appearance,
the solids achieve critical density and undergo gravitational collapse
into Mars sized objects. The velocity dispersions are of the order of
10 m s-1 for newly formed embryos, later lowering to less
than 1 m s-1 by drag force cooling. After 200 orbits, over
300 gravitationally bound embryos were formed, 20 of them being more
massive than Mars. Their mass spectrum follows a power law of index
-2.3 ± 0.2. Appendices A-C are only available in electronic form
at http://www.aanda.org

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Title: Doppler imaging
Authors: Piskunov, N.
2008PhST..133a4017P Altcode:
In this paper, I present a short review of the history and modern
status of Doppler imaging techniques, highlighting their dependence
on the knowledge of the fundamental stellar parameters, the quality
of stellar atmospheric models and the accuracy of spectral synthesis.

---------------------------------------------------------
Title: Vald
Authors: Obbrugger, M.; Heiter, U.; Kupka, F.; Lüftinger, T.;
Nesvacil, N.; Piskunov, N.; Ryabchikova, T. A.; Stempels, H. C.;
Stütz, Ch.; Weiss, W. W.
2008asvo.proc..215O Altcode:
VALD is a collection of atomic transition parameters and supporting
extraction software. VALD services are available via Email (VALD-EMS)
and the Web interface. Different kinds of requests are useful for
several needs like abundance analysis, radial velocity measurements,
or line identification. Since 1994, the early days of VALD, the database
has been constantly improved and the release of VALD-3 - incorporating,
e.g., molecular data and new line lists - is in preparation. With
meanwhile more than 5 000 000 requests VALD developed to a much
appreciated tool.

---------------------------------------------------------
Title: VALD — an atomic and molecular database for astrophysics
Authors: Heiter, U.; Barklem, P.; Fossati, L.; Kildiyarova, R.;
Kochukhov, O.; Kupka, F.; Obbrugger, M.; Piskunov, N.; Plez, B.;
Ryabchikova, T.; Stempels, H. C.; Stütz, Ch; Weiss, W. W.
2008JPhCS.130a2011H Altcode:
The VALD database of atomic and molecular data aims to ensure a robust
and consistent analysis of astrophysical spectra. We offer a convenient
e-mail and web-based user interface to a vast collection of spectral
line parameters for all chemical elements and in the future also for
molecules. An international team is working on the following tasks:
collecting line parameters from relevant theoretical and experimental
publications, computing line parameters, evaluating the data quality by
comparison of similar data from different sources and by comparison
with astrophysical observations, and incorporating the data into
VALD. A unique feature of VALD is its capability to provide the most
comprehensive spectral line lists for specific astrophysical plasma
conditions defined by the user.

---------------------------------------------------------
Title: A comparative analysis of the laboratory and theoretical
transition probabilities of the Fe-peak elements for a new release
of VALD
Authors: Ryabchikova, T.; Kildiyarova, R.; Piskunov, N.; Heiter, U.;
Fossati, L.; Weiss, W. W.
2008JPhCS.130a2017R Altcode:
We carried out a comparative analysis of the recent atomic data for
iron-peak elements, mainly Ti, Cr and Fe, for a new release of the
Vienna Atomic Line Database (VALD3). New data were compared with
those available in VALD2 and were checked using high-resolution,
high signal-to-noise spectra of sharp-lined chemically normal stars
including the Sun, and the zero-rotation extremely Cr- and Fe-rich
chemically peculiar star HD 133792. The observed spectrum of the latter
star allowed for comparison with transition probability calculations
based on the orthogonal operator technique with the Cowan code for
Cr II and Fe II lines for lower level energies between 2 eV and
11 eV in the wavelength region 3100 to 9000 Å. In general,
the agreement between the new experimental transition probabilities
and those currently available in VALD2 is fairly good, which helps
to validate the stellar abundance data derived with the VALD2 atomic
parameters. We also found that, for a few important Ti II and Fe II
lines in the visible spectral region, new transition probabilities
are not consistent within their quoted accuracy. In a series
of recent works on experimental f-values for Fe II it was shown that
calculations based on the orthogonal operator technique agree better
with the experimental data than the Cowan code calculations and, hence,
should have preference for stellar spectroscopy. Our analysis of the
Ap star HD 133792 spectrum clearly demonstrates that there are quite
a number of high-excitation Cr II and Fe II lines which are fitted
reasonably well when using the transition probabilities calculated
with the Cowan code. As a rule these lines have their upper energy
levels classified differently in both methods of calculations.

---------------------------------------------------------
Title: The upgrade of HARPS to a full-Stokes high-resolution
spectropolarimeter
Authors: Snik, Frans; Jeffers, Sandra; Keller, Christoph; Piskunov,
Nikolai; Kochukhov, Oleg; Valenti, Jeff; Johns-Krull, Christopher
2008SPIE.7014E..0OS Altcode: 2008SPIE.7014E..22S
We present the design of a compact module that converts the HARPS
instrument at the 3.6-m telescope at La Silla to a full-Stokes
high-resolution spectropolarimeter. The polarimeter will replace the
obsolete Iodine cell inside the HARPS Cassegrain adapter. Utilizing
the two fibers going into the spectrograph, two dual-beam systems
can be positioned in the beam: one with a rotating superachromatic
quarter-wave plate for circular polarimetry and one with a rotating
superachromatic half-wave plate for linear polarimetry. A large
polarimetric precision is ensured by the beam-exchange technique
and a minimal amount of instrumental polarization. The polarimeter,
in combination with the ultra-precise HARPS spectrograph, enables
unprecedented observations of stellar magnetic fields and circumstellar
material without compromising the successful planet-finding program.

---------------------------------------------------------
Title: INTRODUCTION: Nobel Symposium 135: Physics of Planetary Systems
(18 22 June 2007, Lidingö, Stockholm, Sweden)
Authors: Piskunov, Nikolai; Rickman, Hans; Gustafsson, Bengt
2008PhST..130a1001P Altcode:
Since the discovery of the first planet, orbiting a sun-like star
outside of our solar system, astronomy has changed dramatically. This
event inspired a wide spectrum of activities not just in observational
astronomy but in all fields related to planets from star formation to
astrobiology. The discovery itself was the result of long and systematic
work on perfecting measuring techniques and collecting data. Once the
required level of precision was reached news about extrasolar planets
started to appear frequently not just in scientific journals but also in
the general media. Although fast progress is quite obvious in many
areas related to planetary sciences for this Nobel symposium, dedicated
to the Physics of Planetary Systems, we selected five topics where a
number of particularly important breakthroughs happened in the last
decade. These are: detection of exoplanets planet birthplaces:
observations and modelling planet formation evolution of planetary
systems planet characterization. We dedicated a full session,
consisting of a few review talks and a joint discussion, to each of
these topics. The format was a success, but what made this meeting
so remarkable was the quality of the talks. We are very thankful to
the world leading scientists for coming to Lidingö and making this
symposium a truly memorable event. This book contains most of their
contributions for you to enjoy. We are very thankful to the Nobel
Foundation for generous sponsorship which made this symposium possible.

---------------------------------------------------------
Title: Abundance analysis and searching for nonradial pulsations in
the atmosphere of the chemically peculiar star HD 115708
Authors: Semenko, E. A.; Sachkov, M. E.; Ryabchikova, T. A.;
Kudryavtsev, D. O.; Piskunov, N. E.
2008AstL...34..413S Altcode: 2008PAZh...34..455S
We present the results of our abundance analysis for the magnetic
chemically peculiar star HD 115708 based on high-resolution spectra. The
atmospheric chemical composition of HD 115708 ( T eff =
7550 K) is shown to be typical of cool Ap stars with a significant
ionization disequilibrium for the first and second rare earth ions,
which is commonly observed in the atmospheres of pulsating Ap (roAp)
stars. Our study of the vertical distribution of elements has shown
that Mg, Ca, Cr, and Fe concentrate in deeper atmospheric layers, with
their abundances decreasing sharply in the upper layers. The jumps
in abundance are 1.5 3 orders of magnitude. Silicon is distributed
in depth almost uniformly in the atmosphere of HD 115708. The derived
empirical Cr and Fe distributions agree qualitatively with the results
of diffusion calculations. Since the atmospheric chemical peculiarities
in HD 115708 correspond to roAp stars, we have performed a spectroscopic
monitoring to find nonradial pulsations. We have been able to determine
only an upper limit for the amplitude of the possible radial velocity
pulsations, ∼100 m s-1, due to the insufficient temporal
resolution and instability of the main stellar spectrograph (MSS)
of the 6-m telescope.

---------------------------------------------------------
Title: 3D atmospheric structure of the prototypical roAp star HD 24712
(HR1217)
Authors: Lüftinger, T.; Kochukhov, O.; Ryabchikova, T.; Piskunov,
N.; Weiss, W. W.; Ilyin, I.
2008CoSka..38..335L Altcode:
The first analysis of the structure of the surface magnetic field of a
rapidly oscillating Ap (roAp) star is presented. We obtain information
about abundance distributions of a number of chemical elements on the
surface of the prototypical roAp star HD 24712 and about magnetic field
geometry. Inverting rotationally modulated spectra in Stokes parameters
I and V obtained with the SOFIN spectropolarimeter attached to the NOT,
we recover surface abundance structures of sixteen different chemical
elements, including Mg, Ca, Sc, Ti, Cr, Fe, Co, Ni, Y, La, Ce, Pr,
Nd, Gd, Tb, and Dy. Our analysis reveal a pure dipolar structure of
the stellar magnetic field and surprising and unexpected correlations
of the various elemental surface abundance structures to this field
geometry. Stratification analysis at phases of both magnetic extrema
enable us to obtain the vertical dimension in the atmosphere of HD
24712. High time resolved spectroscopic data and observations obtained
with the MOST space photometer give us the possibility to compare
(Lüftinger, 2007) our results to detailed pulsational analysis.

---------------------------------------------------------
Title: Global magnetohydrodynamical models of turbulence in
protoplanetary disks. I. A cylindrical potential on a Cartesian grid
and transport of solids
Authors: Lyra, W.; Johansen, A.; Klahr, H.; Piskunov, N.
2008A&A...479..883L Altcode: 2007arXiv0705.4090L
Aims:We present global 3D MHD simulations of disks of gas and
solids, aiming at developing models that can be used to study various
scenarios of planet formation and planet-disk interaction in turbulent
accretion disks. A second goal is to demonstrate that Cartesian
codes are comparable to cylindrical and spherical ones in handling the
magnetohydrodynamics of the disk simulations while offering advantages,
such as the absence of a grid singularity, for certain applications,
e.g., circumbinary disks and disk-jet simulations. Methods:
We employ the Pencil Code, a 3D high-order finite-difference MHD
code using Cartesian coordinates. We solve the equations of ideal
MHD with a local isothermal equation of state. Planets and stars are
treated as particles evolved with an N-body scheme. Solid boulders are
treated as individual superparticles that couple to the gas through
a drag force that is linear in the local relative velocity between
gas and particle. Results: We find that Cartesian grids are
well-suited for accretion disk problems. The disk-in-a-box models
based on Cartesian grids presented here develop and sustain MHD
turbulence, in good agreement with published results achieved with
cylindrical codes. Models without an inner boundary do not show the
spurious build-up of magnetic pressure and Reynolds stress seen in the
models with boundaries, but the global stresses and alpha viscosities
are similar in the two cases. We investigate the dependence of the
magnetorotational instability on disk scale height, finding evidence
that the turbulence generated by the magnetorotational instability
grows with thermal pressure. The turbulent stresses depend on the
thermal pressure obeying a power law of 0.24 ± 0.03, compatible with
the value of 0.25 found in shearing box calculations. The ratio of
Maxwell to Reynolds stresses decreases with increasing temperature,
dropping from 5 to 1 when the sound speed was raised by a factor 4,
maintaing the same field strength. We also study the dynamics of
solid boulders in the hydromagnetic turbulence, by making use of
106 Lagrangian particles embedded in the Eulerian grid. The
effective diffusion provided by the turbulence prevents settling of
the solids in a infinitesimally thin layer, forming instead a layer
of solids of finite vertical thickness. The measured scale height of
this diffusion-supported layer of solids implies turbulent vertical
diffusion coefficients with globally averaged Schmidt numbers of 1.0 ±
0.2 for a model with α≈10-3 and 0.78 ± 0.06 for a model
with α≈10-1. That is, the vertical turbulent diffusion
acting on the solids phase is comparable to the turbulent viscosity
acting on the gas phase. The average bulk density of solids in the
turbulent flow is quite low (ρp = 6.0×10-11
kg m-3), but in the high pressure regions, significant
overdensities are observed, where the solid-to-gas ratio reached
values as great as 85, corresponding to 4 orders of magnitude higher
than the initial interstellar value of 0.01.

---------------------------------------------------------
Title: Planets in the Galactic Bulge: Results from the SWEEPS Project
Authors: Sahu, K. C.; Casertano, S.; Valenti, J.; Bond, H. E.; Brown,
T. M.; Smith, T. E.; Clarkson, W.; Minniti, D.; Zoccali, M.; Livio,
M.; Renzini, A.; Rich, R. M.; Panagia, N.; Lubow, S.; Brown, T.;
Piskunov, N.
2008ASPC..398...93S Altcode: 2007arXiv0711.4059S
The exoplanets discovered so far have been mostly around relatively
nearby and bright stars. As a result, the host stars are mostly (i)
in the Galactic disk, (ii) relatively massive, and (iii) relatively
metal rich. The aim of the SWEEPS project is to extend our knowledge
to stars which (i) are in a different part of the Galaxy, (ii) have
low masses, and (iii) have a large range of metallicities. To achieve
this goal, we used the Hubble Space Telescope and its Advanced Camera
for Surveys to look for transiting planets around F, G, K, and and M
dwarfs in the Galactic bulge. We photometrically monitored ∼180,000
stars in a dense stellar field in the Galactic bulge continuously for
7 days. We discovered 16 candidate transiting extrasolar planets with
periods of 0.6 to 4.2 days, including a new class of ultra-short period
planets (USPPs) with P&lt;1.2 days. Radial velocity observations of
two brightest candidates support the planetary nature. These results
suggest that planets are equally abundant in the Galactic bulge and
around low-mass stars (within a factor ∼2), and the metallicity
distribution holds even for the stars in the Galactic bulge. The USPPs
occur only around low-mass stars which suggest that close-in planets
around higher-mass stars are either irradiately evaporated, or that
the size of the inner disk hole decreases with decreasing mass of the
host stars.

---------------------------------------------------------
Title: Optimal Extraction of Echelle Spectra
Authors: Piskunov, Nikolai
2008psa..conf..129P Altcode:
The extraction of the echelle spectra registered with a CCD detector
represents a big challenge because of three reasons: (1) the pixel
sampling is often close or worse then optimal, (2) spectral orders are
curved and tilted with respect to the CCD rows (or columns) and (3)
every pixel contains additional noise coming from various sources as
illustrated in Figure 1. The main goal of an optimal extraction is to
recover as much of the science signal while minimizing the contribution
of the noise. Here we present the Slit Function Decomposition algorithm
which replaces the summation in a sliding window with a reconstruction
of the slit illumination profile. The reconstruction is formulated as
an inverse problem solved by iterations and it is robust against most
of the systematic problems including cosmic rays and cosmetic defects.

---------------------------------------------------------
Title: Atomic Diffusion and Mixing in Old Stars. I. Very Large
Telescope FLAMES-UVES Observations of Stars in NGC 6397
Authors: Korn, A. J.; Grundahl, F.; Richard, O.; Mashonkina, L.;
Barklem, P. S.; Collet, R.; Gustafsson, B.; Piskunov, N.
2007ApJ...671..402K Altcode: 2007arXiv0709.0639K
We present a homogeneous photometric and spectroscopic analysis of
18 stars along the evolutionary sequence of the metal-poor globular
cluster NGC 6397 ([Fe/H]~-2), from the main-sequence turnoff point to
red giants below the bump. The spectroscopic stellar parameters, in
particular stellar parameter differences between groups of stars, are
in good agreement with broadband and Strömgren photometry calibrated
on the infrared flux method. The spectroscopic abundance analysis
reveals, for the first time, systematic trends of iron abundance
with evolutionary stage. Iron is found to be 30% less abundant in the
turnoff point stars than in the red giants. An abundance difference
in lithium is seen between the turnoff point and warm subgiant
stars. The impact of potential systematic errors on these abundance
trends (stellar parameters, the hydrostatic and LTE approximations)
is quantitatively evaluated and found not to alter our conclusions
significantly. Trends for various elements (Li, Mg, Ca, Ti, and Fe)
are compared with stellar structure models including the effects of
atomic diffusion and radiative acceleration. Such models are found
to describe the observed element-specific trends well, if extra
(turbulent) mixing just below the convection zone is introduced. It
is concluded that atomic diffusion and turbulent mixing are largely
responsible for the subprimordial stellar lithium abundances of warm
halo stars. Other consequences of atomic diffusion in old metal-poor
stars are also discussed. Based on observations carried out at
the European Southern Observatory (ESO), Paranal, Chile, under program
ID 075.D-0125(A).

---------------------------------------------------------
Title: Weather in stellar atmosphere revealed by the dynamics of
mercury clouds in α Andromedae
Authors: Kochukhov, Oleg; Adelman, Saul J.; Gulliver, Austin F.;
Piskunov, Nikolai
2007NatPh...3..526K Altcode: 2007arXiv0705.4469K
The formation of long-lasting structures at the surfaces of stars
is commonly ascribed to the action of strong magnetic fields. This
paradigm is supported by observations of evolving cool spots in the
Sun and active late-type stars, and stationary chemical spots in the
early-type magnetic stars. However, results of our seven-year monitoring
of mercury spots in non-magnetic early-type star α Andromedae show that
the picture of magnetically driven structure formation is fundamentally
incomplete. Using an indirect stellar-surface mapping technique, we
construct a series of two-dimensional images of starspots and discover
a secular evolution of the mercury cloud cover in this star. This
remarkable structure-formation process, observed for the first time
in any star, is plausibly attributed to a non-equilibrium, dynamical
evolution of the heavy-element clouds created by atomic diffusion,
and may have the same underlying physics as the weather patterns on
terrestrial and giant planets.

---------------------------------------------------------
Title: 3-D hydrodynamic simulations of convection in A stars
Authors: Kochukhov, O.; Freytag, B.; Piskunov, N.; Steffen, M.
2007IAUS..239...68K Altcode: 2006astro.ph.10111K
Broadening and asymmetry of spectral lines in slowly rotating late
A-type stars provide evidence for high-amplitude convective motions. The
properties of turbulence observed in the A-star atmospheres are not
understood theoretically and contradict results of previous numerical
simulations of convection. Here we describe an ongoing effort to
understand the puzzling convection signatures of A stars with the
help of 3-D hydrodynamic simulations. Our approach combines realistic
spectrum synthesis and non-grey hydrodynamic models computed with the
CO5BOLD code. We discuss these theoretical predictions and confront
them with high-resolution spectra of A stars. Our models have, for
the first time, succeeded in reproducing the observed profiles of weak
spectral lines without introducing fudge broadening parameters.

---------------------------------------------------------
Title: Search for the radial magnetic-field gradient in the CP star
α 2 CVn
Authors: Romanyuk, I. I.; Panchuk, V. E.; Piskunov, N. E.; Kudryavtsev,
D. O.
2007AstBu..62...26R Altcode:
The possibility of investigating the vertical structure of the
magnetic field in chemically peculiar main-sequence stars is
discussed. The nonuniform distribution of chemical elements over
the surface complicates the problem substantially. The most efficient
measurements are shown to be those of the longitudinal field components
based on spectral lines with wavelengths longer and shorter than
3646 Å (shortward and longward of the Balmer jump), which form at
different optical depths in the atmosphere. Various methodological
problems are addressed that must be overcome in order to accomplish
the task. The brightest magnetic star α 2 CVn is observed
with the echelle spectrometer equipped with an Uppsala CCD chip. New
observations corroborate our previous result: the longitudinal component
of the magnetic field B e of the α 2 CVn star
increases with depth by about 30% over the atmosphere thickness scale.

---------------------------------------------------------
Title: Commission 29: Stellar Spectra
Authors: Sneden, Christopher; Parthasarathy, M.; Castelli, Fiorella;
Cunha, Katia; Eenens, Philippe; Friel, Eileen; Gratton, Raffaele;
Hubeny, Ivan; Landstreet, John D.; Mathys, Gautier; Piskunov, Nikolai;
Primas, Francesca; Takada-Hidai, Masahide; Weiss, Werner
2007IAUTA..26..203S Altcode:
Participants in Commission 29 study various aspects of stellar spectra
and the information that can be extracted from spectra. The list
of fields of interest of the Organizing Committee members suggest
some major current research topics in this area are stellar chemical
compositions and surface/envelope phenomena. Some of the topics of this
commission have overlap with other commissions, such as Commission
14 (Atomic and Molecular Data), 26 (Double and Multiple Stars),
27 (Variable Stars), 30 (Radial Velocities), 36 (Theory of Stellar
Atmospheres), and 37 (Star Clusters and Associations). Many Commission
29 members are also members of these other commissions.

---------------------------------------------------------
Title: Transiting extrasolar planetary candidates in the Galactic
bulge
Authors: Sahu, Kailash C.; Casertano, Stefano; Bond, Howard E.;
Valenti, Jeff; Ed Smith, T.; Minniti, Dante; Zoccali, Manuela;
Livio, Mario; Panagia, Nino; Piskunov, Nikolai; Brown, Thomas M.;
Brown, Timothy; Renzini, Alvio; Rich, R. Michael; Clarkson, Will;
Lubow, Stephen
2006Natur.443..534S Altcode: 2006astro.ph.10098S
More than 200 extrasolar planets have been discovered around relatively
nearby stars, primarily through the Doppler line shifts owing to reflex
motions of their host stars, and more recently through transits of
some planets across the faces of the host stars. The detection of
planets with the shortest known periods, 1.2-2.5 days, has mainly
resulted from transit surveys which have generally targeted stars
more massive than 0.75Msolar, where Msolar
is the mass of the Sun. Here we report the results from a planetary
transit search performed in a rich stellar field towards the Galactic
bulge. We discovered 16 candidates with orbital periods between
0.4 and 4.2 days, five of which orbit stars of masses in the range
0.44-0.75Msolar. In two cases, radial-velocity measurements
support the planetary nature of the companions. Five candidates
have orbital periods below 1.0 day, constituting a new class of
ultra-short-period planets, which occur only around stars of less than
0.88Msolar. This indicates that those orbiting very close
to more-luminous stars might be evaporatively destroyed or that jovian
planets around stars of lower mass might migrate to smaller radii.

---------------------------------------------------------
Title: New Abundances for Old Stars - Atomic Diffusion at Work in
NGC 6397
Authors: Korn, A.; Grundahl, F.; Richard, O.; Barklem, P.; Mashonkina,
L.; Collet, R.; Piskunov, N.; Gustafsson, B.
2006Msngr.125....6K Altcode: 2006astro.ph.10077K; 2006Msngr.125...10K
A homogeneous spectroscopic analysis of unevolved and evolved
stars in the metal-poor globular cluster NGC 6397 with FLAMES-UVES
reveals systematic trends of stellar surface abundances that are
likely caused by atomic diffusion. This finding helps to understand,
among other issues, why the lithium abundances of old halo stars are
significantly lower than the abundance found to be produced shortly
after the Big Bang.

---------------------------------------------------------
Title: A probable stellar solution to the cosmological lithium
discrepancy
Authors: Korn, A. J.; Grundahl, F.; Richard, O.; Barklem, P. S.;
Mashonkina, L.; Collet, R.; Piskunov, N.; Gustafsson, B.
2006Natur.442..657K Altcode: 2006astro.ph..8201K
The measurement of the cosmic microwave background has strongly
constrained the cosmological parameters of the Universe. When the
measured density of baryons (ordinary matter) is combined with
standard Big Bang nucleosynthesis calculations, the amounts of
hydrogen, helium and lithium produced shortly after the Big Bang can
be predicted with unprecedented precision. The predicted primordial
lithium abundance is a factor of two to three higher than the value
measured in the atmospheres of old stars. With estimated errors of 10
to 25%, this cosmological lithium discrepancy seriously challenges
our understanding of stellar physics, Big Bang nucleosynthesis or
both. Certain modifications to nucleosynthesis have been proposed,
but found experimentally not to be viable. Diffusion theory, however,
predicts atmospheric abundances of stars to vary with time, which offers
a possible explanation of the discrepancy. Here we report spectroscopic
observations of stars in the metal-poor globular cluster NGC6397
that reveal trends of atmospheric abundance with evolutionary stage
for various elements. These element-specific trends are reproduced
by stellar-evolution models with diffusion and turbulent mixing. We
thus conclude that diffusion is predominantly responsible for the low
apparent stellar lithium abundance in the atmospheres of old stars by
transporting the lithium deep into the star.

---------------------------------------------------------
Title: Magnetic Doppler Imaging of Active Stars
Authors: Kochukhov, O.; Piskunov, N.
2006IAUJD...8E...7K Altcode:
Rotational modulation of the intensity and polarization spectra
of magnetic stars offers a unique possibility to reconstruct the
structure of surface magnetic fields and investigate their relation to
the temperature and chemical spots in stellar atmospheres. The complex
task of obtaining self-consistent and accurate maps of photospheric
magnetic fields can finally be addressed with the Magnetic Doppler
imaging technique. We present the new version of our magnetic Doppler
imaging code which aims at temperature and magnetic mapping of cool
active stars. Our magnetic imaging procedure is unique in its capability
to model individual spectral features in several Stokes parameters
simultaneously. We discuss performance and intrinsic limitations of
our magnetic Doppler imaging method. A special emphasis is given to the
mapping using both atomic and molecular spectral lines. The latter may,
for the first time, give us a tool to learn about magnetic fields in
the interior of starspots.

---------------------------------------------------------
Title: Global 3-D solar-type star-disc dynamo systems: I. MHD modeling
Authors: von Rekowski, B.; Piskunov, N.
2006AN....327..340V Altcode:
We have carried out global three-dimensional magnetohydrodynamic
simulations of the star-disc interaction region around a young
solar-type star. The magnetic field is generated and maintained
by dynamos in the star as well as in the disc. The developing mass
flows possess non-periodic time-variable azimuthal structure and are
controlled by the nonaxisymmetric magnetic fields. Since the stellar
field drives a strong stellar wind, accretion is anti-correlated with
the stellar field strength and disc matter is spiraling onto the star at
low latitudes, both contrary to the generally assumed accretion picture.

---------------------------------------------------------
Title: Pinning Down Gravitational Settling
Authors: Korn, A. J.; Piskunov, N.; Grundahl, F.; Barklem, P.;
Gustafsson, B.
2006cams.book..294K Altcode: 2006astro.ph..8338K
We analyse high-resolution archival UVES data of turnoff
and subgiant stars in the nearby globular cluster NGC6397
([Fe/H]≈-2). Balmer-profile analyses are performed to derive
reddening-free effective temperatures. Due to the limited S/N and
uncertainties related to blaze removal, we find the data quality
insufficient to exclude the existence of gravitational settling. If
the newly derived effective temperatures are taken as a basis for an
abundance analysis, the photospheric iron (Fe ii) abundance in the
turnoff stars is 0.11 dex lower than in the (well-mixed) subgiants.

---------------------------------------------------------
Title: Inhomogeneous distribution of mercury on the surfaces of
rapidly rotating HgMn stars
Authors: Kochukhov, O.; Piskunov, N.; Sachkov, M.; Kudryavtsev, D.
2005A&A...439.1093K Altcode: 2005astro.ph..5124K
Starspots are usually associated with the action of magnetic fields
at stellar surfaces. However, an inhomogeneous chemical distribution
of mercury was found recently for the mercury-manganese (HgMn) star
α And - a well-established member of a non-magnetic subclass of the
chemically peculiar stars of the upper main sequence. In this study
we present first results of the high-resolution survey of the Hg
II 3984 Å resonance line in the spectra of rapidly rotating HgMn
stars with atmospheric parameters similar to those of α And. We
use spectrum synthesis modelling and take advantage of the Doppler
resolution of stellar surfaces to probe the horizontal structure of
mercury distribution. Clear signatures of spots are found in the Hg
II 3984 Å line profiles of HR 1185 and HR 8723. Two observations of
the latter star separated by two days give evidence for line profile
variability. We conclude that inhomogeneous distribution of Hg is
a common phenomenon for the rapidly rotating HgMn stars in the 13
000-13 800 K effective temperature range independent of the stellar
evolutionary stage. These results establish the existence of a new class
of spectrum variable spotted B-type stars. It is suggested that the
observed Hg inhomogeneities arise from dynamical instabilities in the
chemical diffusion processes and are unrelated to magnetic phenomena.

---------------------------------------------------------
Title: Cool stars in the Gaia photometric system
Authors: Heiter, U.; Piskunov, N.; Gustafsson, B.; Jordi, C.; Carrasco,
J. M.
2005ESASP.560..635H Altcode: 2005csss...13..635H
No abstract at ADS

---------------------------------------------------------
Title: Magnetic Doppler Imaging: Mathematical Basis
Authors: Piskunov, N.
2005EAS....17..245P Altcode:
We address important mathematical properties of solutions of the
Magnetic Doppler Imaging problem. We show that the underlying inverse
problem based on all 4 Stokes parameters is well-posed and thus has
a unique solution. The only purpose of regularization is to suppress
instabilities induced by sparse sampling of phase and/or wavelength
when dealing with practical data. Therefore, the final solution is
stable with respect to the initial guess and is not affected by the
selection of a specific type of regularization.

---------------------------------------------------------
Title: Magnetic Fields and Stellar Surface Structures
Authors: Piskunov, Nikolai
2005hris.conf..315P Altcode:
We discuss the use of high-resolution spectroscopy for studying
inhomogeneities on stellar surfaces. Examples of such inhomogeneities
include chemical and temperature spots, pulsation waves and magnetic
fields. Presence of surface structures reflects important physical
processes occurring in much deeper layers than can be observed and,
therefore, they contain valuable information for theoretical modelling
of stars.

---------------------------------------------------------
Title: Panel discussion section B
Authors: Piskunov, N.
2004IAUS..224..115P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Multi-element abundance Doppler imaging of the rapidly
oscillating Ap star HR 3831
Authors: Kochukhov, O.; Drake, N. A.; Piskunov, N.; de la Reza, R.
2004A&A...424..935K Altcode:
We investigate magnetic field geometry and surface distribution of
chemical elements in the rapidly oscillating Ap star HR 3831. Results
of the model atmosphere analysis of the spectra of this star are
combined with the Hipparcos parallax and evolutionary models to
obtain new accurate estimates of the fundamental stellar parameters:
Teffv{7650}, log L/L⊙=1.09, M/M⊙=
1.77 and an inclination angle i=68° of the stellar axis of rotation. We
find that the variation of the longitudinal magnetic field of HR
3831 and the results of our analysis of the magnetic intensification
of Fe I lines in the spectrum of this star are consistent with a
dipolar magnetic topology with a magnetic obliquity β=87° and
a polar strength Bp=2.5 kG. We apply a multi-element
abundance Doppler imaging inversion code for the analysis of the
spectrum variability of HR 3831, and recover surface distributions
of 17 chemical elements, including Li, C, O, Na, Mg, Si, Ca, Ti, Cr,
Mn, Fe, Co, Ba, Y, Pr, Nd, Eu. Our study represents the most thorough
examination of the surface chemical structure in a magnetic Ap star and
provides important observational constraints for modelling radiative
diffusion in magnetic stars. The exceedingly high quality of some of
our spectroscopic data allowed us to reconstruct unprecedented details
of abundance distributions, demonstrating a high level of complexity
in the surface structure down to the resolution limit of the Doppler
maps. The Doppler imaging analysis of HR 3831 forms a basis for
subsequent detailed observational investigations and theoretical
modelling of non-radial oscillations in this star. We discuss the
compound effect of the chemical nonuniformities and pulsational
velocity field on the rapid line profile variations, and assess the
possibility of identifying pulsation modes by using spatial filtering
produced by an inhomogeneous abundance distribution. The results of
our study of the surface chemical structure suggest that differences
in pulsational behaviour of lines of different ions observed for HR
3831 are not a consequence of horizontal atmospheric inhomogeneities,
but predominantly a depth effect. Based on observations obtained
at the European Southern Observatory, La Silla, Chile.

---------------------------------------------------------
Title: The influence of magnetic fields on the hydrostatic structure
of the atmospheres of chemically peculiar stars
Authors: Valyavin, G.; Kochukhov, O.; Piskunov, N.
2004A&A...420..993V Altcode:
We discuss the properties of atmospheres of chemically peculiar magnetic
stars. The slow evolution of global magnetic fields leads to the
development of an induced electric current in all conductive atmospheric
layers. The Lorentz force, which results from the interaction between
a magnetic field and the induced current, may change the atmospheric
structure and provide insight into the formation and evolution of
stellar magnetic fields. We developed a model atmosphere code that
takes into account the Lorentz force in the equation of hydrostatic
equilibrium, and computed a number of model atmospheres for magnetic A
and B stars. The surface distribution of a magnetic field was assumed
to be a dipole, slightly distorted by the induced atmospheric electric
current. The interaction between the magnetic field and electric current
is modelled in detail, taking into account microscopic properties
of the stellar plasma. The presence of a significant Lorentz force
leads to substantial modification of the atmospheric structure and
in particular the pressure stratification, which in turn influences
the formation of absorption spectral features, especially hydrogen
Balmer lines. Furthermore, we find that rotational modulation of the
disk-average parameters of a global stellar magnetic field causes
characteristic rotational variability of hydrogen lines. With our
model, observable effects correspond to induced electric currents of
the order of 10-11 cgs, which requires characteristic field
evolution times 2-3 orders of magnitude shorter than the field decay
time estimated for magnetic A and B stars assuming fossil dipolar field
topology in the stellar interior. Using the computations of our model
atmospheres we consider an observational aspect of the problem and
attempt to interpret photometric data on the variability of hydrogen
lines within the framework of simplest model of the evolution of global
magnetic fields. With the hydrogen line data we find tentative support
for the presence of a non-negligible Lorentz force in the atmospheres
of some magnetic chemically peculiar stars.

---------------------------------------------------------
Title: Near-Polar Starspots and Polar Dynamo Waves
Authors: Novikov, S. V.; Piskunov, N. E.; Sokoloff, D. D.
2004ARep...48..522N Altcode:
A possible mechanism for the formation of near-polar magnetic spots on
some stars with convective envelopes is proposed. The mechanism is based
on the idea that the maximum of the dynamo waves that are excited in
thin convective shells by the dynamo mechanism is shifted appreciably
from the maximum of the magnetic-field sources in the direction of
motion of the dynamo wave. If there is no region of super-rotation
near the equator for some reason (as a consequence of disruption due
to tidal interaction with a companion in a binary system, for example)
and the wave of stellar activity propagates toward the poles rather
than toward the equator, this maximum will be in the near-polar regions.

---------------------------------------------------------
Title: No magnetic field variation with pulsation phase in the roAp
star γ Equulei
Authors: Kochukhov, O.; Ryabchikova, T.; Piskunov, N.
2004A&A...415L..13K Altcode: 2004astro.ph..1048K
We present an analysis of 210 high-resolution time-resolved
spectropolarimetric observations of the roAp star γ Equ obtained over
three nights in August and September 2003. Radial velocity variations
due to p-mode non-radial pulsations are clearly detected in the lines
of rare-earth elements, in particular Pr III, Nd II and Nd III. In
contrast, we find absolutely no evidence for the variation of the mean
longitudinal magnetic field over the pulsation period in γ Equ at the
level of 110-240 G which was recently reported by Leone &amp; Kurtz
(\cite{LK03}). Our investigation of the variability of circularly
polarized profiles of 13 Nd III lines demonstrates that, at the 3σ
confidence level, no magnetic field variation with an amplitude above
≈40-60 G was present in γ Equ during our monitoring of this star.

---------------------------------------------------------
Title: Magnetic Doppler imaging of 53 Camelopardalis in all four
Stokes parameters
Authors: Kochukhov, O.; Bagnulo, S.; Wade, G. A.; Sangalli, L.;
Piskunov, N.; Landstreet, J. D.; Petit, P.; Sigut, T. A. A.
2004A&A...414..613K Altcode:
We present the first investigation of the structure of the
stellar surface magnetic field using line profiles in all four
Stokes parameters. We extract the information about the magnetic
field geometry and abundance distributions of the chemically
peculiar star 53 Cam by modelling time-series of high-resolution
spectropolarimetric observations with the help of a new magnetic
Doppler imaging code. This combination of the unique four Stokes
parameter data and state-of-the-art magnetic imaging technique makes it
possible to infer the stellar magnetic field topology directly from the
rotational variability of the Stokes spectra. In the magnetic imaging
of 53 Cam we discard the traditional multipolar assumptions about
the structure of magnetic fields in Ap stars and explore the stellar
magnetic topology without introducing any global a priori constraints
on the field structure. The complex magnetic model of 53 Cam derived
with our magnetic Doppler imaging method achieves a good fit to the
observed intensity, circular and linear polarization profiles of strong
magnetically sensitive Fe II spectral lines. Such an agreement between
observations and model predictions was not possible with any earlier
multipolar magnetic models, based on modelling Stokes I spectra and
fitting surface averaged magnetic observables (e.g., longitudinal field,
magnetic field modulus, etc.). Furthermore, we demonstrate that even
the direct inversion of the four Stokes parameters of 53 Cam assuming
a low-order multipolar magnetic geometry is incapable of achieving
an adequate fit to our spectropolarimetric observations. Thus, as a
main result of our investigation, we discover that the magnetic field
topology of 53 Cam is considerably more complex than any low-order
multipolar expansion, raising a general question about the validity of
the multipolar assumption in the studies of magnetic field structures
of Ap stars. In addition to the analysis of the magnetic field of 53
Cam, we reconstruct surface abundance distributions of Si, Ca, Ti, Fe
and Nd. These abundance maps confirm results of the previous studies
of 53 Cam, in particular dramatic antiphase variation of Ca and Ti
abundances. Based on observations obtained with the Bernard Lyot
telescope of the Pic du Midi Observatory and Isaac Newton Telescope
of the La Palma Observatory.

---------------------------------------------------------
Title: He and Si surface inhomogeneities of four Bp variable stars
Authors: Briquet, M.; Aerts, C.; Lüftinger, T.; De Cat, P.; Piskunov,
N. E.; Scuflaire, R.
2004A&A...413..273B Altcode:
We present ground-based multi-colour Geneva photometry and
high-resolution spectra of four variable B-type stars: HD 105382, HD
131120, HD 138769 and HD 55522. All sets of data reveal monoperiodic
stars. A comparison of moment variations of two spectral lines, one
silicon line and one helium line, allows us to exclude the pulsation
model as being the cause of the observed variability of the four
stars. We therefore delete the four stars from the list of candidate
slowly pulsating B stars. We attribute the line-profile variations to
non-homogeneous distributions of elements on the stellar surface and we
derive abundance maps for both elements on the stellar surface by means
of the Doppler Imaging technique. We confirm HD 131120 to be a He-weak
star and we classify HD 105382, HD 138769 as new He-weak stars. HD 55522
has the solar helium abundance but the mean abundance value of He varies
by 0.8 dex during the stellar rotation. For HD 131120 and HD 105382,
helium is enhanced in regions of the stellar surface where silicon is
depleted and depleted in regions where silicon is enhanced. Based
on observations obtained with the Swiss photometric telescope and ESO's
CAT/CES telescope, both situated at La Silla, Chile. Appendix A,
Tables 1 and 2 and Figs. 9, 11, 13 are only available in electronic
form at http://www.edpsciences.org

---------------------------------------------------------
Title: Balmer Lines and Effective Temperatures in Cool Stars
Authors: Barklem, P. S.; Stempels, H. C.; Kochukhov, O.; Piskunov,
N.; O'Mara, B. J.
2003csss...12.1103B Altcode:
Theoretical work on the self-broadening of Balmer lines by us predicts
a large impact on model profiles, and therefore effective temperature
determinations, particularly in metal-poor stars. We present initial
results of the application to observations of a sample of cool dwarf
stars. The effective temperatures determined for our sample show
much improved agreement with the infra-red flux method results in the
literature when compared with analysis using the previously available
broadening theory.

---------------------------------------------------------
Title: Probing Magnetospheric Infall onto CTTS with Time-resolved
Veiling Measurements.
Authors: Stempels, H. C.; Piskunov, N.
2003csss...12..735S Altcode:
We show that time-resolved veiling measurements over a large wavelength
range can probe individual accretion events onto Classical T Tauri
Stars (CTTS). We demonstrate two methods of measuring veiling. Using
these measurements, we model CTTS spectra as a superposition of two
components representing stellar and accretion emission. The simple
but functional method allows us to estimate the temperature of the
accretion shock and the relative surface area of the accretion regions
on the star. We apply this method to a series of spectra of the CTTS
RU Lupi and present our first results.

---------------------------------------------------------
Title: The photosphere and veiling spectrum of T Tauri stars
Authors: Stempels, H. C.; Piskunov, N.
2003A&A...408..693S Altcode:
Using recent high signal-to-noise and high spectral resolution (R ~ 60
000) observations with VLT/UVES, we have analysed the photosphere and
veiling spectrum of five T Tauri stars. With a grid of 1-dimensional
plane-parallel hydrostatic model atmospheres from the MARCS consortium
we have determined their atmospheric properties, calculated synthetic
spectra and determined the spectrum of the veiling continuum. Our
analysis of the veiling spectrum supports the view that veiling
can be represented by a combination of continuum sources. However,
for the most strongly accreting stars we find a broad region around
5300 Å where the derived level of veiling is consistently higher than
expected from continuum sources. Based on observations collected
at the European Southern Observatory, Chile (proposal 65.I-0404).

---------------------------------------------------------
Title: Doppler Imaging of the Ap star epsilon Ursae Majoris: Ca,
Cr, Fe, Mg, Mn, Ti, Sr
Authors: Lueftinger, T.; Kuschnig, R.; Piskunov, N. E.; Weiss, W. W.
2003A&A...406.1033L Altcode:
The surface abundance structure of seven elements of the brightest
chemically peculiar A-type star, epsilon Ursae Majoris (epsilon UMa,
HD 112185, HR 4905) has been determined. Cr, Fe and, Mn are enhanced at
the magnetic polar region of epsilon UMa while they avoid the magnetic
equator. Sr seems to behave like Cr, Fe, and Mn, but is concentrated
only at one of the two magnetic poles. Ti, in contrast, is accumulated
at the magnetic equator and is depleted where Cr and Fe are accumulated,
in accordance with theoretical predictions. Mg and Ca do not correlate
with the distribution of Cr, Fe, Mn, and Sr or with Ti. The surface
distribution of Mn, Sr, Ti, and Mg was determined for the first time
for this star. A Doppler Imaging code was used that allows to analyse
elements present in complex spectral line blends and thus to increase
significantly the potential to map more elements. We compare our Cr
and Fe distributions to already published maps. The high consistency
of our results, based on different observations and Doppler Imaging
codes, proves the reliability of the different methods.

---------------------------------------------------------
Title: PEPSI spectro-polarimeter for the LBT
Authors: Strassmeier, Klaus G.; Hofmann, Axel; Woche, Manfred F.; Rice,
John B.; Keller, Christoph U.; Piskunov, N. E.; Pallavicini, Roberto
2003SPIE.4843..180S Altcode:
PEPSI (Postham Echelle Polarimetric and Spectroscopic Instrument) is
to use the unique feature of the LBT and its powerful double mirror
configuration to provide high and extremely high spectral resolution
full-Stokes four-vector spectra in the wavelength range 450-1100nm. For
the given aperture of 8.4m in single mirror mode and 11.8m in double
mirror mode, and at a spectral resolution of 40,000-300,000 as designed
for the fiber-fed Echelle spectrograph, a polarimetric accuracy between
10-4 and 10-2 can be reached for targets with
visual magnitudes of up to 17th magnitude. A polarimetric accuracy
better than 10-4 can only be reached for either targets
brighter than approximately 10th magnitude together wiht a substantial
trade-off wiht the spectral resolution or with spectrum deconvolution
techniques. At 10-2, however, we will be able to observe
the brightest AGNs down to 17th magnitude.

---------------------------------------------------------
Title: Round Table Summary: Radiative Transfer Problems
Authors: Piskunov, N.
2003IAUS..210..107P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Doppler and Zeeman Doppler Imaging of roAp Stars
Authors: Lueftinger, T.; Ryabchikova, T. A.; Weiss, W. W.; Khochukhov,
O.; Piskunov, N. E.; Kuschnig, R.; Wade, G. A.
2003ASPC..305...92L Altcode: 2003mfob.conf...92L
No abstract at ADS

---------------------------------------------------------
Title: Modelling of Stellar Atmospheres
Authors: Piskunov, N.; Weiss, W. W.; Gray, D. F.
2003IAUS..210.....P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Magnetic Doppler Imaging of Chemically Peculiar Stars
Authors: Kochukhov, O.; Piskunov, N.; Bagnulo, S.; Landstreet, J. D.;
Sigut, T. A. A.; Petit, P.; Wade, G. A.
2003ASPC..307..549K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Parametric Resonance and Magnetic Activity in Close Binary
Systems
Authors: Sokoloff, D.; Piskunov, N.
2003IAUS..210P.E43S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Hydrogen Balmer Lines as Probes of Stellar Atmospheres
Authors: Barklem, P. S.; Piskunov, N.
2003IAUS..210P.E28B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Magnetic Doppler Imaging of Early-Type Stars
Authors: Piskunov, N. E.; Kochukhov, O.
2003ASPC..305...83P Altcode: 2003mfob.conf...83P
No abstract at ADS

---------------------------------------------------------
Title: The Influence of the Global Magnetic Field Evolution on the
Structure of Atmospheres of Early-Type Stars
Authors: Valyavin, G.; Kochukhov, O.; Piskunov, N.
2003IAUS..210P.A14V Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Magnetic Doppler Imaging of Solar-type Stars
Authors: Piskunov, N.; Kochukhov, O.
2003ASPC..307..539P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Tools and Methods for Abundance Analysis
Authors: Knoglinger, P.; Nesvacil, N.; Kupka, F.; Mittermayer, P.;
Piskunov, N.; Weiss, W. W.; Bruntt, H.
2003IAUS..210P.E66K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Nonaxisymmetric cool spot distributions and dynamo action in
close binaries
Authors: Moss, D.; Piskunov, N.; Sokoloff, D.
2002A&A...396..885M Altcode:
We investigate the nonaxisymmetric magnetic field distribution in the
components of close binary systems, generated by a stellar dynamo with a
nonaxisymmetric distribution of the alpha -coefficient, proportional to
the mean helicity of the convective motions in the stellar convective
envelope. The nonaxisymmetry of alpha is assumed to be connected with
interaction with the binary companion, i.e. the reflection effect and
tidal interaction. The degree of asymmetry is estimated from the known
parameters of ER Vulpeculae, an active RS CVn-type star. We demonstrate
that the synchronization of rotation and orbital motion of ER Vulpeculae
due to tidal interaction is sufficient to allow nonaxisymmetric magnetic
structures to survive in the presence of smoothing by differential
rotation. The dynamo driven nonaxisymmetric magnetic structures
are usually steady in the reference frame connected with the alpha
-spot. However, we found a resonant excitation of an oscillatory,
strongly nonaxisymmetric, configuration, driven by the joint action of
the alpha -effect and differential rotation. The magnetic structures
obtained are predominantly manifested on the stellar surface in
the form of spots of radial magnetic field. Their form and size are
similar to the form and size of cool spots observed on the surfaces
of both components of ER Vulpeculae, and their displacements from the
alpha -spots are comparable to that of the observed cool spots from
the hot spots connected with the reflection effect. Possible relevant
observations are discussed.

---------------------------------------------------------
Title: Spectroscopy of T Tauri stars with UVES. Observations and
analysis of RU Lup
Authors: Stempels, H. C.; Piskunov, N.
2002A&A...391..595S Altcode:
We present the first results of our observations of classical T
Tauri Stars with UVES/VLT. The data consists of high signal-to-noise
(ge 150) and high spectral resolution (R ~ 60 000) spectra. A large
simultaneous wavelength coverage throughout most of the visible spectrum
and comparatively short integration times allow us to study variability
on short time-scales, using a number of diagnostics reflecting a
wide range of physical processes. In particular we concentrate on
the properties and geometry of the accretion process in the strongly
accreting and highly variable CTTS RU Lup. We use the evolution of
the level of veiling, the shapes of absorption and emission lines, and
correlations between these diagnostics, to make new measurements of the
fundamental stellar parameters as well as constraints on the accretion
process and its geometry. We also derive the shortest time-scale
of incoherent changes, which has implications for the nature of the
accretion process in RU Lup. Based on observations collected at the
European Southern Observatory, Chile (proposal 65.I-0404).

---------------------------------------------------------
Title: Swing excitation and magnetic activity in close binary systems
Authors: Sokoloff, D.; Piskunov, N.
2002MNRAS.334..925S Altcode:
Parametric resonance between the perturbation of a stellar
convective zone affected by a companion of a close binary system and
non-axisymmetric dynamo modes can play an important role in close
binary systems. This process in combination with the previously
suggested α2-mechanism is probably responsible for
strongly non-axisymmetric magnetic activity observed in several close
binaries. The conditions required for swing excitation to occur in such
systems are directly related to the status of rotational synchronization
between the orbital motion and rotation of the star, which can be
used as a tool to discover such objects. One potential candidate -
an active RS CVn-type star ER Vulpeculae - shows indications of the
swing excitation.

---------------------------------------------------------
Title: Doppler Imaging of stellar magnetic fields. III. Abundance
distribution and magnetic field geometry of alpha 2 CVn
Authors: Kochukhov, O.; Piskunov, N.; Ilyin, I.; Ilyina, S.;
Tuominen, I.
2002A&A...389..420K Altcode:
We used the new magnetic Doppler Imaging code to reconstruct the
magnetic field geometry and surface abundance distributions for the
classical magnetic CP star alpha 2 CVn. High-resolution
spectropolarimetric observations in the Stokes I and V parameters were
collected with the SOFIN échelle spectrograph at the Nordic Optical
Telescope. This superb observational material in combination with the
advanced modelling technique allowed to achieve the first simultaneous
self-consistent mapping of the vector magnetic field and the abundance
distributions of six chemical elements. In recovering the stellar
magnetic distribution no prior assumptions about the field geometry
or strength were made. Instead, we restricted possible solutions of
the inverse problem by means of the multipolar regularization method
which searches for the field map close to a general non-axisymmetric
multipolar configuration but allows departures from this geometry if
that is required by the observational data. We found that the magnetic
field of alpha 2 CVn/ is dominated by a dipolar component
and has a minor quadrupole contribution. The surface distributions of
the chemical species form symmetric patterns which closely follow the
magnetic geometry. This discovery constitutes one of the first direct
observational constraints on the horizontal diffusion processes acting
in the upper envelope of a strongly magnetized stellar atmosphere. In
addition to the extensive magnetic Doppler Imaging analysis, we derived
new accurate estimates of the atmospheric parameters and basic physical
properties of alpha 2 CVn/ using the energy distribution,
hydrogen line profiles and the recent Hipparchos parallax. Based on
observations obtained with the Nordic Optical Telescope (NOT) and
Isaac Newton Telescope (INT), La Palma, Spain.

---------------------------------------------------------
Title: Spectropolarimetry of starspots
Authors: Piskunov, N.
2002AN....323..257P Altcode:
We use the simulations of Stokes profiles for active late-type stars in
order to assess the requirements to the observations and select the best
observing strategy for these objects. The synthetic spectropolarimetry
was computed using models of magnetic fields distribution for several
rotational phases throughout the activity cycle. The simulations show
that cyclic variations of the polarization profiles are more systematic
and easier to observe and that averaging over single rotation periods
may be used to increase the signal-to-noise ratio.

---------------------------------------------------------
Title: Doppler Imaging of stellar magnetic fields. II. Numerical
experiments
Authors: Kochukhov, O.; Piskunov, N.
2002A&A...388..868K Altcode:
We present numerical experiments designed to evaluate the performance
of the new Magnetic Doppler Imaging (MDI) code INVERS10. Numerous test
runs demonstrate what can be achieved with the MDI method and allow
assessment of the systematic errors that can cause distortions of the
maps. Our numerical experiments showed that given high-resolution
observations in four Stokes parameters the code is capable of
reconstructing abundance and magnetic field vector distributions
simultaneously and without any prior assumptions about the magnetic
field geometry. At the same time we found that in order to achieve
reliable reconstruction using only circular polarization data it is
necessary to impose additional constraints on the possible structure of
the magnetic field. Numerical tests also reveal surprisingly different
properties of the MDI maps from conventional scalar maps which we
attribute to the complex relation between the orientation of the field
and the polarization signal. We conclude that the information about the
field is primarily extracted from the changes in magnetic orientation
due to rotation rather than from the Doppler shifts critical for scalar
Doppler Imaging maps making it possible to apply the MDI to even very
slow rotators.

---------------------------------------------------------
Title: New algorithms for reducing cross-dispersed echelle spectra
Authors: Piskunov, N. E.; Valenti, J. A.
2002A&A...385.1095P Altcode:
We describe advanced image processing algorithms, implemented in a
data analysis package for conventional and cross-dispersed echelle
spectra. Comparisons with results from other packages illustrate
the outstanding quality of the new REDUCE package, particularly
in terms of resulting noise level and treatment of CCD defects and
cosmic ray spikes. REDUCE can be adapted relatively easily to handle
a variety of instrument types, including spectrographs with prism or
grating cross-dispersers, possibly fed by a fiber or image slicer,
etc. In addition to reduced spectra, an accurate spatial profile is
recovered, providing valuable information about the spectrograph PSF
and simplifying scattered light corrections. Based on data obtained
with the VLT UVES and SAAO Giraffe spectrometers.

---------------------------------------------------------
Title: Detailed analysis of Balmer lines in cool dwarf stars
Authors: Barklem, P. S.; Stempels, H. C.; Allende Prieto, C.;
Kochukhov, O. P.; Piskunov, N.; O'Mara, B. J.
2002A&A...385..951B Altcode: 2002astro.ph..1537B
An analysis of Hα and Hβ spectra in a sample of 30 cool dwarf and
subgiant stars is presented using MARCS model atmospheres based on the
most recent calculations of the line opacities. A detailed quantitative
comparison of the solar flux spectra with model spectra shows that
Balmer line profile shapes, and therefore the temperature structure
in the line formation region, are best represented under the mixing
length theory by any combination of a low mixing-length parameter alpha
and a low convective structure parameter y. A slightly lower effective
temperature is obtained for the sun than the accepted value, which we
attribute to errors in models and line opacities. The programme stars
span temperatures from 4800 to 7100 K and include a small number of
population II stars. Effective temperatures have been derived using
a quantitative fitting method with a detailed error analysis. Our
temperatures find good agreement with those from the Infrared Flux
Method (IRFM) near solar metallicity but show differences at low
metallicity where the two available IRFM determinations themselves are
in disagreement. Comparison with recent temperature determinations
using Balmer lines by Fuhrmann (\cite{fuhrmann98, fuhrmann00}),
who employed a different description of the wing absorption due
to self-broadening, does not show the large differences predicted
by Barklem et al. (\cite{bpo:hyd}). In fact, perhaps fortuitously,
reasonable agreement is found near solar metallicity, while we find
significantly cooler temperatures for low metallicity stars of around
solar temperature. Based on observations collected at the Isaac Newton
Telescope, La Palma, Spain, and McDonald Observatory, Texas, USA.

---------------------------------------------------------
Title: Abundance stratification and pulsation in the atmosphere of
the roAp star boldmath gamma Equulei
Authors: Ryabchikova, T.; Piskunov, N.; Kochukhov, O.; Tsymbal, V.;
Mittermayer, P.; Weiss, W. W.
2002A&A...384..545R Altcode:
We present the evidence for abundance stratification in the atmosphere
of the rapidly oscillating Ap star gamma Equ. Ca, Cr, Fe, Ba, Si,
Na seem to be overabundant in deeper atmospheric layers, but normal
to underabundant in the upper layers with a transition in the typical
line forming region of -1.5&lt;log tau 5000&lt;-0.5. This
stratification profile agrees well with diffusion theory for Ca
and Cr, developed for cool magnetic stars with a weak mass loss of
{~}2.5*E-15 Msun yr-1. Pr and Nd from
the rare earth elements have an opposite profile. Their abundance is
more than 6 dex higher above log tau 5000 ~ -8.0 than in
the deeper atmospheric layers. We further discuss the implications of
abundance stratification in the context of radial velocity amplitudes
and phases observed by Kochukhov &amp; Ryabchikova (2001) for a
variety of spectral lines and elements using high spectral and time
resolved, high S/N observations. Based on observations obtained at
the European Southern Observatory (La Silla, Chile), and the South
African Astronomical Observatory.

---------------------------------------------------------
Title: Spectroscopy of Rapidly Oscillating Ap Stars
Authors: Weiss, W. W.; Ryabchikova, T. A.; Savanov, I.; Piskunov, N.;
Tsymbal, V.; Mittermayer, P.; Martinez, P.; Kochukhov, O.; Nesvacil, N.
2002ASPC..259..280W Altcode: 2002IAUCo.185..280W; 2002rnpp.conf..280W
No abstract at ADS

---------------------------------------------------------
Title: Doppler Imaging of stellar magnetic fields. I. Techniques
Authors: Piskunov, N.; Kochukhov, O.
2002A&A...381..736P Altcode:
We describe our latest Magnetic Doppler Imaging (MDI) code capable of
simultaneously reconstructing the magnetic field vector and chemical
composition distribution over the stellar surface. Input data consists
of polarization measurements in the line profiles and the reconstruction
is performed by solving the regularized inverse problem. The code
incorporates the latest developments in the radiative transfer, the
optimization and parallel computing techniques. We have also developed
a new regularization method that allows application of our MDI code to
incomplete data sets (e.g. only intensity and circular polarization) by
restricting possible configurations of the field. Numerical experiments
to be presented in a forthcoming paper demonstrate what can be achieved
with MDI and allow studying of systematic errors that can cause serious
distortions of the maps.

---------------------------------------------------------
Title: VizieR Online Data Catalog: LTE spectrum synthesis in magnetic
atmospheres (Wade+, 2001)
Authors: Wade, G. A.; Bagnulo, S.; Kochukhov, O.; Landstreet, J. D.;
Piskunov, N.; Stift, M. J.
2001yCat..33740265W Altcode:
Files table4.dat contain calculated Stokes IQUV local line profiles of
Fe II 4923.9 shown in Fig. 4 of this paper. Profile sets are provided
for 0.1, 5 and 20kG magnetic fields, with vector orientation ψ=40°,
φ=0°, disc centre and epsfe=4.6. (3 data files).

---------------------------------------------------------
Title: LTE spectrum synthesis in magnetic stellar atmospheres. The
interagreement of three independent polarised radiative transfer codes
Authors: Wade, G. A.; Bagnulo, S.; Kochukhov, O.; Landstreet, J. D.;
Piskunov, N.; Stift, M. J.
2001A&A...374..265W Altcode:
With the aim of establishing a benchmark for the detailed
calculation of the polarised line profiles of magnetic stars, we
describe an intercomparison of LTE Stokes profiles calculated using
three independent, state-of-the-art magnetic spectrum synthesis
codes: Cossam, Invers10 and Zeeman2. We find, upon establishing a
homogeneous basis for the calculations (identical definitions of the
Stokes parameters and the magnetic and stellar reference frames,
identical input model stellar atmosphere, identical input atomic
data, and identical chemical element abundances and magnetic field
distributions), that local and disc-integrated Stokes IQUV profiles
of Fe II lambda 4923.9 calculated using the three codes agree
very well. For the illustrative case of disc-integrated profiles
calculated for abundance log nFe/ntot=-4.60,
dipole magnetic field intensity Bd=5 kG, and projected
rotational velocity v_esin i=20 km s-1, Stokes I profiles
(depth ~ 40% of the continuum flux Ic) agree to within about
0.05% rms of Ic, Stokes V profiles (full amplitude ~ 10%)
to within about 0.02% rms of Ic, and Stokes Q and U profiles
(full amplitudes ~ 2%) at the sub-0.01% rms level. These differences
are sufficiently small so as to allow for congruent interpretation of
the best spectropolarimetric data available, as well as for any data
likely to become available during the near future. This indicates that
uncertainties in modeling Stokes profiles result overwhelmingly from
uncertainties in input atomic and physical data, especially the state
and structure of model stellar atmospheres.

---------------------------------------------------------
Title: Formation of Fe X-Fe XIV coronal lines in the accretion shock
of T Tauri stars
Authors: Lamzin, S. A.; Stempels, H. C.; Piskunov, N. E.
2001A&A...369..965L Altcode:
Specific intensities of the strongest Fe x-Fe xiV\ coronal lines were
calculated in the framework of our accretion shock model (Lamzin
\cite{Lamzin1998}). These lines are formed in a region immediately
behind the front of the accretion shock, therefore, the gas velocity in
the line formation region is close to 1/4 of the infall velocity. It
appears that iron coronal lines in the optical band (e.g. [Fe x]
6376 Å and [Fe xiV] 5304 Å) are too weak to be observed in spectra
of T Tauri stars, but the UV lines (e.g. [Fe xi] 1467 Å and [Fe xiI]
1349 Å) can possibly be detected. In agreement with our calculations
we could not detect the [Fe x] 6376 Å and [Fe xiV] 5304 Å lines in
low noise UVES spectra of RU Lup where the accretion luminosity is
ten times larger than the bolometric luminosity of the underlying
star. At the same time we detected the [Fe xi] 1467 Å line in a
HST/GHRS spectrum of RY Tau which suggests that the accretion rate of
the star in its quiescent state is ~2 10-9 M_sun/yr. As
a byproduct of the study we found that for RY Tau the interstellar
extinction coefficient A_V is closer to 0.5{m} than to
1.0{m}. For DF Tau, the observed upper limit for the flux
of the [Fe xiI] 1349 Å line in HST/GHRS spectra is in agreement with
an accretion rate of 2 10-9 M_sun/yr as found by Lamzin
et al. (\cite{Lamzin2000}). As a critical test of our calculations we
predict that the [Fe xi] 1467 Å line in the spectrum of RU Lupi should
be relatively strong: we expect the flux to be near 10-15
erg/s/cm2.

---------------------------------------------------------
Title: The core-wing anomaly of cool Ap stars. Abnormal Balmer
Profiles
Authors: Cowley, C. R.; Hubrig, S.; Ryabchikova, T. A.; Mathys, G.;
Piskunov, N.; Mittermayer, P.
2001A&A...367..939C Altcode: 2000astro.ph.12102C
The profiles of Hα in a number of cool Ap stars are anomalous. Broad
wings, indicative of temperatures in the range 7000-8000 K end abruptly
in narrow cores. The widths of these cores are compatible with those
of dwarfs with temperatures of 6000 K or lower. This profile has been
known for Przybylski's star, but it is seen in other cool Ap stars. The
Hβ profile in several of these stars shows a similar core-wing anomaly
(CWA). In Przybylski's star, the CWA is probably present at higher
Balmer members. We are unable to account for these profiles within
the context of LTE and normal dwarf atmospheres. We conclude that
the atmospheres of these stars are not “normal”. This is contrary
to a notion that has long been held. Based on observations obtained
at the European Southern Observatory, Paranal, Chile (ESO programme
No. 65.I-0644) and the South African Astronomical Observatory (SAAO).}

---------------------------------------------------------
Title: Model Atmospheres with Individualized Abundances
Authors: Piskunov, N.; Kupka, F.
2001ApJ...547.1040P Altcode:
We describe a new method for computing opacity distribution functions
(ODFs) for model atmosphere calculations. The method is tailored to
model the atmospheres of individual stars on a modern workstation. Our
goal is the computation of model atmospheres for stars with abundances
significantly different from the solar or scaled solar composition
typically used for grid calculations. As a consistency test, we show
that the new procedure is able to reproduce the ODFs and existing model
atmospheres for solar abundances, and we describe models for stars
with peculiar abundances. We demonstrate that while mild chemical
peculiarities can be well represented by scaled solar models, the
extreme cases result in a very different atmospheric structure with no
analogs in scaled solar grids. Such a structure influences the emerging
spectrum as is clearly seen both in the observed flux distribution and
in the line ratios that are much better represented by the new models.

---------------------------------------------------------
Title: Magnetic Doppler Imaging of α CVn
Authors: Kochukhov, O.; Piskunov, N.; Ilyin, I.; Ilyina, S.;
Tuominen, I.
2001ASPC..248..321K Altcode: 2001mfah.conf..321K
No abstract at ADS

---------------------------------------------------------
Title: Chemical Stratification in Magnetic Ap Stars
Authors: Wade, G. A.; Ryabchikova, T. A.; Bagnulo, S.; Piskunov, N.
2001ASPC..248..373W Altcode: 2001mfah.conf..373W
No abstract at ADS

---------------------------------------------------------
Title: Magnetic Doppler Imaging of CP Stars
Authors: Piskunov, N.
2001ASPC..248..293P Altcode: 2001mfah.conf..293P
No abstract at ADS

---------------------------------------------------------
Title: The Search and Modeling of Magnetic Fields on M dwarfs
(CD-ROM Directory: contribs/kochuk)
Authors: Kochukhov, O. P.; Piskunov, N. E.; Valenti, J. A.;
Johns-Krull, C. M.
2001ASPC..223..985K Altcode: 2001csss...11..985K
No abstract at ADS

---------------------------------------------------------
Title: Using FeH to Measure Magnetic Fields on Cool Stars and Brown
Dwarfs (CD-ROM Directory: contribs/valenti)
Authors: Valenti, J. A.; Johns-Krull, C. M.; Piskunov, N. E.
2001ASPC..223.1579V Altcode: 2001csss...11.1579V
No abstract at ADS

---------------------------------------------------------
Title: Recent Developments of the VALD Database (CD-ROM Directory:
contribs/stempels)
Authors: Stempels, H. C.; Piskunov, N.; Barklem, P. S.
2001ASPC..223..878S Altcode: 2001csss...11..878S
No abstract at ADS

---------------------------------------------------------
Title: Doppler Imaging of Eclipsing Binary Systems ER Vul and TY Pyx
(CD-ROM Directory: contribs/piskunov)
Authors: Piskunov, N.; Vincent, A.; Duemmler, R.; Ilyin, I.;
Tuominen, I.
2001ASPC..223.1285P Altcode: 2001csss...11.1285P
No abstract at ADS

---------------------------------------------------------
Title: Magnetic Doppler Imaging of Chemically Peculiar Stars
Authors: Piskunov, N.; Kochukhov, O.
2001LNP...573..238P Altcode: 2001astr.conf..238P
We present the results of numerical experiments and real applications
of our new Magnetic Doppler Imaging code INVERS10. The code is capable
of simultaneously reconstructing the surface distribution of magnetic
field vectors and one chemical element from a time sequence of line
profiles measured in four Stokes parameters. The application of the
code to a well studied magnetic Ap star 2 °CVn recovered a field
distribution, resembling an oblique dipole with the strength and
orientation consistent with those derived with other techniques.

---------------------------------------------------------
Title: Time-Resolved Spectroscopy of the roAp Star γ Equ
Authors: Kochukhov, O.; Ryabchikova, T.; Piskunov, N.
2001ASPC..248..341K Altcode: 2001mfah.conf..341K
No abstract at ADS

---------------------------------------------------------
Title: Hydrogen Line Formation in Cool Stars (CD-ROM Directory:
contribs/barklem1)
Authors: Barklem, P. S.; Kochukhov, O.; Piskunov, N.; O'Mara, B. J.;
Stempels, H. C.
2001ASPC..223..766B Altcode: 2001csss...11..766B
No abstract at ADS

---------------------------------------------------------
Title: New Measurements of T Tauri Magnetic Fields: Testing
Magnetospheric Accretion
Authors: Johns-Krull, C. M.; Valenti, J. A.; Piskunov, N. E.; Saar,
S. H.; Hatzes, A. P.
2001ASPC..248..527J Altcode: 2001mfah.conf..527J
No abstract at ADS

---------------------------------------------------------
Title: The Search and Modelling of Magnetic Fields on M Dwarfs
Authors: Kochukhov, O.; Piskunov, N.; Valenti, J.; Johns-Krull, C.
2001ASPC..248..219K Altcode: 2001mfah.conf..219K
No abstract at ADS

---------------------------------------------------------
Title: Self-broadening in Balmer line wing formation in stellar
atmospheres
Authors: Barklem, P. S.; Piskunov, N.; O'Mara, B. J.
2000A&A...363.1091B Altcode: 2000astro.ph.10022B
Details of a theory of self-broadening of hydrogen lines are
presented. The main features of the new theory are that the
dispersive-inductive components of the interaction (van der Waals
forces) have been included, and the resonance components have been
computed by perturbation theory without the use of the multipole
expansion. The theory is applied to lower Balmer lines and the
theoretical and observational impact of the new broadening theory
is examined. It is shown that this theory leads to considerable
differences in the predicted line profiles in cool stars when compared
with previous theories which include only resonance interactions. In
particular, the effect is found to be very important in metal poor
stars. The theory provides a natural explanation for the behaviour
of effective temperatures derived from Balmer lines by others using
a theory which includes only resonance broadening. When applied to
Balmer lines in the solar spectrum the theory predicts an improved
agreement between observed and computed profiles for models which
also match limb darkening curves and rules out a model which does
not. However significant discrepancies still remain which could be
due to inadequacies in our theory or the atmospheric model or both.

---------------------------------------------------------
Title: Abundance analysis of roAp stars. V. HD 166473
Authors: Gelbmann, M.; Ryabchikova, T.; Weiss, W. W.; Piskunov, N.;
Kupka, F.; Mathys, G.
2000A&A...356..200G Altcode:
This fifth paper in a sequence on abundance analyses of roAp stars
features several improvements and complements over the previous
investigations: i. The new VALD-2 atomic data base was used which
significantly improves the analysis of C, N, O, and rare earth
elements (REE) and in particular includes also some doubly ionized
REE species. ii. An individual opacity distribution function table
was generated for a successful synthesis of photometric indices of
this very peculiar star. iii. The influence of a (rather strong)
magnetic field on abundance determinations is studied and presented
for 30 elements. iv. Our investigation of 33 elements (45 ions) is
the hitherto most complete chemical analysis of a chemically peculiar
star, using modern tools. Similar to the four roAp stars analysed
by us so far (alpha Cir: Kupka et al. 1996, HD 203932: Gelbmann
et al. 1997, gamma Equ: Ryabchikova et al. 1997a, and HD 24712:
Ryabchikova et al. 1997b) we find nearly solar abundances of Fe and
Ni, and a definite overabundance of Cr and especially Co. Rare earth
elements have large overabundances, whereas C and O are underabundant
relative to the Sun. This pattern seems to be a common property of the
chemically peculiar (CP2, Ap) stars. A new and most striking result
is the discovery of the anomalous line strengths of the second ions
of REE resulting in an abundance increase of up to +1.5 dex, compared
to values obtained from lines of the first ions. This anomaly is not
found in non-roAp and “normal” stars. Based on observations obtained
at the European Southern Observatory (La Silla, Chile)

---------------------------------------------------------
Title: A list of data for the broadening of metallic lines by neutral
hydrogen collisions
Authors: Barklem, P. S.; Piskunov, N.; O'Mara, B. J.
2000A&AS..142..467B Altcode:
A list of data for the broadening by neutral hydrogen collisions of many
astrophysically important spectral lines, which has been incorporated
into the Vienna Atomic Line Database (VALD), is presented. Data for
lines of neutral atoms are interpolated from the tabulated data of
Anstee &amp; O'Mara (\cite{ao:sp}), Barklem &amp; O'Mara (\cite{bo:pd}),
and Barklem et al. (\cite{bor:df}). Data for lines of singly ionised
atoms are compiled from the calculations by Barklem &amp; O'Mara
(\cite{bo:ion1,bo:ion2}). The list at present contains data for
4891 lines between 2300 and 13000 Ä of elements from Li to Ni. We
examine the statistical impact of the new theory by comparison with
the previously available data. We also demonstrate the direct effect on
spectral synthesis calculations. Table~1 is only available in electronic
form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via anonymous ftp to ftp.astro.uu.se/pub/Spectra/barklem/hlist/

---------------------------------------------------------
Title: VizieR Online Data Catalog: Broadening of metallic lines by
H collisions (Barklem+ 2000)
Authors: Barklem, P. S.; Piskunov, N.; O'Mara, B. J.
2000yCat..41420467B Altcode:
File table1 is a list of theoretical data for the broadening of metallic
lines by collisions with neutral hydrogen atoms. The list contains data
for 4891 spectral lines between 2300 and 13000 Angstroms of elements
from Li to Ni. (1 data file).

---------------------------------------------------------
Title: Self broadening of hydrogen lines: initial results
Authors: Barklem, P. S.; Piskunov, N.; O'Mara, B. J.
2000A&A...355L...5B Altcode:
For the first time broadening by both resonance and dispersive-inductive
interactions with H-atoms are included in the formation of Balmer lines
in cool stars, without the use of a multipole expansion. Comparison of
synthetic profiles with observed profiles for the Sun and two late F
dwarfs shows that this improvement in broadening theory accounts for
some of the problems found in previous work. It is anticipated that
planned future developments in the theory of self broadening will lead
to further improve ments in the modelling of cool star atmospheres.

---------------------------------------------------------
Title: VALD-2 -- The New Vienna Atomic Line Database
Authors: Kupka, F. G.; Ryabchikova, T. A.; Piskunov, N. E.; Stempels,
H. C.; Weiss, W. W.
2000BaltA...9..590K Altcode: 2000OAst....9..590K
We provide a brief outline of the concepts and facilities of the Vienna
Atomic Line DataBase in its new version 2. A summary of contents and
recommendations how to use the VALD-2 are given. We conclude by a few
applications planned for future releases of VALD.

---------------------------------------------------------
Title: Spectral and polarimetric observations of the star HD 37022
(θ1 Ori C)
Authors: Kudryavtsev, D. O.; Piskunov, N. E.; Romanyuk, I. I.;
Chountonov, G. A.; Shtol', V. G.
2000mfcp.proc...64K Altcode:
HD 37022 (θ1 Ori C) is a young star of spectral type O7
V, the brightest star in the Trapezium of the Orion Nebulae (M42). It
has a synchronous spectral variability in the optical, ultraviolet and
X--rays regions with a period P=15.422d. For the explanation
of this variability many authors suggest a magnetic rotator modulating
the stellar wind. During 1996-97 we made a series of observations
of θ1 Ori C at the 6 m telescope of SAO RAS, using the
circular polarization analyzer and hydrogen--line magnetometer, to
make sure that a magnetic field exists in this star. In this paper we
publish the results of measurements of the effective magnetic field
and Stokes parameters. The value of the effective magnetic field is
within the measurement errors and apparently not more than 500G.

---------------------------------------------------------
Title: The new magnetic Doppler imaging code
Authors: Piskunov, N.
2000mfcp.proc...96P Altcode:
In this paper we describe a new Magnetic Doppler Imaging (MDI) code
INVERS10 designed to reconstruct magnetic fields on the surfaces
of CP stars. The code is based on a state-of-the-art radiative
transfer solver and efficient minimization technique. It is aimed at
multi-processor calculations. This new tool is capable of reconstructing
the distribution of magnetic field vectors and abundance of one chemical
element from a time sequence of four Stokes parameters, observed with
sufficient time and spectral resolution. No assumptions about field
geometry (e.g. multipolar, radial etc.) are necessary. In addition,
INVERS10 is capable of simulating the observed profiles for a given
field geometry and abundance distribution. We also show some results of
numerical experiments and discuss future applications of the new code.

---------------------------------------------------------
Title: The Three-dimensional Structure of the Warm Local Interstellar
Medium. I. Methodology
Authors: Linsky, Jeffrey L.; Redfield, Seth; Wood, Brian E.; Piskunov,
Nikolai
2000ApJ...528..756L Altcode:
In this first in a series of papers, we develop a methodology for
constructing three-dimensional models of the local interstellar
cloud (LIC) and adjacent warm clouds in the local interstellar medium
(LISM). Our models are based on the column density of neutral hydrogen
gas (NHI) inferred primarily from measurements of the
deuterium column density toward nearby stars obtained from the analysis
of Hubble Space Telescope ultraviolet spectra. We also use values of
NHI inferred from spectra of hot white dwarfs and B-type
stars obtained by the Extreme Ultraviolet Explorer satellite. These
very different methods give consistent results for the three white
dwarf stars in common. We assume that along each line of sight all
interstellar gas moving with a speed consistent with the LIC velocity
vector has a constant density, NHI=0.10 cm-3,
and extends from the heliosphere to an edge determined by the value of
NHI moving at this speed. A number of stars have velocities
and/or depletions that indicate absorption by other warm clouds in
their lines of sight. On this basis α Cen A and B and probably also
ɛ Ind lie inside the Galactic center (G) cloud, HZ 43 and 31 Com
lie inside what we call the north Galactic pole cloud, and β Cet is
located inside what we call the south Galactic pole cloud. We show the
locations of these clouds in Galactic coordinates. The Sun is located
very close to the edge of the LIC toward the Galactic center and the
north Galactic pole. The absence of Mg II absorption at the LIC velocity
toward α Cen indicates that the distance to the edge of the LIC in
this direction is &lt;=0.05 pc and the Sun should leave the LIC and
perhaps enter the G cloud in less than 3000 yr. Comparison of LIC and
total values of NHI toward pairs of stars with separations
between 0.9d and 20° reveals a pattern of good agreement so long as
both stars lie within 60 pc of the Sun. Thus the LIC and perhaps also
other nearby warm clouds have shapes that are smooth on these angular
scales. In our second paper we will therefore fit the shape of the
LIC with a set of smooth basis functions (spherical harmonics). Based on observations with the NASA/ESA Hubble Space Telescope,
obtained at the Space Telescope Science Institute, which is operated
by the Association of Universities for Research in Astronomy, Inc.,
under NASA contract NAS5-26555.

---------------------------------------------------------
Title: The news about Vienna Atomic Line Data Base
Authors: Piskunov, N.; Ryabchikova, T. A.; Weiss, W. W.
2000mfcp.proc..194P Altcode:
We describe the main changes in the “Vienna Atomic Line Data Base”
(VALD, Piskunov et al., 1995 and Piskunov, 1996) that have been
made since the first release in 1994. The original VALD lists have
been complemented with critically evaluated data obtained from
experimental measurements and theoretical calculations which are
necessary for computing state-of-the-art line opacities in stellar
atmospheres, as well as for spectral synthesis for high precision
studies (e.g. abundances, radial velocities etc.). In this paper we
present new and improved data sets for chemical elements that have
already been included in VALD, for new elements and for additional
higher ionized species. Software modifications allow remote users of
VALD to specify individual extraction parameters as an alternative to
the default settings of the VALD team and to have direct control over
the quality ranking of line data. The new World--Wide--Web interface
provides easy access to all new features. The support for the mirror
site permitted opening of two additional VALD servers at Hoddard
Space Flight Center (USA) and at Uppsala Astronomical Observatory
(Sweden). For proper crediting of all authors of atomic data, VALD
now includes a compilation of all publications used to any replies.

---------------------------------------------------------
Title: Multi element Doppler imaging of AP stars. I. He, Mg, Si,
CR and Fe surface distribution for CU Virginis
Authors: Kuschnig, R.; Ryabchikova, T. A.; Piskunov, N. E.; Weiss,
W. W.; Gelbmann, M. J.
1999A&A...348..924K Altcode:
We present the distribution of helium, magnesium, silicon, chromium
and iron on the surface of the fast rotating magnetic B9p Si star CU
Virginis, obtained with a Doppler Imaging inversion code. A clearly
defined helium spot coincides with the position of one magnetic
pole whereas silicon, chromium and iron accumulate in regions where
the magnetic field lines are dominantly horizontal in the stellar
atmosphere. The distribution of magnesium is significantly different
compared to the other elements. The Hdelta line varies in phase with the
helium spot and the magnetic pole and the line profiles can be fitted
within the observational errors with model atmospheres of constant
{T_eff } of 12500 K, but different surface gravity. We compare our
observations with current concepts for diffusion in magnetic chemically
peculiar stars and find good agreement. Based on observation obtained
at the Observatoire d'Haute-Provence.

---------------------------------------------------------
Title: VALD-2: Progress of the Vienna Atomic Line Data Base
Authors: Kupka, F.; Piskunov, N.; Ryabchikova, T. A.; Stempels, H. C.;
Weiss, W. W.
1999A&AS..138..119K Altcode:
We describe the updated version of the Vienna Atomic Line Data
Base (VALD, \cite[Piskunov et al. 1995)]{pis95} which represents a
considerable improvement over the first installation from 1994. The
original line lists have been complemented with critically evaluated
data obtained from experimental measurements and theoretical
calculations which are necessary for computing state-of-the-art line
opacities in stellar atmospheres, as well as for synthesizing spectra
for high precision analyses. In this paper, we present new and improved
data sets for neutral species and ions of Si, P, Sc, Ti, V, Cr, Mn, Fe,
Co, Ni, Cu, Zn, Y, Zr, Ru, Xe, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er,
Tm, Yb, Lu, Re, Pt, Au, Hg, and Pb. For some species data are available
in VALD for the first time. We explain our choice of quality rankings by
reviewing the literature for the new data and by comparison with source
lists included into VALD. For some cases, we produced new line data
by weighted averaging of data from different sources with individual
error estimates in order to increase the reliability of VALD line
lists. Software modifications allow remote users of VALD to specify
individual extraction parameters as an alternative to the default
settings of the VALD team and to have direct control over the quality
ranking of line data. A World-Wide-Web interface is described which
provides easy access to all new features. To simplify proper crediting
of all authors of atomic data, VALD now includes a compilation of all
publications used in each type of reply. Finally, we briefly discuss
the future roadmap of VALD developments, including the incorporation
of molecular transitions and integration with external data
bases. http://www.astro.univie.ac.at/~vald http://www.astro.uu.se/~vald

---------------------------------------------------------
Title: Eu III identification and Eu abundance in CP stars
Authors: Ryabchikova, T.; Piskunov, N.; Savanov, I.; Kupka, F.;
Malanushenko, V.
1999A&A...343..229R Altcode:
We report the first identification of the Eu iii lambda 6666.347 line
in optical spectra of CP stars. This line is clearly present in the
spectra of HR 4816, 73 Dra, HR 7575, beta CrB, and alpha (2) CVn,
while it is marginally present or absent in spectra of the roAp stars
(rapidly oscillating Ap stars, cf. Kurtz 1990) alpha Cir, gamma Equ,
HD 203932, GZ Lib (33 Lib), and HD 24712. Careful synthetic spectrum
calculations for the Eu ii lambda 6645.11 line taking into account
hyperfine, isotopic, and magnetic splittings allow us to obtain more
accurate Eu abundances in the atmospheres of 9 CP stars. In most
cases the derived abundances are significantly lower than the previous
results reported for some of the stars based on coarse analysis of the
famous blue Eu ii lines. Assuming an ionization balance in the stellar
atmospheres we give an estimate of the astrophysical oscillator strength
log (gf)=1.18 +/- 0.14 for the Eu iii lambda 6666.347 line. This value
is obtained without taking into account a possible hyperfine-splitting
which is unknown for this Eu iii line. We also provide astrophysical
gf-values for Eu iii lambda lambda 7221.838, 7225.151, and 8079.071.

---------------------------------------------------------
Title: Study of Delta and Roper resonances excitation in light nuclei
induced reactions
Authors: Strokovsky, E. A.; Azhgirey, L. S.; Malinina, L. V.; Piskunov,
N. M.; Sitnik, I. M.; Boivin, M.; Hennino, T.; Kunne, R.; Kagarlis,
M.; Radvanyi, P.; Tomasi-Gustaffson, E.; Boyard, J. -L.; Farhi,
L.; Jourdain, J. C.; Ramstein, B.; Roy-Stephan, M.; Alkhazov, G. D.;
Kravtsov, A. V.; Mylnikov, V. A.; Orichtchin, E. M.; Prokofiev, A. N.;
Razmyslovich, B. V.; Tkach, I. I.; Volkov, S. S.; Zhdanov, A. A.;
Dahl, R.; Drews, M.; Ellegaard, F. C.; Gaarde, C.; Larsen, J. S.;
Skousen, M.; Morsch, P.; Augustiniak, W.; Zupranski, P.; Perdrisat,
C. F.; Punjabi, V.
1999fbpp.conf..495S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Observing Hot Stars in all Four Stokes Parameters
Authors: Eversberg, Thomas; Moffat, Anthony F. J.; Debruyne, Michael;
Rice, John B.; Piskunov, Nikolai; Bastien, Pierre; Wehlau, William H.;
Chesneau, Olivier
1999LNP...523..107E Altcode: 1999IAUCo.169..107E; 1999vnss.conf..107E
We introduce a new polarimeter unit which, mounted at the Cassegrain
focus of any telescope and fiber-connected to a fixed CCD spectrograph,
as able to measure all Stokes parameters I, Q, U and V photon-noise
limited across spectral lines of bright stellar targets and other
point sources in a quasi-simultaneous manner. We briefly outline the
technical design of the polarimeter unit and the linear algebraic
Mueller calculus for obtaining polarization parameters of any point
source. In addition, practical limitations of the optical elements are
discussed. We present first results obtained with our spectropolarimeter
for three prototype hot-star.

---------------------------------------------------------
Title: Stellar activity and magnetism
Authors: Piskunov, N.
1999anot.conf..204P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Modeling magnetic fields on stars other than the Sun
Authors: Piskunov, N.
1999ASSL..243..515P Altcode: 1999sopo.conf..515P
No abstract at ADS

---------------------------------------------------------
Title: The William-Wehlau Spectropolarimeter: Observing Hot Stars
in All Four Stokes Parameters
Authors: Eversberg, Thomas; Moffat, Anthony F. J.; Debruyne, Michael;
Rice, John B.; Piskunov, Nikolai; Bastien, Pierre; Wehlau, William H.;
Chesneau, Olivier
1998PASP..110.1356E Altcode:
We introduce a new polarimeter unit, which, mounted at the Cassegrain
focus of any telescope and fiber-connected to a fixed CCD spectrograph,
is able to measure all Stokes parameters I, Q, U, and V across
spectral lines of bright stellar targets and other point sources in a
quasi-simultaneous manner. Applying standard reduction techniques for
linearly and circularly polarized light, we are able to obtain photon
noise-limited line polarization. We briefly outline the technical design
of the polarimeter unit and the linear algebraic Mueller calculus for
obtaining polarization parameters of any point source. In addition,
practical limitations of the optical elements are outlined. We present
first results obtained with our spectropolarimeter for four bright,
hot-star targets. We confirm previous results for Hα in the bright
Be star gamma Cas and find linear depolarization features across the
emission-line complex C III/C IV (5696/5808 Å) of the WR + O binary
gamma^2 Vel. We also find circular line polarization in the strongly
magnetic Ap star 53 Cam across its Hα absorption line. No obvious
line polarization features are seen across Hα in the variable O star
theta^1 Ori C above the sigma~0.2% instrumental level.

---------------------------------------------------------
Title: Spectral Synthesis of TiO Lines
Authors: Valenti, Jeff A.; Piskunov, Nikolai; Johns-Krull,
Christopher M.
1998ApJ...498..851V Altcode:
We explore the extent to which current titanium oxide (TiO) line
data and M dwarf model atmospheres can be used to reproduce an R =
120,000 optical spectrum of the relatively inactive star Gliese 725B
(M3.5 V). We find that tabulated TiO wavelengths have errors large
enough to complicate line identification, especially for transitions
involving higher vibrational states. We determine empirical
wavelength corrections for 12 strong γ-bands near 6680 and 7090
Å. For the sequence of orbital quantum numbers, J, within any one
of these bands, our observations confirm the predicted line spacing,
thereby validating the rotational constants for low vibrational
levels. However, the predicted wavelengths have zero-point errors
that differ for each overlapping band. Next, we compare observed
and synthetic spectra near 8463 Å, where an ɛ Q3 0-0
band head is expected, demonstrating that the electronic oscillator
strength of 0.014 advocated by Jørgensen is too large by at least a
factor of 5. This has a minor effect on the structure of theoretical
model atmospheres. Using our empirically corrected TiO wavelengths,
we compute a grid of synthetic spectra for Allard &amp; Hauschildt
models spanning a range in effective temperature (Teff),
surface gravity (log g), and metallicity ([M/H]). Interpolating in
this grid of synthetic spectra, we simultaneously fit observations of
the TiO band head region near 7088 Å and five Ti I and Fe I lines
near 8683 Å. For Gl 725B, we find Teff = 3170 +/- 71 K,
log g = 4.77 +/- 0.14, [M/H] = -0.92 +/- 0.07, and vmac =
1.1 +/- 0.7 km s-1. We show that by using both atomic and
molecular lines as constraints, systematic uncertainties in derived
stellar parameters can be reduced. These parameters are consistent with
published values obtained by other means, but more stringent tests would
be useful. In the Appendix, we tabulate wavelengths, identifications,
relative line strengths, and other properties of the strongest band
heads in the α, β, γ, γ', δ, ɛ, and φ electronic systems of TiO.

---------------------------------------------------------
Title: Astronephography: the 3-D shape of the Local Interstellar Cloud
Authors: Linsky, J. L.; Piskunov, N.; Wood, B. E.
1998AAS...192.1018L Altcode: 1998BAAS...30..830L
GHRS spectra of 19 mostly late-type stars provide interstellar hydrogen
and metal column densities along these lines of sight with sufficient
resolution to resolve individual clouds. For 16 of these lines of sight
we can infer the hydrogen column density at the projected velocity
of the Local Interstellar Cloud (LIC). We construct a 3 dimensional
representation of the LIC by assuming that the neutral hydrogen density
in the cloud is the same as the highest mean density observed, about
0.1 cm(-3) , and that the LIC extends continuously along each line of
sight to a distance determined by the hydrogen column density and the
assumed density. We will present our model of the LIC as an animated
video that shows its shape from different directions. We find that
the hydrogen column densities obtained from EUVE spectra of white
dwarfs are in excellent agreement with the GHRS column densities for
the stars. Also, some other nearby white dwarfs fit our LIC model
well and are included in the model. As viewed from the North Galactic
Pole, the LIC has an irregular shape with the Sun very near the edge
toward the Galactic Center and very little column density in the first
and fourth Galactic quadrants. As viewed from in the Galactic plane,
there is more material to the south and the cloud has narrow extensions
toward the Galactic Center and toward Galactic longitude 270 Degrees. We
propose that the study of the structure of interstellar clouds be called
"astronephography" based on the Greek word for cloud, "nephos". This
work is supported by NASA grants to the University of Colorado.

---------------------------------------------------------
Title: CP star atmospheres based on individual ODFs
Authors: Kupka, F.; Piskunov, N. E.
1998CoSka..27..228K Altcode: 1998astro.ph..5057K
We describe a new method for the computation of opacity distribution
functions (ODFs) useful to calculate one-dimensional model atmospheres
in local thermal equilibrium (LTE). The new method is fast enough to
be applied on current workstations and allows the computation of model
atmospheres which deviate significantly from (scaled) solar chemical
composition. It has reproduced existing ODFs and model atmospheres
for solar abundances. Depending on the type of chemical peculiarity
the "individual" model atmosphere may have a structure and surface
fluxes similar to atmospheres based on (scaled) solar abundances or
deviate in a way that cannot be reproduced by any of the conventional
models. Examples are given to illustrate this behavior. The availability
of models with "individualized" abundances is crucial for abundance
analyses and Doppler imaging of extreme CP stars.

---------------------------------------------------------
Title: IOTA Cas: Multi-element Doppler imaging and magnetic field
geometry
Authors: Kuschnig, R.; Wade, G. A.; Hill, G. M.; Piskunov, N.
1998CoSka..27..470K Altcode: 1998astro.ph..5243K
In order to clarify the role of the magnetic field in generating
abundance inhomogeneities in the atmospheres of Ap stars, we present
new abundance Doppler images and an approximate magnetic field geometry
for the Ap star iota Cas.

---------------------------------------------------------
Title: Radiative transfer in Doppler Imaging
Authors: Piskunov, N.
1998CoSka..27..374P Altcode: 1998astro.ph..5048P
The modern Doppler Imaging (DI) technique allows the reconstruction
of different stellar surface structures based on accurate calculation
of spectra of specific intensity. New applications like the mapping
of the magnetic field vector put very stringent requirements on the
radiative transfer (RT) solver which should be accurate, fast, and
robust against numerical errors. We describe the evaluation of three
different algorithms for our new magnetic DI code INVERS10. We also
show the first results of numerical experiments made with the new code.

---------------------------------------------------------
Title: EU III identification and EU abundance in cool CP stars
Authors: Ryabchikova, T.; Piskunov, N.; Savanov, I.; Kupka, F.
1998CoSka..27..359R Altcode: 1998astro.ph..5206R
We report the first identification of the Eu III lambda 6666.317
line in optical spectra of CP stars. This line is clearly present in
the spectra of HR 4816, 73 Dra, HR 7575, and beta CrB, while it is
marginally present or absent in spectra of the roAp stars alpha Cir,
gamma Equ, BI Mic, 33 Lib, and HD 24712.

---------------------------------------------------------
Title: Linear spectropolarimetry of AP stars: a new degree of
constraint on magnetic structure
Authors: Wade, G. A.; Donati, J. -F.; Mathys, G.; Piskunov, N.
1998CoSka..27..436W Altcode: 1998astro.ph..5069W
We present preliminary results from a programme aimed at acquiring
linear spectropolarimetry of magnetic A and B stars. Linear polarization
in the spectral lines of these objects is due to the Zeeman effect,
and should provide detailed new information regarding the structure
of their strong magnetic fields. To illustrate the impact of these
new data, we compare observed circular and linear polarization line
profiles of 53 Cam with the profiles predicted by the magnetic model
by Landstreet. Linear polarization in the spectral lines of all
stars studied is extremely weak; in most cases, below the threshold
of detectability even for very high SNRs. In order to overcome this
problem, we employ the Least-Squares Deconvolution (LSD) multi-line
analysis technique in order to extract low-noise mean line profiles
and polarization signatures from our echelle spectra. Tests show
that these mean signatures can be modelled as real spectral lines,
and have the potential to lead to high-resolution maps of the magnetic
and chemical abundance surface distributions.

---------------------------------------------------------
Title: Multi-element Doppler imaging of kappa PSC
Authors: Piskunov, N.; Stempels, H. C.; Ryabchikova, T. A.;
Malanushenko, V.; Savanov, I.
1998CoSka..27..482P Altcode: 1998astro.ph..5250P
kappa Psc (HD 220825) is a typical Chromium Ap star that happens to
have optimal parameters for Doppler imaging (DI). Its short rotational
period of less than 2 days, rotational velocity of approx. 40 km/s, and
a moderate inclination of the rotational axis put modest requirements
on spectroscopic observations. Anomalies of iron peak elements are
clearly present, but small enough to cause significant deviations from
model atmospheres with scaled solar abundances. We applied DI to kappa
Psc once before, determining the distribution of Cr. However, due to
strong blending of Fe, the image was based on two short (approx. 2 A)
spectral intervals, dominated by Cr lines. Since the first paper we
obtained additional spectra and developed a new code that allows to
perform multi-element DI and thus to use larger spectral interval(s). We
demonstrate the abilities of the new code and present new maps of Cr
and Fe. A much larger time base allowed us to improve the rotational
period of kappa Psc as well.

---------------------------------------------------------
Title: A Fiber-Linked Four Stokes-Parameter Polarimeter for the
SOFIN Spectrometer on the Nordic Optical Telescope
Authors: Pettersson, B.; Stempels, E.; Piskunov, N.
1998ASPC..152..343P Altcode: 1998fopa.proc..343P
No abstract at ADS

---------------------------------------------------------
Title: Observational Constraints on the Dynamo in Flare Stars
Authors: Valenti, Jeff A.; Johns-Krull, Christopher M.; Piskunov,
Nikolai
1998ASPC..154.1357V Altcode: 1998csss...10.1357V
There is increasing evidence that the dynamo mechanism in dMe flare
stars differs from the alphaOmega dynamo believed to operate in
the Sun. We review existing observational constraints on the dynamo
and then present new constraints. In particular, we show that the
magnetic field on Gliese 729 has been constant for 1.5 years, despite
large variations in Hα equivalent width. This has implications for
chromospheric heating and the existence of stellar cycles in flare
stars. We also present preliminary polarimetry of AD Leo, demonstrating
the the field is not globally organized. We discuss these results in
the context of existing dynamo models.

---------------------------------------------------------
Title: INVERS10: A New Code for Magnetic Doppler Imaging
Authors: Piskunov, N.
1998ASPC..154.2029P Altcode: 1998csss...10.2029P
We present a new Magnetic Doppler Imaging computer code designed to
simultaneously reconstruct both the 3D structure of magnetic fields and
the temperature structure of active regions on the surfaces of late-type
stars. We show results from numerical experiments and demonstrate that
the full set Stokes parameters is needed for proper reconstruction of
the magnetic field vector.

---------------------------------------------------------
Title: The Vienna Atomic Line Database : Present State and Future
Development
Authors: Ryabchikova, T. A.; Piskunov, N. E.; Kupka, F.; Weiss, W. W.
1997BaltA...6..244R Altcode: 1997OAst....6..244R
We describe the main structure of the Vienna Atomic Line Database,
the tools provided for the users and the statistics of its use in
the last two years. Our plans for future developments of the database
are discussed.

---------------------------------------------------------
Title: Local Interstellar Medium Properties and Deuterium Abundances
for the Lines of Sight toward HR 1099, 31 Comae, β Ceti, and β
Cassiopeiae
Authors: Piskunov, Nikolai; Wood, Brian E.; Linsky, Jeffrey L.;
Dempsey, Robert C.; Ayres, R.
1997ApJ...474..315P Altcode:
We analyze Goddard High-Resolution Spectrograph data to infer the
properties of local interstellar gas and the deuterium/hydrogen (D/H)
ratio for lines of sight toward four nearby late-type stars--HR 1099,
31 Comae, β Ceti, and β Cassiopeiae. The data consist of spectra
of the hydrogen and deuterium Lyα lines, and echelle spectra of the
Mg II h and k lines toward all stars except β Cas. Spectra of the RS
CVn-type spectroscopic binary system HR 1099 were obtained near opposite
quadratures to determine the intrinsic stellar emission line profile and
the interstellar absorption separately. Multiple-velocity components
were found toward HR 1099 and β Cet. The spectra of 31 Com and β
Cet are particularly interesting because they sample lines of sight
toward the north and south Galactic poles, respectively, for which H I
and D I column densities were not previously available. The north
Galactic pole appears to be a region of low hydrogen density like the
“interstellar tunnel” toward ɛ CMa. The temperature and turbulent
velocities of the local interstellar medium (LISM) that we measure
for the lines of sight toward HR 1099, 31 Com, β Cet, and β Cas are
similar to previously measured values (T ~ 7000 K and ξ = 1.0-1.6 km
s-1). The deuterium/hydrogen ratios found for these lines
of sight are also consistent with previous measurements of other short
lines of sight, which suggest D/H ~ 1.6 × 10-5. In contrast,
the Mg abundance measured for the β Cet line of sight [implying a
logarithmic depletion of D(Mg) = +0.30 +/- 0.15] is about 5 times larger
than the Mg abundance previously observed toward α Cen, and about 20
times larger than all other previous measurements for the LISM. These
results demonstrate that metal abundances in the LISM vary greatly
over distances of only a few parsecs. Based on observations with
the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope
Science Institute, which is operated by the Association of Universities
for Research in Astronomy, Inc., under NASA contract NAS5-26555.

---------------------------------------------------------
Title: Surface distribution of chromium on the CP2 star HD 220825
(κ Psc)
Authors: Ryabchikova, T. A.; Pavlova, V. M.; Davydova, E. S.; Piskunov,
N. E.
1996AstL...22..822R Altcode: 1996AstL...22..821R; 1996PAZh...22..917R
No abstract at ADS

---------------------------------------------------------
Title: Spectroscopy made easy: A new tool for fitting observations
with synthetic spectra.
Authors: Valenti, J. A.; Piskunov, N.
1996A&AS..118..595V Altcode:
We describe a new software package that may be used to determine stellar
and atomic parameters by matching observed spectra with synthetic
spectra generated from parameterized atmospheres. A nonlinear least
squares algorithm is used to solve for any subset of allowed parameters,
which include atomic data (log gf and van der Waals damping constants),
model atmosphere specifications (T_ eff_, logg), elemental abundances,
and radial, turbulent, and rotational velocities. LTE synthesis
software handles discontiguous spectral intervals and complex atomic
blends. As a demonstration, we fit 26 FeI lines in the NSO Solar Atlas
(Kurucz et al. 1984), determining various solar and atomic parameters.

---------------------------------------------------------
Title: The Three-Dimensional Structure of the Local Interstellar
Medium
Authors: Linsky, J. L.; Piskunov, N.; Wood, B. E.
1996AAS...188.4407L Altcode: 1996BAAS...28..892L
We construct the first detailed three-dimensional models of the Local
Interstellar Cloud (LIC) and the total amount of warm gas in the
local interstellar medium (LISM) within 10 parsecs of the Sun. These
models are based on the amount of neutral hydrogen gas deduced (a) from
measurements of the deuterium column density toward nearby late-type
stars, obtained from the analysis of Hubble Space Telescope spectra,
and (b) from the spectra of hot white dwarf stars measured with the
Extreme Ultraviolet Explorer satellite. The two methods give consistent
results. We find that the LIC is flattened in the Galactic plane and
that the hydrogen column densities are very similar for stars located
in the sky within 12(deg) , indicating the angular scale of the gas
close to the Sun. The direction of minimum hydrogen absorption through
the LISM is near Galactic longitude l=262(deg) and latitude b=+22(deg)
. This work is supported by NASA Grant S-56460-D.

---------------------------------------------------------
Title: M-Dwarfs: Molecules and Magnetic Fields
Authors: Valenti, J. A.; Johns-Krull, C. M.; Piskunov, N.
1996AAS...188.3206V Altcode: 1996BAAS...28..867V
At McDonald Observatory, we recently obtained echelle spectra
(R=120,000; S/N&gt;100) of several M0V to M5V stars. Interpreting
these spectra in detail has been challenging, but also quite
fascinating. From an analysis standpoint, the largest perturbation from
a solar analogy arises because of the prevalence of molecules in the
atmosphere. Fortunately, Allard &amp; Hauschildt (1995) have constructed
and continue to refine theoretical atmospheres, which include the
effects of molecules. Meanwhile, Jorgensen (1994) has recently compiled
extensive lists of molecular line data. These important contributions,
available in an electronic format, allowed us to synthesize spectra
using standard LTE radiative transfer techniques. By comparing these
synthetic spectra with selected wavelength regions in our observed
spectra, we were able to correct the electronic oscillator strength for
the epsilon band of TiO, and also to refine the molecular constants for
the gamma band. In addition, we hope to assess how well the theoretical
atmospheres for various effective temperatures are able to reproduce
observed depths of TiO lines. Active M dwarfs have relatively large
flare luminosities and X-ray surface fluxes, implying magnetic fields
and/or filling factors well above solar. Saar &amp; Linsky (1985)
provided the first direct evidence for 4 kG fields covering the
surface of an M dwarf. We recently confirmed this result by detecting
Zeeman split sigma --components in the FeI line at 8468.40 Angstroms
(Johns--Krull &amp; Valenti 1996). This demonstration was primarily
empirical: the extended wings seen in the FeI line are not seen in
spectra of inactive M dwarfs, whereas the neighboring TiO lines are
all well matched, ruling out most nonmagnetic explanations. We also
determined magnetic field strength and filling factor by modeling the
ratio of active and inactive spectra, which is less sensitive to model
uncertainties and molecular blends. We are implementing a Feautrier
scheme to accurately synthesize spectra when both molecules and magnetic
fields are important. We hope to have available for discussion initial
results from a new analysis of active M dwarfs.

---------------------------------------------------------
Title: Introduction
Authors: Lester, J. B.; Piskunov, N. E.
1996ASPC..108..159L Altcode: 1996mass.conf..159L
No abstract at ADS

---------------------------------------------------------
Title: Spectroscopy Made Easy
Authors: Valenti, J. A.; Piskunov, N. E.
1996ASPC..108..175V Altcode: 1996mass.conf..175V
No abstract at ADS

---------------------------------------------------------
Title: Doppler imaging of eclipsing binaries
Authors: Piskunov, N.
1996IAUS..176...45P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Structure of VALD
Authors: Piskunov, N. E.
1996ASPC..108..307P Altcode: 1996mass.conf..307P
No abstract at ADS

---------------------------------------------------------
Title: The Chromosphere and Wind of zeta Aurigae
Authors: Bennett, P. D.; Brown, A.; Harper, G. M.; Piskunov, N.;
Griffin, R. E. M.
1995AAS...18710304B Altcode: 1995BAAS...27.1431B
The zeta Aurigae binary systems consist of evolved supergiants which
eclipse their early-type main sequence companions. These binaries have
been extensively studied because of their potential for probing the
outer atmospheric structure of the evolved late-type primary. This
technique is extremely advantageous in the ultraviolet where the cool
primary contributes little flux. To this end, we have undertaken an
analysis of the chromosphere and wind of the prototype system, zeta
Aurigae, and we graphically demonstrate the resulting model by means
of a video presentation. Our atmospheric model of the chromosphere
and wind of the primary star of zeta Aurigae (K4 Ib + B5 V) is based
on Cycle 2 and recent Cycle 5 observations obtained with the Goddard
High Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope,
and on archival IUE and optical spectra. The models were iterated
to reproduce the observed circumstellar absorption line curves of
growth, and individual absorption profiles, for various projected
heights above the limb of the K supergiant. To conveniently show the
variation of typical line profiles computed with this model, we have
prepared a video that follows the zeta Aurigae binary system through a
complete orbit. We display several windows showing a perspective view
of the system from a vantage point above the orbital plane, the view
as seen from earth (nearly edge-on, i=87.3(deg) ), and the behavior of
absorption lines formed in the chromosphere and wind of zeta Aurigae as
a function of orbital phase. Support for this work was provided by NASA
through grants GO-3626-91A and GO-06069.01-94A from the Space Telescope
Science Institute, which is operated by the Association of Universities
for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

---------------------------------------------------------
Title: VALD: The Vienna Atomic Line Data Base.
Authors: Piskunov, N. E.; Kupka, F.; Ryabchikova, T. A.; Weiss, W. W.;
Jeffery, C. S.
1995A&AS..112..525P Altcode:
The "Vienna Atomic Line Data Base" (VALD) consists of a set of
critically evaluated lists of astrophysically important atomic
transition parameters and supporting extraction software. VALD contains
about 600000 entries and is one of the largest collections of accurate
and homogeneous data for atomic transitions presently available. It
also includes specific tools for extracting data for spectrum synthesis
and model atmosphere calculations. The different accuracies of data
available in the literature made it necessary to introduce a ranking
system and to provide a flexible method for extracting the best possible
set of atomic line parameters for a given transition from all the
available sources. The data base is presently restricted to spectral
lines which are relevant for stars in which the LTE approximation is
sufficient and molecular lines do not have to be taken into account. The
provision was made that these requirements should not restrict the
general design of VALD and the possibility of future expansion. In
this paper we describe the structure of VALD, the available data sets
and specific retrieval tools. The electronic-mail interface (VALD-EMS)
created to allow remote access to VALD is also described. Both users
and producers of atomic data are invited to explore the database,
and to collaborate in improving and extending its contents.

---------------------------------------------------------
Title: The HeI surface distribution of the CP2 star CU Virginis.
Authors: Hiesberger, F.; Piskunov, N.; Bonsack, W. K.; Weiss, W. W.;
Ryabchikova, T. A.; Kuschnig, R.
1995A&A...296..473H Altcode:
Based on Coude spectra obtained with the 2.24-m telescope at MKO, we
derive a map of the surface distribution of helium for the B9pSi star
CU Vir. The helium abundance varies by more than one order of magnitude
over the surface of this star and is concentrated in one large spot and
a second, less pronounced, spot. This pattern is in anti-phase to the
silicon surface distribution and is similar to what we have found for
ET And, which is another Si-star. We compare our observed equivalent
width measurements and synthetic ones, which we have derived from our
map, with previously published data and can corroborate the long-term
stability of the spots. CU Vir is the second CP2 star, for which a
helium surface map is available.

---------------------------------------------------------
Title: The atmosphere of the peculiar binary system ET Andromedae.
Authors: Kuschnig, R.; Ryabchikova, T.; Piskunov, N.; Weiss, W. W.;
Lecontel, J. M.
1995A&A...294..757K Altcode:
High spectral resolution, high signal-to-noise OHP spectra which
cover the range from 4000A to 7500A were used to derive abundances
for ET And. An extreme overabundance of silicon by nearly 100 times
of the solar value corroborates the Si-star classification. We find
also enhanced abundances for iron-peak and rare-earths elements,
which is typical for this group of CP stars. The deficiency of He
(1/30 of the solar value), and to a lesser extent of Mg and C, is
remarkable. Based on an estimate for R/Rsun_, derived
from geometric arguments, and the measured interstellar Nai lines we
conclude that ET And probably still has not evolved significantly from
the main sequence. We present arguments, why some earlier luminosity
determinations seem to be incorrect.

---------------------------------------------------------
Title: The Vienna Atomic Line Data-Base
Authors: Piskunov, N. E.; Kupka, F.; Ryabchikova, T. A.; Weiss, W. W.;
Jeffery, C. S.
1995ASPC...81..610P Altcode: 1995lahr.conf..610P
No abstract at ADS

---------------------------------------------------------
Title: Ap-star mapping: He, Mg, Si, and Fe surface distributions on
the CP2 star CU Virginis
Authors: Kuschnig, R.; Ryabchikova, T.; Piskunov, N. E.; Weiss, W. W.
1995IAUS..176P.135K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Progress in surface imaging
Authors: Piskunov, N. E.; Rice, J. B.
1995BCrAO..91..176P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ap-star mapping: Fe and Cr abundance distribution on the
surface of HD 153882
Authors: Ryabchikova, T.; Kuschnig, R.; Piskunov, N. E.; Pavlova, V.
1995IAUS..176P.132R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Providing a Common GUI to Image Processing Tasks under pcIPS
Authors: Smirnov, O. M.; Piskunov, N. E.
1995ASPC...77..133S Altcode: 1995adass...4..133S
No abstract at ADS

---------------------------------------------------------
Title: Spectrum variability of ET Andromedae: SI and He surface
mapping.
Authors: Piskunov, N.; Ryabchikova, T. A.; Kuschnig, R.; Weiss, W. W.
1994A&A...291..910P Altcode:
ETAnd is a silicon star with a rotation period of 1.62d and the visible
component of a binary system with an orbital period of 48.3d. We
present abundance maps for silicon and helium, based on OHP-AURELIE
spectra, and demonstrate that silicon and helium are concentrated in a
belt-like structure along the magnetic equator. Surface regions with a
silicon overabundance are correlated with helium underabundance. In the
framework of diffusion theory, this pattern implies that a magnetic
field configuration of ETAnd which favours the elevation of Si,
simultaneously causes He to sink. In addition, we comment on the
significance of Doppler mapping of CP stars for a correct abundance
determination and on implications to pulsation mode identifications. We
discuss our upper limit for short time-scale radial velocity variations
of 1.4km/s, which contrasts to 4km/s, as was claimed in the literature
with a period of 4.8^h^.

---------------------------------------------------------
Title: The detectability of cool polar caps on late type stars.
Authors: Piskunov, N.; Wehlau, W. H.
1994A&A...289..868P Altcode:
From spectral line profiles the presence of a cool polar cap has been
inferred for several late-type stars; for some other similar stars
the absence of a cool polar cap has been suggested. In addition, it
would be surprising if a star with a cool region at one rotational
pole did not have a similar cool region at the other pole. To test the
detectability of cool polar caps on late type stars we have computed
the effect such cool spots would have on the profile of the Ca I 6439
A. While a cool cap at the visible pole may be detected, the presence
of another equivalent cap at the other pole cannot be detected with
current techniques.

---------------------------------------------------------
Title: Surface imaging of stars.
Authors: Piskunov, N.
1994JRASC..88..254P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Astrophysical determination of optical oscillator strengths
for TI II.
Authors: Ryabchikova, T. A.; Hill, G. M.; Landstreet, J. D.; Piskunov,
N.; Sigut, T. A. A.
1994MNRAS.267..697R Altcode:
An internally consistent set of relative oscillator strengths for
109 spectral lines of Ti II in the range 3800-5500 Å has been
derived. These oscillator strengths have been obtained by combining
available laboratory data and theoretical calculations with new
astrophysical oscillator strengths determined from both published
photographic equivalent width lists and spectral synthesis of a
number of available Reticon spectra of several sharp-lined stars. The
accuracy of our astrophysical oscillator strengths has been tested
by determining astrophysical gf-values for a number of lines of Fe
II by the same methods. The Ti II data have been normalized to the
astrophysical oscillator strengths of Kostyk &amp; Orlova, which also
places them essentially on the scale of Danzmann &amp; Kock, one of
the most recent and extensive experimental data sets. It appears that
the accuracy of the relative gf-values in our final mean list for Ti
II is typically about 0.08 dex. The absolute normalization is believed
to be secure to within about 0.15 dex.

---------------------------------------------------------
Title: Simultaneous SPOT and Chromosphere Maps of FK Comae
Authors: Piskunov, N. E.; Huenemoerder, D.; Saar, S. H.
1994ASPC...64..658P Altcode: 1994csss....8..658P
Maps of the local T_eff and chromospheric intensity (from He I D3)
from a surface imaging analysis of 51 echelle spectra of FK Comae show
a complex relationship between spots and activity.

---------------------------------------------------------
Title: Surface Imaging of Spotted Stars
Authors: Piskunov, N.
1994cpms.conf...53P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: PC-based Astronomical Image Processing with pcIPS
Authors: Smirnov, O. M.; Piskunov, N. E.
1994ASPC...61..245S Altcode: 1994adass...3..245S
Modern 486-based PCs are fast enough for many serious image processing
applications, and inexpensive enough even for amateur astronomers. Our
pcIPS image processing system runs on these platforms and satisfies
a broad range of data analysis needs, while providing maximum
expandability. It supports large format 1D and 2D images in any numeric
type, from 8-bit integer to 64-bit floating point. pcIPS includes a set
of visualization tools as part of an intuitive graphical user interface
that employs buttons, pop-up menus, and a mouse. It is extremely
expandable, because all of the image processing functionality is
provided by external modules ( applications ), with new ones constantly
being developed. The basic application package includes ones for
elementary arithmetics and statistics, geometric transformations, and
import/export of various data formats (FITS, plain ASCII, Photometrics,
binary, GIF, etc.); specialized astronomy-oriented packages will be
demonstrated. An API lets the user create his own applications in
C and FORTRAN. The demo will show the latest version of the system,
as well as some of its recently-created applications. The newest of
them is a port of the DAOPHOTII stellar photometry program, and a
Fourier analysis package. A CCD/Echelle processing package (location
of echelle orders, geometric correction and extraction of orders,
flat field correction, etc.) and a Spectral package (generation of
dispersion curve, continuum fitting, wavelength calibration, multiple
simultaneous line profile fits) will also be shown.

---------------------------------------------------------
Title: Progress in surface imaging.
Authors: Piskunov, N. E.; Rice, J. B.
1994IzKry..91..208P Altcode:
Surface imaging of stars from the profiles of spectral line became
an important tool in modern astrophysics. It is applied for mapping
the distribution of chemical elements on Ap stars and temperature on
late-type stars. Magnetic field maps appear as well as high quality
polarization observations will be available. The authors review the
latest achievements in all components of surface imaging which resulted
in more reliable and detailed maps.

---------------------------------------------------------
Title: Multiepoch Magnetic Surface Images of LQ Hya
Authors: Saar, S. H.; Piskunov, N. E.; Tuominen, I.
1994ASPC...64..661S Altcode: 1994csss....8..661S
We study several epochs of magnetic surface images of the active single
dwarf LQ Hya to explore the surface differential rotation (SDR) rate
and the correlation between magnetic flux Phi_B and T_eff.

---------------------------------------------------------
Title: Techniques for Surface Imaging of Stars
Authors: Piskunov, N. E.; Rice, J. B.
1993PASP..105.1415P Altcode:
Surface imaging of stars from the profiles of spectral lines, has
become an important tool in modern astrophysics. It is presently used
for mapping the distribution of chemical elements on Ap stars and the
variation in temperature over the surface of late-type stars. Magnetic
field maps will be produced as soon as high quality polarization
observations are available. Recently imaging techniques have been
developed for application to eclipsing binary stars. In this paper we
review the improvements we have found to result in more reliable and
detailed maps in all aspects of surface imaging. (SECTION: Stars)

---------------------------------------------------------
Title: Surface imaging of eclipsing binary stars. I. Techniques.
Authors: Vincent, A.; Piskunov, N. E.; Tuominen, I.
1993A&A...278..523V Altcode:
Surface (Doppler) imaging techniques for mapping the temperature
distribution of a single star are generalized to the case of an
eclipsing spectroscopic binary. In this paper we study three main
questions, crucial for further application of the techniques. We
found that the method described in this paper can be successfully
used for imaging eclipsing binary systems. The resulting map is more
sensitive to the errors in the parameters of the system than is the
case of a single star. Characteristic distortions of the map can be
used as indicators for fine tuning of some of the parameters. We also
found that a good phase coverage of the observations is most important
for reducing the artificial equatorial symmetry, typical for the line
profile inversion when used for high inclination binary systems.

---------------------------------------------------------
Title: Image Processing on Your Desktop with pcIPS
Authors: Smirnov, O. M.; Piskunov, N. E.
1993IAPPP..53...16S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: PcIPS 2.0: Powerful Multiprofile Image Processing Implemented
On PCs
Authors: Smirnov, O. M.; Piskunov, N. E.
1993ASPC...52..259S Altcode: 1993adass...2..259S
No abstract at ADS

---------------------------------------------------------
Title: A New Programming Metaphor For Image Processing Procedures
Authors: Smirnov, O. M.; Piskunov, N. E.
1993ASPC...52..208S Altcode: 1993adass...2..208S
No abstract at ADS

---------------------------------------------------------
Title: Magnetic Surface Images of the BY DRA Star HD 82558
Authors: Saar, S. H.; Piskunov, N. E.; Tuominen, I.
1992ASPC...26..255S Altcode: 1992csss....7..255S
We present preliminary results of a new analysis method applied
to spectra of the BY Dra star HD 82558. We invert a time series of
unpolarized line profiles with different Lande g_eff values to derive
both temperature and magnetic field maps of the star. We find strong
fields (B &gt; 2 kG) near cool spots and weaker fields elsewhere,
with &lt;B&gt; ~ 1 kG.

---------------------------------------------------------
Title: PC-IPS: Interactive System For Astronomical Image Processing
Authors: Smirnov, O. M.; Piskunov, N. E.; Afanasyev, V. P.; Morozov,
A. I.
1992ASPC...25..344S Altcode: 1992adass...1..344S
No abstract at ADS

---------------------------------------------------------
Title: SYNTH - a code for rapid spectral synthesis
Authors: Piskunov, N. E.
1992pess.conf...92P Altcode: 1992stma.conf...92P
No abstract at ADS

---------------------------------------------------------
Title: Doppler imaging of hig-latitude SPOT activity on HD 26337.
Authors: Strassmeier, K. G.; Rice, J. B.; Wehlau, W. H.; Vogt, S. S.;
Hatzes, A. P.; Tuominen, I.; Piskunov, N. E.; Hackman, T.; Poutanen, M.
1991A&A...247..130S Altcode:
Three different versions of the Doppler-imaging technique are applied
to the spotted RS CVn-type binary HD 26337 = Ei Eri. New high-resolution
high-S/N spectroscopy was obtained along with simultaneous BV photometry
during 1988. Images were generated independently by three separate
groups using different versions of the Doppler-imaging technique but the
same data. All maps from Ca I 6439 A showed a cool asymmetric spot at
the pole or at high latitudes generally surrounding the rotation pole
and also some smaller equatorial spots. The maps from Fe I exhibit
detailed differences to the maps from Ca I. The equatorial features
were found to change on short time-scales (weeks). It is inferred that
the polar spot is short-lived (years) but changes its appearance on the
same several-week time-scale. Simultaneous and contemporary broad-band
photometry was found to be crucial as additional data in the mapping
procedure and as a reliability test of the Doppler-imaging solution.

---------------------------------------------------------
Title: The second generation automated system for spectrum processing
in the Astronomical council of the Academy of sciences of USSR
Authors: Kulkova, L. I.; Piskunov, N. E.; Svyatoslavskij, N. L.
1991NInfo..70...56K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Art of Surface Imaging
Authors: Piskunov, N. E.
1991LNP...380..309P Altcode: 1991sacs.coll..309P; 1991IAUCo.130..309P
We intend to analyze the reliability of surface imaging of stars based
on high resolution spectroscopy and the technique of inverse problem
solution. Both astrophysical and mathematical aspects including
different regularization methods are reviewed. The influence of
the different factors on the resulting map is discussed and it is
shown that the simultaneous use of different kinds of observational
data (spectroscopy, photometry, polarimetry etc.) is very useful in
providing additional constraints for the solution. The recent results
in the surface imaging of Cp- and late-type stars show the way for
further progress: the use of more adequate mathematical description of
the stellar atmosphere and the simultaneous consideration of various
surface inhomogeneities.

---------------------------------------------------------
Title: Surface Imaging of Ei-Eridani
Authors: Hackman, T.; Piskunov, N. E.; Poutanen, M.; Strassmeier,
K. G.; Tuominen, I.
1991LNP...380..321H Altcode: 1991IAUCo.130..321H; 1991sacs.coll..321H
We present maps of the temperature distribution on the spotted
RS CVn-type binary EI Eri (HD 26337), obtained by means of the
surface imaging technique described in the Colloquium (Piskunov,
1991). Images were calculated for two separate lines for two epochs
of observation. For one epoch we also calculated an image using a
blend of several lines. The reliability of the maps is confirmed by
comparing the simultaneous photometric observations with the light
curves calculated from the temperature maps.

---------------------------------------------------------
Title: Proton and triton momentum distributions from4He
fragmentation at relativistic energies
Authors: Ableev, V. G.; Dshemuchadse, S. V.; Dimitrov, C.; Kobushkin,
A. P.; Naumann, B.; Naumann, L.; Nomofilov, A. A.; Penchev, L.;
Piskunov, N. M.; Sharov, V. I.; Sitnik, I. M.; Strokovsky, E. A.;
Strunov, L. N.; Tesch, S.; Zaporozhets, S. A.
1990FBS.....8..137A Altcode:
The 0° differential cross sections of the12C(4He,
p) and12C(4He, t) reactions have been measured at
beam momenta of 4.52 and 2.69 GeV/ c/nucleon, respectively. The proton
and triton momentum distributions in4He are extracted from
the cross sections using a relativistic impulse approximation. Some
theoretical models based on realistic N-N potentials are examined for
our data.

---------------------------------------------------------
Title: Mapping stellar surfaces from spectra of medium resolution
Authors: Piskunov, N. E.; Wehlau, W. H.
1990A&A...233..497P Altcode:
The use of spectra with resolutions of 6, 9, 12, and 15 km/s to
produce maps of abundance inhomogeneities on the surfaces of stars
is studied. It is assumed that the spectra have a high SNR, are free
from blends, and that the inclination of the axis of rotation and
the locations of surface features are favorable. Numerical studies of
the Fe II 4923 A line showed that, for v sin i greater than about 30
km/s, good maps of surface features can be expected from spectra with
resolutions of 6 km/s or better.

---------------------------------------------------------
Title: Surface imaging of late-type stars.
Authors: Piskunov, N. E.; Tuominen, I.; Vilhu, O.
1990A&A...230..363P Altcode:
The basic principles of stellar surface imaging techniques are
discussed, and two ways of regularizing this ill-posed inverse problem
are compared. Maximizing the information entropy means that minimum
correlation between different points at the stellar surface should
be expected, while the use of a Tikhonov regularization functional
leads to the smoothest possible solution. Physical conditions in the
stellar surface layers may favor the latter method, and the present
simulation experiment shows that it does not produce small size,
high contrast features below the spatial and temporal resolution of
the data, which is typical of maximum entropy images. The technique
is also illustrated by applying it to the FK Comae-type star HD 32918.

---------------------------------------------------------
Title: The surface imaging of the stars.
Authors: Piskunov, N. E.
1990MmSAI..61..577P Altcode:
A general approach to the surface imaging of stars based on high
resolution spectroscopy and the technique of inverse problem solution
are formulated. Both astrophysical and mathematical aspects including
different regularization methods are reviewed. The influence of
the different factors on the reliability of the resulting map is
discussed. It is shown that the simultaneous use of different kinds of
observational data (spectroscopy, photometry, and polarimetry) might be
very useful in providing additional constraints for the solution. The
recent results in the surface imaging of Cp- and late-type stars show
the way for further progress: the use of a more adequate mathematical
description of stellar atmospheres and the simultaneous consideration
of various surface inhomogeneities.

---------------------------------------------------------
Title: Surface Imaging of Giant Stars and Nonlinear Dynamos
Authors: Tuominen, I.; Piskunov, N. E.; Moss, D.; Brandenburg, A.
1990ASPC....9...73T Altcode: 1990csss....6...73T
Recent results of photometric cycles and surface images of active
giants are discussed in terms of nonlinear 3D mean-field dynamos. The
existence of mixed parity solutions with periodic and quasi-periodic
time dependence is suggestive for explaining the nonaxisymmetric
surface patterns observed on active giant stars.

---------------------------------------------------------
Title: Preliminary results of new observations of NGC 6888.
Authors: Bochkarev, N. G.; Lozinskaya, T. A.; Pravdikova, V. V.;
Sitnik, T. G.; Piskunov, N. N.
1988TarOT..89..168B Altcode:
Einstein Observatory X-ray data and new monochromatic Fabry-Perot
interferometric observations are presented for nebula NGC 6888 around
the WN6 star HD 192163. Temperature and density stratification and
large-scale asymmetry of the nebula are discussed.

---------------------------------------------------------
Title: Abundance analysis of Hg-Mn star ϕ Herculis
Authors: Ryabchikova, T. A.; Piskunov, N. E.
1988mast.conf..124R Altcode:
Method and main results of abundance analysis of φ Her are presented.

---------------------------------------------------------
Title: Abundance Analysis of the Mercury-Manganese Star Phi Herculis
Authors: Ryabchikova, T. A.; Piskunov, N. E.
1988eaa..conf...93R Altcode:
Contents: 1. Introduction. 2. Spectra reductions. 3. Stellar
radial velocity and line identifications. 4. Model atmosphere
parameters. 5. Computer code for line profiles calculation. 6. The
determination of metal abundances and microturbulent
velocity. 7. Conclusions.

---------------------------------------------------------
Title: The estimation of 53 Cam magnetic field value by means of
spectral line width analysis
Authors: Glagolevskij, Yu. V.; El'Kin, V. G.; Romanyuk, I. I.;
Piskunov, N. E.
1988mast.conf...32G Altcode:
Systematical studies of 53 Cam spectral lines widening were carried
out in order to find the possible structural features and the mean
value of the surface magnetic field.

---------------------------------------------------------
Title: Service programmes expanding possibilities of programming in
FORTRAN language in OS ES
Authors: Lukin, V. Yu.; Piskunov, N. E.
1986NInfo..59...89L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: General principles of computer image processing
Authors: Lukin, V. Yu.; Mit'kin, K. N.; Piskunov, N. E.
1986NInfo..59...99L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Estimation of Stellar Surface Magnetic Fields by the Curve-Of
Method
Authors: Riabchikova, T. A.; Piskunov, N. E.
1986ASSL..125...45R Altcode: 1986umss.conf...45R; 1986umss.proc...45R; 1986IAUCo..90...45R
The curve-of-growth method of estimating the stellar surface magnetic
fields is applied to six Ap stars of different temperatures and
one normal (or metallic-line) star, Sigma Aqr. The values of H(s)
determined by the curve-of-growth technique are in good agreement with
those obtained by the photometric method.

---------------------------------------------------------
Title: An automated astronomical image processor
Authors: Grishin, M. P.; Kurbanov, S. M.; Pakhomov, S. V.; Piskunov,
N. E.; Sviatoslavskii, N. L.
1985SvAL...11..335G Altcode:
The design of an automatic image processing system which is based
on an AMD-1 microdensitometer is described. The system contains an
optical section with a dual-beam design, a measurement unit, and a
calibration unit. The measurement unit is composed of illuminating
and projection microscopes, illumination and measurement diaphragms,
and a photodetector, and the calibration unit has a light guide and
a reference photodetector. The image scanning, which is conducted
with a two-coordinate mechanically controlled sweep, is examined. The
system is also capable of reproducing extracted halftone information
on photographic film. The system has a photometric accuracy of 1-2
percent, positional accuracy of 5 microns, and an optical density range
of 0-4 D. The potential error factors which include scattering with the
optics, nonlinearity, drift, and the operation speed of the electronic
photometry channel are analyzed. The image processing system is applied
to stellar spectra and the optical identification of radio sources.

---------------------------------------------------------
Title: Investigation of the AP star alpha2 CVn magnetic field geometry
from circular polarization profiles of metallic lines.
Authors: Glagolevskij, Yu. V.; Piskunov, N. E.; Khokhlova, V. L.
1985PAZh...11..371G Altcode:
Circular-polarization profiles of Fe II, Ti II lines are processed by
solving the inverse problem to yield a model for the magnetic field
geometry of the Ap star Alpha(2) CVn, allowing for the nonuniform
distribution of elements over the stellar surface. The results are
compared with other authors' models deduced by interpretation of
effective-field curves.

---------------------------------------------------------
Title: Magnetic Field Geometry of ALPHA-2-CANUM-VENATICORUM Derived
from Circular Polarization Profiles of Metal Lines
Authors: Glagolevskii, Y. V.; Piskunov, N. E.; Khokhlova, V. L.
1985SvAL...11..154G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The magnetic field geometry of AP stars - A solution algorithm
Authors: Piskunov, N. E.
1985PAZh...11...44P Altcode:
A solution algorithm is obtained for calculating the magnetic field
geometry of an Ap star based on the circular and linear polarization of
its spectral lines. The algorithm is based on the conjugate gradient
of Fletcher and Reeves (1964). The magnetic field geometry of an Ap
star with magnetic field strength in the range 2500-5000 gauss was
calculated numerically, in order to assess the efficiency of the
algorithm. It is shown that the computed parameters were free from
error due to variations in rotational velocity. Some advantages of
the present method are discussed in comparison with the conventional
practice of interpreting effective-field curves for Ap stars.

---------------------------------------------------------
Title: The Magnetic Field Geometry of Ap-Stars - a Solution Algorithm
Authors: Piskunov, N. E.
1985SvAL...11...18P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Automated System for Astronomical Image Processing
Authors: Grishin, M. P.; Kurbanov, S. M.; Pakhomov, S. V.; Piskunov,
N. E.; Svyatoslavskij, N. L.
1985PAZh...11..793G Altcode:
A system for astronomical image processing based on the
microdensitometer AMD-1BC is described. Its general technical
characteristics are given in comparison with other similar systems. The
distortions due to the image reading device are described. Results
of the experimental studying of the system are given. The application
fields for the system are specified.

---------------------------------------------------------
Title: Linear-polarization line profiles as an indicator of the
magnetic field geometry of AP stars
Authors: Piskunov, N. E.; Khokhlova, V. L.
1984PAZh...10..449P Altcode:
Linear polarization profiles for normal Zeeman triplet structure of
spectral lines where calculated in the framework of the oblique rotator
model. It is shown that the orientation of magnetic and rotation axes
can be uniquely derived from the observed phase variation of linear
polarization profiles.

---------------------------------------------------------
Title: Linear Polarization Line Profiles as an Indicator of the
Magnetic Field Geometry of Ap-Stars
Authors: Piskunov, N. E.; Khokhlova, V. L.
1984SvAL...10..187P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Estimate of stellar surface magnetic fields by the
curve-of-growth method.
Authors: Ryabchikova, T. A.; Piskunov, N. E.
1984mast.conf...27R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The study of magnetic field geometry of Ap stars by spectral
line polarization profiles.
Authors: Piskunov, N. E.; Khokhlova, V. L.
1984mast.conf...20P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Numerical modeling of circular-polarization profiles for
magnetic AP stars
Authors: Piskunov, N. E.; Khokhlova, V. L.
1983PAZh....9..665P Altcode:
A numerical model is developed to relate an Ap star's circular
polarization profile to its geometrical parameters at a given phase. The
profiles are integrated over the visible surface of the star as Doppler
shifted by the rotation of the star to obtain an approximation of the
magnetic field structure. When the profiles of a specific spectral
line are calculated according to a centered dipole model, the Ap star's
rotation and nonuniformity of surface element abundances are found to
have a significant effect on the observed field strength. Therefore,
intensity profiles must be used with polarization profiles to define
the star geometry and magnetic field intensity.

---------------------------------------------------------
Title: Numerical Modeling of Circular Polarization Profiles for
Magnetic Ap-Stars
Authors: Piskunov, N. E.; Khokhlova, V. L.
1983SvAL....9..346P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Spectrogram Reducing System Based on the Microdensitometer
MDM-6 Joyce Loebl Coupled with the Minicomputer NOVA3/12
Authors: Piskunov, N. E.; Ptitsyn, D. A.; Ryabchikova, T. A.; Khoklova,
V. L.
1983NInfo..54...45P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Mapping of iron and chromium on the surface of the AP star
Epsilon Ursae Majoris
Authors: Wehlau, W.; Rice, J.; Piskunov, N. E.; Khokhlova, V. L.
1982SvAL....8...15W Altcode: 1982PAZh....8...30W
Epsilon Ursae Majoris (HD 112185) is one of the brightest peculiar A
stars, and it has long been classified as Ap. In connection with an
investigation of the surface of Epsilon UMa, high-precision profiles of
the Fe I, Fe II, Cr I, Cr II lines in the stellar spectrum have been
obtained with the aid of a reticon on a 1.2-m telescope. The obtained
profiles have been employed to solve the inverse problem numerically
by means of a method described by Goncharskii et al. (1977). The line
profiles were recorded between March and August 1980 at 2.4-A dispersion
with the coude spectrograph of a 1.2-A reflector. The profiles were
recorded to better than 1 percent photometric accuracy.

---------------------------------------------------------
Title: The procedure system for files management in OS ES
Authors: Piskunov, N. E.
1982NInfo..51..111P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The procedure system for files menagement in OS ES
Authors: Piskunov, N. E.
1982NInfo..31..111P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The distribution of iron and chromium over the surface of
Epsilon UMa
Authors: Rice, J.; Wehlau, W.; Khokhlova, V. L.; Piskunov, N. E.
1981LIACo..23..265R Altcode: 1981cpsu.conf..265R
The distribution of Fe and Cr on the surface of Epsilon UMa has been
determined using high precision profiles of FeI, FeII, CrI and CrII
lines obtained with a Reticon. The mathematical methods previously
described by Goncharski et al. (1977, 1981) have been used to derive
maps of local equivalent width from the observational data. Both
elements are concentrated in two large regions situated near the
rotational equator. There is an indication that the spots for the
neutral states are displaced in longitude from the spots for the singly
ionized states.