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Author name code: leroy
ADS astronomy entries on 2022-09-14
=author:"Leroy, B."
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Title: VizieR Online Data Catalog: MiMeS survey of magnetism in
massive stars (Wade+, 2016)
Authors: Wade, G. A.; Neiner, C.; Alecian, E.; Grunhut, J. H.; Petit,
V.; de Batz, B.; Bohlender, D. A.; Cohen, D. H.; Henrichs, H. F.;
Kochukhov, O.; Landstreet, J. D.; Manset, N.; Martins, F.; Mathis, S.;
Oksala, M. E.; Owocki, S. P.; Rivinius, T.; Shultz, M. E.; Sundqvist,
J. O.; Townsend, R. H. D.; Ud-Doula, A.; Bouret, J. -C.; Braithwaite,
J.; Briquet, M.; Carciofi, A. C.; David-Uraz, A.; Folsom, C. P.;
Fullerton, A. W.; Leroy, B.; Marcolino, W. L. F.; Moffat, A. F. J.;
Naze, Y.; St, Louis N.; Auriere, M.; Bagnulo, S.; Bailey, J. D.;
Barba, R. H.; Blazere, A.; Bohm, T.; Catala, C.; Donati, J. -F.;
Ferrario, L.; Harrington, D.; Howarth, I. D.; Ignace, R.; Kaper, L.;
Luftinger, T.; Prinja, R.; Vink, J. S.; Weiss, W. W.; Yakunin, I.
2016yCat..74560002W Altcode:
To initiate the observational component of the MiMeS project,
the collaboration was awarded a 640 hour Large Program (LP) with
ESPaDOnS. This award was followed by LP allocations with Narval
(137 nights, or 1213 hours), and with HARPSpol (30 nights , or 280
hours). <P />The TC sample (summarized in Table 4) consists of stars
that were established or suspected to be magnetic at the beginning
of the project. The majority of these stars are confirmed period ic
variables with periods ranging from approximately 1 d to 1.5 years,
with the majority having a period of less than 10 days so that they
are suitable candidates for observational monitoring and mapping. <P
/>(1 data file).
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Title: The magnetic field of the double-lined spectroscopic binary
system HD 5550
Authors: Alecian, E.; Tkachenko, A.; Neiner, C.; Folsom, C. P.;
Leroy, B.
2016A&A...589A..47A Altcode: 2016arXiv160107762A
Context. The origin of fossil fields in intermediate- and high-mass
stars is poorly understood, as is the interplay between binarity and
magnetism during stellar evolution. Thus we have begun a study of
the magnetic properties of a sample of intermediate-mass and massive
short-period binary systems as a function of binarity properties. <BR
/> Aims: This paper specifically aims to characterise the magnetic
field of HD 5550, a double-lined spectroscopic binary system of
intermediate mass. <BR /> Methods: We gathered 25 high-resolution
spectropolarimetric observations of HD 5550 using the instrument
Narval. We first fitted the intensity spectra using Zeeman/ATLAS9
LTE synthetic spectra to estimate the effective temperatures,
microturbulent velocities, and the abundances of some elements of
both components, as well as the light ratio of the system. We then
applied the multi-line least-square deconvolution (LSD) technique to
the intensity and circularly polarised spectra, which provided us with
mean LSD I and V line profiles. We fitted the Stokes I line profiles
to determine the radial and projected rotational velocities of both
stars. We then analysed the shape and evolution of the V profiles using
the oblique rotator model to characterise the magnetic fields of both
stars. <BR /> Results: We confirm the Ap nature of the primary, which
has previously been reported, and find that the secondary displays
spectral characteristics typical of an Am star. While a magnetic field
is clearly detected in the lines of the primary, no magnetic field
is detected in the secondary in any of our observations. If a dipolar
field were present at the surface of the Am star, its polar strength
must be below 40 G. The faint variability observed in the Stokes V
profiles of the Ap star allowed us to propose a rotation period of
6.84<SUB>-0.39</SUB><SUP>+0.61</SUP> d, which is close to the orbital
period (~6.82 d), suggesting that the star is synchronised with its
orbit. By fitting the variability of the V profiles, we propose that
the Ap component hosts a dipolar field inclined with the rotation
axis at an angle β = 156 ± 17 ° and a polar strength B<SUB>d</SUB>
= 65 ± 20 G. The field strength is the weakest known for an Ap
star. <P />Based on the BinaMIcS Large Programme (PI: C. Neiner,
runID: L131N02) obtained at the Telescope Bernard Lyot (USR5026)
operated by the Observatoire Midi-Pyrénées, Université de Toulouse
(Paul Sabatier), Centre National de la Recherche Scientifique of France.
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Title: Weak magnetic field, solid-envelope rotation, and wave-induced
N-enrichment in the SPB star ζ Cassiopeiae
Authors: Briquet, M.; Neiner, C.; Petit, P.; Leroy, B.; de Batz, B.
2016A&A...587A.126B Altcode: 2016arXiv160104517B
<BR /> Aims: The main-sequence B-type star ζ Cassiopeiae is known
as a N-rich star with a magnetic field discovered with the Musicos
spectropolarimeter. We model the magnetic field of the star by means
of 82 new spectropolarimetric observations of higher precision to
investigate the field strength, topology, and effect. <BR /> Methods: We
gathered data with the Narval spectropolarimeter installed at Télescope
Bernard Lyot (TBL; Pic du Midi, France) and applied the least-squares
deconvolution technique to measure the circular polarisation of the
light emitted from ζ Cas. We used a dipole oblique rotator model to
determine the field configuration by fitting the longitudinal field
measurements and by synthesizing the measured Stokes V profiles. We
also made use of the Zeeman-Doppler imaging technique to map the stellar
surface and to deduce the difference in rotation rate between the pole
and equator. <BR /> Results: ζ Cas exhibits a polar field strength
B<SUB>pol</SUB> of 100-150 G, which is the weakest polar field observed
so far in a massive main-sequence star. Surface differential rotation is
ruled out by our observations and the field of ζ Cas is strong enough
to enforce rigid internal rotation in the radiative zone according to
theory. Thus, the star rotates as a solid body in the envelope. <BR />
Conclusions: We therefore exclude rotationally induced mixing as the
cause of the surface N-enrichment. We discuss that the transport of
chemicals from the core to the surface by internal gravity waves is
the most plausible explanation for the nitrogen overabundance at the
surface of ζ Cas. <P />Based on observations obtained at the Télescope
Bernard Lyot (USR5026) operated by the Observatoire Midi-Pyrénées,
Université de Toulouse (Paul Sabatier), Centre National de la Recherche
Scientifique (CNRS) of France.
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Title: The MiMeS survey of magnetism in massive stars: introduction
and overview
Authors: Wade, G. A.; Neiner, C.; Alecian, E.; Grunhut, J. H.; Petit,
V.; Batz, B. de; Bohlender, D. A.; Cohen, D. H.; Henrichs, H. F.;
Kochukhov, O.; Landstreet, J. D.; Manset, N.; Martins, F.; Mathis, S.;
Oksala, M. E.; Owocki, S. P.; Rivinius, Th.; Shultz, M. E.; Sundqvist,
J. O.; Townsend, R. H. D.; ud-Doula, A.; Bouret, J. -C.; Braithwaite,
J.; Briquet, M.; Carciofi, A. C.; David-Uraz, A.; Folsom, C. P.;
Fullerton, A. W.; Leroy, B.; Marcolino, W. L. F.; Moffat, A. F. J.;
Nazé, Y.; Louis, N. St; Aurière, M.; Bagnulo, S.; Bailey, J. D.;
Barbá, R. H.; Blazère, A.; Böhm, T.; Catala, C.; Donati, J. -F.;
Ferrario, L.; Harrington, D.; Howarth, I. D.; Ignace, R.; Kaper, L.;
Lüftinger, T.; Prinja, R.; Vink, J. S.; Weiss, W. W.; Yakunin, I.
2016MNRAS.456....2W Altcode: 2015arXiv151108425W
The MiMeS (Magnetism in Massive Stars) project is a large-scale,
high-resolution, sensitive spectropolarimetric investigation of the
magnetic properties of O- and early B-type stars. Initiated in 2008 and
completed in 2013, the project was supported by three Large Program
allocations, as well as various programmes initiated by independent
principal investigators, and archival resources. Ultimately, over 4800
circularly polarized spectra of 560 O and B stars were collected with
the instruments ESPaDOnS (Echelle SpectroPolarimetric Device for the
Observation of Stars) at the Canada-France-Hawaii Telescope, Narval
at the Télescope Bernard Lyot and HARPSpol at the European Southern
Observatory La Silla 3.6 m telescope, making MiMeS by far the largest
systematic investigation of massive star magnetism ever undertaken. In
this paper, the first in a series reporting the general results of the
survey, we introduce the scientific motivation and goals, describe
the sample of targets, review the instrumentation and observational
techniques used, explain the exposure time calculation designed to
provide sensitivity to surface dipole fields above approximately 100
G, discuss the polarimetric performance, stability and uncertainty
of the instrumentation, and summarize the previous and forthcoming
publications.
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Title: Search for magnetic fields in particle-accelerating
colliding-wind binaries
Authors: Neiner, C.; Grunhut, J.; Leroy, B.; De Becker, M.; Rauw, G.
2015A&A...575A..66N Altcode: 2014arXiv1412.5327N
Context. Some colliding-wind massive binaries, called
particle-accelerating colliding-wind binaries (PACWB), exhibit
synchrotron radio emission, which is assumed to be generated by a
stellar magnetic field. However, no measurement of magnetic fields in
these stars has ever been performed. <BR /> Aims: We aim at quantifying
the possible stellar magnetic fields present in PACWB to provide
constraints for models. <BR /> Methods: We gathered 21 high-resolution
spectropolarimetric observations of 9 PACWB available in the ESPaDOnS,
Narval and HarpsPol archives. We analysed these observations with the
least squares deconvolution method. We separated the binary spectral
components when possible. <BR /> Results: No magnetic signature is
detected in any of the 9 PACWB stars and all longitudinal field
measurements are compatible with 0 G. We derived the upper field
strength of a possible field that could have remained hidden in
the noise of the data. While the data are not very constraining
for some stars, for several stars we could derive an upper limit of
the polar field strength of the order of 200 G. <BR /> Conclusions:
We can therefore exclude the presence of strong or moderate stellar
magnetic fields in PACWB, typical of the ones present in magnetic
massive stars. Weak magnetic fields could however be present in these
objects. These observational results provide the first quantitative
constraints for future models of PACWB. <P />Based on archival
observations obtained at the Télescope Bernard Lyot (USR5026)
operated by the Observatoire Midi-Pyrénées, Université de Toulouse
(Paul Sabatier), Centre National de la Recherche Scientifique (CNRS)
of France, at the Canada-France-Hawaii Telescope (CFHT) operated by
the National Research Council of Canada, the Institut National des
Sciences de l'Univers of the CNRS of France, and the University of
Hawaii, and at the European Southern Observatory (ESO), Chile.
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Title: γ Pegasi: testing Vega-like magnetic fields in B stars
Authors: Neiner, C.; Monin, D.; Leroy, B.; Mathis, S.; Bohlender, D.
2014A&A...562A..59N Altcode: 2013arXiv1312.3521N
Context. The bright B pulsator γ Peg shows both p and g modes of β
Cep and SPB types. It has also been claimed that it is a magnetic star,
while others do not detect any magnetic field. <BR /> Aims: We check
for the presence of a magnetic field, with the aim to characterise it if
it exists, or else provide a firm upper limit of its strength if it is
not detected. If γ Peg is magnetic as claimed, it would make an ideal
asteroseismic target for testing various theoretical scenarios. If
it is very weakly magnetic, it would be the first observation of
an extension of Vega-like fields to early B stars. Finally, if it
is not magnetic and we can provide a very low upper limit on its
non-detected field, it would make an important result for stellar
evolution models. <BR /> Methods: We acquired high resolution, high
signal-to-noise spectropolarimetric Narval data at Telescope Bernard
Lyot (TBL). We also gathered existing dimaPol spectropolarimetric
data from the Dominion Astrophysical Observatory (DAO) and Musicos
spectropolarimetric data from TBL. We analysed the Narval and Musicos
observations using the least-squares deconvolution (LSD) technique
to derive the longitudinal magnetic field and Zeeman signatures in
lines. The longitudinal field strength was also extracted from the Hβ
line observed with the DAO. With a Monte Carlo simulation we derived the
maximum strength of the field possibly hosted by γ Peg. <BR /> Results:
We find that no magnetic signatures are visible in the very high quality
spectropolarimetric data. The average longitudinal field measured in
the Narval data is B<SUB>l</SUB> = -0.1 ± 0.4 G. We derive a very
strict upper limit of the dipolar field strength of B<SUB>pol</SUB> ~
40 G. <BR /> Conclusions: We conclude that γ Peg is not magnetic: it
hosts neither a strong stable fossil field as observed in a fraction
of massive stars nor a very weak Vega-like field. There is therefore
no evidence that Vega-like fields exist in B stars, contrary to the
predictions by fossil field dichotomy scenarios. These scenarios should
thus be revised. Our results also provide strong constraints for stellar
evolution models. <P />Based on observations obtained at the Telescope
Bernard Lyot (USR5026) operated by the Observatoire Midi-Pyrénées,
Université de Toulouse (Paul Sabatier), Centre National de la
Recherche Scientifique of France, and at the Dominion Astrophysical
Observatory.Tables 1-3 are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201323093/olm">http://www.aanda.org</A>
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Title: Discovery of a magnetic field in the CoRoT hybrid B-type
pulsator HD 43317
Authors: Briquet, M.; Neiner, C.; Leroy, B.; Pápics, P. I.; MiMeS
Collaboration
2013A&A...557L..16B Altcode: 2013arXiv1308.4636B
Context. A promising way of testing the impact of a magnetic field on
internal mixing (core overshooting, internal rotation) in main-sequence
B-type stars is to perform asteroseismic studies of a sample of magnetic
pulsators. <BR /> Aims: The CoRoT satellite revealed that the B3IV
star HD 43317 is a hybrid SPB/β Cep-type pulsator that has a wealth of
pulsational constraints on which one can perform a seismic modelling,
in particular, probing the extent of its convective core and mixing
processes. Moreover, indirect indicators of a magnetic field in the star
were observed: rotational modulation due to chemical or temperature
spots and X-ray emission. Our goal was to directly investigate the
field in HD 43317 and, if it is magnetic, to characterise it. <BR
/> Methods: We collected data with the Narval spectropolarimeter
installed at Télescope Bernard Lyot (TBL, Pic du Midi, France)
and applied the least-squares deconvolution technique to measure the
circular polarisation of the light emitted from HD 43317. We modelled
the longitudinal field measurements directly with a dipole. <BR />
Results: Zeeman signatures in the Stokes V profiles of HD 43317 are
clearly detected and rotationally modulated, which proves that this star
exhibits an oblique magnetic field. The modulation with the rotation
period deduced from the CoRoT light curve is also confirmed, and we
found a field strength at the poles of about 1 kG. Our result must be
taken into account in future seismic modelling work of this star. <P
/>Based on observations obtained using the Narval spectropolarimeter
at the Observatoire du Pic du Midi (France), which is operated by the
Institut National des Sciences de l'Univers (INSU).
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Title: Stochastic gravito-inertial modes discovered by CoRoT in the
hot Be star HD 51452
Authors: Neiner, C.; Floquet, M.; Samadi, R.; Espinosa Lara, F.;
Frémat, Y.; Mathis, S.; Leroy, B.; de Batz, B.; Rainer, M.; Poretti,
E.; Mathias, P.; Guarro Fló, J.; Buil, C.; Ribeiro, J.; Alecian,
E.; Andrade, L.; Briquet, M.; Diago, P. D.; Emilio, M.; Fabregat,
J.; Gutiérrez-Soto, J.; Hubert, A. -M.; Janot-Pacheco, E.; Martayan,
C.; Semaan, T.; Suso, J.; Zorec, J.
2012A&A...546A..47N Altcode:
Context. Be stars are rapidly rotating stars with a circumstellar
decretion disk. They usually undergo pressure and/or gravity pulsation
modes excited by the κ-mechanism, i.e. an effect of the opacity of
iron-peak elements in the envelope of the star. In the Milky Way,
p-modes are observed in stars that are hotter than or equal to the
B3 spectral type, while g-modes are observed at the B2 spectral
type and cooler. <BR /> Aims: We observed a B0IVe star, HD 51452,
with the high-precision, high-cadence photometric CoRoT satellite
and high-resolution, ground-based HARPS and SOPHIE spectrographs to
study its pulsations in great detail. We also used the lower resolution
spectra available in the BeSS database. <BR /> Methods: We analyzed the
CoRoT and spectroscopic data with several methods: Clean-NG, FreqFind,
and a sliding window method. We also analyzed spectral quantities,
such as the violet over red (V/R) emission variations, to obtain
information about the variation in the circumstellar environment. We
calculated a stellar structure model with the ESTER code to test
the various interpretation of the results. <BR /> Results: We detect
189 frequencies of variations in the CoRoT light curve in the range
between 0 and 4.5 c d<SUP>-1</SUP>. The main frequencies are also
recovered in the spectroscopic data. In particular we find that HD
51452 undergoes gravito-inertial modes that are not in the domain of
those excited by the κ-mechanism. We propose that these are stochastic
modes excited in the convective zones and that at least some of them
are a multiplet of r-modes (i.e. subinertial modes mainly driven by
the Coriolis acceleration). Stochastically excited gravito-inertial
modes had never been observed in any star, and theory predicted that
their very low amplitudes would be undetectable even with CoRoT. We
suggest that the amplitudes are enhanced in HD 51452 because of the
very rapid stellar rotation. In addition, we find that the amplitude
variations of these modes are related to the occurrence of minor
outbursts. <BR /> Conclusions: Thanks to CoRoT data, we have detected
a new kind of pulsations in HD 51452, which are stochastically excited
gravito-inertial modes, probably due to its very rapid rotation. These
modes are probably also present in other rapidly rotating hot Be
stars. <P />The CoRoT space mission, launched on December 27, 2006,
has been developed and is operated by CNES, with the contribution of
Austria, Belgium, Brazil, ESA (RSSD, and Science Programs), Germany,
and Spain. This work uses observations partly made with the HARPS
instrument at the 3.6-m ESO telescope (La Silla, Chile) in the framework
of the LP182.D-0356, as well as data obtained with Sophie at OHP and
from the BeSS database.Table 3 is available in electronic form at <A
href="http://www.aanda.org">http://www.aanda.org</A>
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Title: Fast calculation of the Lomb-Scargle periodogram using
nonequispaced fast Fourier transforms
Authors: Leroy, B.
2012A&A...545A..50L Altcode:
We present a code for the fast computation of the Lomb-Scargle
periodogram that uses nonequispaced fast Fourier transforms (FFTs). The
computation time has the classical O(Nlog N) behaviour of FFTs,
but is shorter by about one order of magnitude than the "classical"
fast algorithm by Press and Rybicki, and is about five times shorter
that the best GPU-based implementations of the usual O(N<SUP>2</SUP>)
algorithm. This performance is achieved without sacrificing accuracy,
as revealed by comparing the computations done with our FFT-based
algorithm and a naïve one.
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Title: The Kepler characterization of the variability among A-
and F-type stars. I. General overview
Authors: Uytterhoeven, K.; Moya, A.; Grigahcène, A.; Guzik,
J. A.; Gutiérrez-Soto, J.; Smalley, B.; Handler, G.; Balona,
L. A.; Niemczura, E.; Fox Machado, L.; Benatti, S.; Chapellier, E.;
Tkachenko, A.; Szabó, R.; Suárez, J. C.; Ripepi, V.; Pascual, J.;
Mathias, P.; Martín-Ruíz, S.; Lehmann, H.; Jackiewicz, J.; Hekker,
S.; Gruberbauer, M.; García, R. A.; Dumusque, X.; Díaz-Fraile, D.;
Bradley, P.; Antoci, V.; Roth, M.; Leroy, B.; Murphy, S. J.; De Cat,
P.; Cuypers, J.; Kjeldsen, H.; Christensen-Dalsgaard, J.; Breger, M.;
Pigulski, A.; Kiss, L. L.; Still, M.; Thompson, S. E.; van Cleve, J.
2011A&A...534A.125U Altcode: 2011arXiv1107.0335U
Context. The Kepler spacecraft is providing time series of photometric
data with micromagnitude precision for hundreds of A-F type stars. <BR
/> Aims: We present a first general characterization of the pulsational
behaviour of A-F type stars as observed in the Kepler light curves
of a sample of 750 candidate A-F type stars, and observationally
investigate the relation between γ Doradus (γ Dor), δ Scuti
(δ Sct), and hybrid stars. <BR /> Methods: We compile a database
of physical parameters for the sample stars from the literature and
new ground-based observations. We analyse the Kepler light curve of
each star and extract the pulsational frequencies using different
frequency analysis methods. We construct two new observables, "energy"
and "efficiency", related to the driving energy of the pulsation
mode and the convective efficiency of the outer convective zone,
respectively. <BR /> Results: We propose three main groups to describe
the observed variety in pulsating A-F type stars: γ Dor, δ Sct, and
hybrid stars. We assign 63% of our sample to one of the three groups,
and identify the remaining part as rotationally modulated/active stars,
binaries, stars of different spectral type, or stars that show no clear
periodic variability. 23% of the stars (171 stars) are hybrid stars,
which is a much higher fraction than what has been observed before. We
characterize for the first time a large number of A-F type stars (475
stars) in terms of number of detected frequencies, frequency range,
and typical pulsation amplitudes. The majority of hybrid stars show
frequencies with all kinds of periodicities within the γ Dor and δ
Sct range, also between 5 and 10 d<SUP>-1</SUP>, which is a challenge
for the current models. We find indications for the existence of δ
Sct and γ Dor stars beyond the edges of the current observational
instability strips. The hybrid stars occupy the entire region within
the δ Sct and γ Dor instability strips and beyond. Non-variable
stars seem to exist within the instability strips. The location of
γ Dor and δ Sct classes in the (T<SUB>eff</SUB>, log g)-diagram
has been extended. We investigate two newly constructed variables,
"efficiency" and "energy", as a means to explore the relation between
γ Dor and δ Sct stars. <BR /> Conclusions: Our results suggest a
revision of the current observational instability strips of δ Sct and
γ Dor stars and imply an investigation of pulsation mechanisms to
supplement the κ mechanism and convective blocking effect to drive
hybrid pulsations. Accurate physical parameters for all stars are
needed to confirm these findings.
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Title: VizieR Online Data Catalog: Variability of A- and F-stars
from Kepler (Uytterhoeven+ 2011)
Authors: Uytterhoeven, K.; Moya, A.; Grigahcene, A.; Guzik, J. A.;
Gutierrez-Soto, J.; Smalley, B.; Handler, G.; Balona, L. A.; Niemczura,
E.; Fox Machado, L.; Benatti, S.; Chapellier, E.; Tkachenko, A.; Szabo,
R.; Suarez, J. C.; Ripepi, V.; Pascual, J.; Mathias, P.; Martin-Ruiz,
S.; Lehmann, H.; Jackiewicz, J.; Hekker, S.; Gruberbauer, M.; Garcia,
R. A.; Dumusque, X.; Diaz-Fraile, D.; Bradley, P.; Antoci, V.; Roth,
M.; Leroy, B.; Murphy, S. J.; De Cat, P.; Cuypers, J.; Kjeldsen, H.;
Christensen-Dalsgaard, J.; Breger, M.; Pigulski, A.; Kiss, L. L.;
Still, M.; Thompson, S. E.; van Cleve, J.
2011yCat..35340125U Altcode: 2011yCat..35349125U
We compile a database of physical parameters for the sample stars from
the literature and new ground-based observations. We analyse the Kepler
light curve of each star and extract the pulsational frequencies using
different frequency analysis methods. We construct two new observables,
'energy' and 'efficiency', related to the driving energy of the
pulsation mode and the convective efficiency of the outer convective
zone, respectively. <P />(5 data files).
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Title: Kepler observations of the variability in B-type stars
Authors: Balona, L. A.; Pigulski, A.; De Cat, P.; Handler, G.;
Gutiérrez-Soto, J.; Engelbrecht, C. A.; Frescura, F.; Briquet, M.;
Cuypers, J.; Daszyńska-Daszkiewicz, J.; Degroote, P.; Dukes, R. J.;
Garcia, R. A.; Green, E. M.; Heber, U.; Kawaler, S. D.; Lehmann,
H.; Leroy, B.; Molenda-Żaaowicz, J.; Neiner, C.; Noels, A.; Nuspl,
J.; Østensen, R.; Pricopi, D.; Roxburgh, I.; Salmon, S.; Smith,
M. A.; Suárez, J. C.; Suran, M.; Szabó, R.; Uytterhoeven, K.;
Christensen-Dalsgaard, J.; Kjeldsen, H.; Caldwell, D. A.; Girouard,
F. R.; Sanderfer, D. T.
2011MNRAS.413.2403B Altcode: 2011MNRAS.tmp..298B; 2011arXiv1103.0644B
The analysis of the light curves of 48 B-type stars observed by Kepler
is presented. Among these are 15 pulsating stars, all of which show low
frequencies, characteristic of slowly pulsating B (SPB) stars. Seven of
these stars also show a few weak, isolated high frequencies and they
could be considered as SPB/β Cephei (β Cep) hybrids. In all cases,
the frequency spectra are quite different from what is seen from
ground-based observations. We suggest that this is because most of
the low frequencies are modes of high degree which are predicted to be
unstable in models of mid-B stars. We find that there are non-pulsating
stars within the β Cep and SPB instability strips. Apart from the
pulsating stars, we can identify stars with frequency groupings similar
to what is seen in Be stars but which are not Be stars. The origin of
the groupings is not clear, but may be related to rotation. We find
periodic variations in other stars which we attribute to proximity
effects in binary systems or possibly rotational modulation. We find
no evidence for pulsating stars between the cool edge of the SPB
and the hot edge of the δ Sct instability strips. None of the stars
shows the broad features which can be attributed to stochastically
excited modes as recently proposed. Among our sample of B stars are
two chemically peculiar stars, one of which is a HgMn star showing
rotational modulation in the light curve.
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Title: Asteroseismology of solar-type stars with Kepler I: Data
analysis
Authors: Karoff, C.; Chaplin, W. J.; Appourchaux, T.; Elsworth, Y.;
Garcia, R. A.; Houdek, G.; Metcalfe, T. S.; Molenda-Żakowicz, J.;
Monteiro, M. J. P. F. G.; Thompson, M. J.; Christensen-Dalsgaard, J.;
Gilliland, R. L.; Kjeldsen, H.; Basu, S.; Bedding, T. R.; Campante,
T. L.; Eggenberger, P.; Fletcher, S. T.; Gaulme, P.; Handberg, R.;
Hekker, S.; Martic, M.; Mathur, S.; Mosser, B.; Regulo, C.; Roxburgh,
I. W.; Salabert, D.; Stello, D.; Verner, G. A.; Belkacem, K.; Biazzo,
K.; Cunha, M. S.; Gruberbauer, M.; Guzik, J. A.; Kupka, F.; Leroy,
B.; Ludwig, H. -G.; Mathis, S.; Noels, A.; Noyes, R. W.; Roca Cortes,
T.; Roth, M.; Sato, K. H.; Schmitt, J.; Suran, M. D.; Trampedach,
R.; Uytterhoeven, K.; Ventura, R.
2010AN....331..972K Altcode: 2010arXiv1005.0507K
We report on the first asteroseismic analysis of solar-type stars
observed by Kepler. Observations of three G-type stars, made at
one-minute cadence during the first 33.5 days of science operations,
reveal high signal-to-noise solar-like oscillation spectra in all three
stars: About 20 modes of oscillation can clearly be distinguished
in each star. We discuss the appearance of the oscillation spectra,
including the presence of a possible signature of faculae, and the
presence of mixed modes in one of the three stars.
---------------------------------------------------------
Title: Photometric variability of the Be star CoRoT-ID 102761769
Authors: Emilio, M.; Andrade, L.; Janot-Pacheco, E.; Baglin, A.;
Gutiérrez-Soto, J.; Suárez, J. C.; de Batz, B.; Diago, P.; Fabregat,
J.; Floquet, M.; Frémat, Y.; Huat, A. L.; Hubert, A. M.; Espinosa
Lara, F.; Leroy, B.; Martayan, C.; Neiner, C.; Semaan, T.; Suso, J.
2010A&A...522A..43E Altcode: 2010arXiv1010.5576E
Context. Classical Be stars are rapid rotators of spectral type
late O to early A and luminosity class V-III, which exhibit Balmer
emission lines and often a near infrared excess originating in an
equatorially concentrated circumstellar envelope, both produced by
sporadic mass ejection episodes. The causes of the abnormal mass
loss (the so-called Be phenomenon) are as yet unknown. <BR /> Aims:
For the first time, we can now study in detail Be stars outside the
Earth's atmosphere with sufficient temporal resolution. We investigate
the variability of the Be Star CoRoT-ID 102761769 observed with the
CoRoT satellite in the exoplanet field during the initial run. <BR />
Methods: One low-resolution spectrum of the star was obtained with
the INT telescope at the Observatorio del Roque de los Muchachos. A
time series analysis was performed using both cleanest and singular
spectrum analysis algorithms to the CoRoT light curve. To identify
the pulsation modes of the observed frequencies, we computed a
set of models representative of CoRoT-ID 102761769 by varying its
main physical parameters inside the uncertainties discussed. <BR />
Results: We found two close frequencies related to the star. They
are 2.465 c d<SUP>-1</SUP> (28.5 μHz) and 2.441 c d<SUP>-1</SUP>
(28.2 μHz). The precision to which those frequencies were found is
0.018 c d<SUP>-1</SUP> (0.2 μHz). The projected stellar rotation was
estimated to be 120 km s<SUP>-1</SUP> from the Fourier transform of
spectral lines. If CoRoT-ID 102761769 is a typical Galactic Be star it
rotates near the critical velocity. The critical rotation frequency
of a typical B5-6 star is about 3.5 c d<SUP>-1</SUP> (40.5 μHz),
which implies that the above frequencies are really caused by stellar
pulsations rather than star's rotation. <P />The CoRoT space mission
was developed and is operated by the French space agency CNES, with
participation of ESA's RSSD and Science Programmes, Austria, Belgium,
Brazil, Germany, and Spain.
---------------------------------------------------------
Title: The Asteroseismic Potential of Kepler: First Results for
Solar-Type Stars
Authors: Chaplin, W. J.; Appourchaux, T.; Elsworth, Y.; García,
R. A.; Houdek, G.; Karoff, C.; Metcalfe, T. S.; Molenda-Żakowicz,
J.; Monteiro, M. J. P. F. G.; Thompson, M. J.; Brown, T. M.;
Christensen-Dalsgaard, J.; Gilliland, R. L.; Kjeldsen, H.; Borucki,
W. J.; Koch, D.; Jenkins, J. M.; Ballot, J.; Basu, S.; Bazot, M.;
Bedding, T. R.; Benomar, O.; Bonanno, A.; Brandão, I. M.; Bruntt,
H.; Campante, T. L.; Creevey, O. L.; Di Mauro, M. P.; Doǧan,
G.; Dreizler, S.; Eggenberger, P.; Esch, L.; Fletcher, S. T.;
Frandsen, S.; Gai, N.; Gaulme, P.; Handberg, R.; Hekker, S.; Howe,
R.; Huber, D.; Korzennik, S. G.; Lebrun, J. C.; Leccia, S.; Martic,
M.; Mathur, S.; Mosser, B.; New, R.; Quirion, P. -O.; Régulo, C.;
Roxburgh, I. W.; Salabert, D.; Schou, J.; Sousa, S. G.; Stello, D.;
Verner, G. A.; Arentoft, T.; Barban, C.; Belkacem, K.; Benatti, S.;
Biazzo, K.; Boumier, P.; Bradley, P. A.; Broomhall, A. -M.; Buzasi,
D. L.; Claudi, R. U.; Cunha, M. S.; D'Antona, F.; Deheuvels, S.;
Derekas, A.; García Hernández, A.; Giampapa, M. S.; Goupil, M. J.;
Gruberbauer, M.; Guzik, J. A.; Hale, S. J.; Ireland, M. J.; Kiss,
L. L.; Kitiashvili, I. N.; Kolenberg, K.; Korhonen, H.; Kosovichev,
A. G.; Kupka, F.; Lebreton, Y.; Leroy, B.; Ludwig, H. -G.; Mathis, S.;
Michel, E.; Miglio, A.; Montalbán, J.; Moya, A.; Noels, A.; Noyes,
R. W.; Pallé, P. L.; Piau, L.; Preston, H. L.; Roca Cortés, T.;
Roth, M.; Sato, K. H.; Schmitt, J.; Serenelli, A. M.; Silva Aguirre,
V.; Stevens, I. R.; Suárez, J. C.; Suran, M. D.; Trampedach, R.;
Turck-Chièze, S.; Uytterhoeven, K.; Ventura, R.; Wilson, P. A.
2010ApJ...713L.169C Altcode: 2010arXiv1001.0506C
We present preliminary asteroseismic results from Kepler on three G-type
stars. The observations, made at one-minute cadence during the first
33.5 days of science operations, reveal high signal-to-noise solar-like
oscillation spectra in all three stars: about 20 modes of oscillation
may be clearly distinguished in each star. We discuss the appearance of
the oscillation spectra, use the frequencies and frequency separations
to provide first results on the radii, masses, and ages of the stars,
and comment in the light of these results on prospects for inference
on other solar-type stars that Kepler will observe.
---------------------------------------------------------
Title: The B0.5 IVe CoRoT target HD 49330. II. Spectroscopic
ground-based observations
Authors: Floquet, M.; Hubert, A. -M.; Huat, A. -L.; Frémat, Y.;
Janot-Pacheco, E.; Gutiérrez-Soto, J.; Neiner, C.; de Batz, B.;
Leroy, B.; Poretti, E.; Amado, P.; Catala, C.; Rainer, M.; Diaz, D.;
Uytterhoeven, K.; Andrade, L.; Diago, P. D.; Emilio, M.; Espinosa Lara,
F.; Fabregat, J.; Martayan, C.; Semaan, T.; Suso, J.
2009A&A...506..103F Altcode:
Context: We present spectroscopic ground-based observations of the early
Be star HD 49330 obtained simultaneously with the CoRoT-LRA1 run just
before the burst observed in the CoRoT data. <BR />Aims: Ground-based
spectroscopic observations of the early Be star HD 49330 obtained
during the precursor phase and just before the start of an outburst
allow us to disantangle stellar and circumstellar contributions and
identify modes of stellar pulsations in this rapidly rotating star. <BR
/>Methods: Time series analysis (TSA) is performed on photospheric line
profiles of He I and Si III by means of the least squares method. <BR
/>Results: We find two main frequencies f1 = 11.86 c d<SUP>-1</SUP>
and f2 = 16.89 c d<SUP>-1</SUP> which can be associated with high order
p-mode pulsations. We also detect a frequency f3 = 1.51 c d<SUP>-1</SUP>
which can be associated with a low order g-mode. Moreover we show that
the stellar line profile variability changed over the spectroscopic
run. These results are in agreement with the results of the CoRoT
data analysis, as shown in Huat et al. (2009). <BR />Conclusions:
Our study of mid- and short-term spectroscopic variability allows the
identification of p- and g-modes in HD 49330. It also allows us to
display changes in the line profile variability before the start of
an outburst. This brings new constraints for the seimic modelling of
this star. <P />Based on observations made with ESO Telescopes at La
Silla Observatory under the ESO Large Programme: LP178.D-0361, and on
data collected with the TBL at Pic du Midi Observatory (France).
---------------------------------------------------------
Title: The B0.5IVe CoRoT target HD 49330. I. Photometric analysis
from CoRoT data
Authors: Huat, A. -L.; Hubert, A. -M.; Baudin, F.; Floquet, M.; Neiner,
C.; Frémat, Y.; Gutiérrez-Soto, J.; Andrade, L.; de Batz, B.; Diago,
P. D.; Emilio, M.; Espinosa Lara, F.; Fabregat, J.; Janot-Pacheco,
E.; Leroy, B.; Martayan, C.; Semaan, T.; Suso, J.; Auvergne, M.;
Catala, C.; Michel, E.; Samadi, R.
2009A&A...506...95H Altcode:
Context: Be stars undergo outbursts producing a circumstellar disk
from the ejected material. The beating of non-radial pulsations has
been put forward as a possible mechanism of ejection. <BR />Aims:
We analyze the pulsational behavior of the early B0.5IVe star HD
49330 observed during the first CoRoT long run towards the Galactical
anticenter (LRA1). This Be star is located close to the lower edge of
the β Cephei instability strip in the HR diagram and showed a 0.03
mag outburst during the CoRoT observations. It is thus an ideal case
for testing the aforementioned hypothesis. <BR />Methods: We analyze
the CoRoT light curve of HD 49330 using Fourier methods and non-linear
least square fitting. <BR />Results: In this star, we find pulsation
modes typical of β Cep stars (p modes) and SPB stars (g modes)
with amplitude variations along the run directly correlated with the
outburst. These results provide new clues about the origin of the Be
phenomenon as well as strong constraints on the seismic modelling of
Be stars. <P />Tables 3 to 7 are only available in electronic form
at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/506/95
---------------------------------------------------------
Title: Low-amplitude variations detected by CoRoT in the B8IIIe
star HD 175869
Authors: Gutiérrez-Soto, J.; Floquet, M.; Samadi, R.; Neiner, C.;
Garrido, R.; Fabregat, J.; Frémat, Y.; Diago, P. D.; Huat, A. -L.;
Leroy, B.; Emilio, M.; Hubert, A. -M.; Andrade, O. Thizy L.; de Batz,
B.; Janot-Pacheco, E.; Espinosa Lara, F.; Martayan, C.; Semaan, T.;
Suso, J.; Auvergne, M.; Chaintreuil, S.; Michel, E.; Catala, C.
2009A&A...506..133G Altcode:
Context: The origin of the short-term variability in Be stars remains
a matter of controversy. Pulsations and rotational modulation are
the components of the favored hypothesis. <BR />Aims: We present our
analysis of CoRoT data of the B8IIIe star HD 175869 observed during
the first short run in the center direction (SRC1). <BR />Methods:
We review both the instrumental effects visible in the CoRoT light
curve and the analysis methods used by the CoRoT Be team. We applied
these methods to the CoRoT light curve of the star HD 175869. A
search for line-profile variations in the spectroscopic data was also
performed. We also searched for a magnetic field, by applying the LSD
technique to spectropolarimetric data. <BR />Results: The light curve
exhibits low-amplitude variations of the order of 300 μmag with a
double wave shape. A frequency within the range determined for the
rotational frequency and 6 of its harmonics are detected. The main
frequency and its first harmonic exhibit amplitude variations of a few
days. Other significant frequencies of low-amplitude from 25 to a few
μmag are also found. The analysis of line profiles from ground-based
spectroscopic data does not detect any variation. In addition, no
Zeeman signature was found. <BR />Conclusions: Inhomogeneities caused
by stellar activity in or just above the photosphere are proposed to
produce the photometric variability detected by CoRoT in the Be star
HD 175869. The hypothesis that non-radial pulsations are the origin
of these variations cannot be excluded.
---------------------------------------------------------
Title: Pulsations in the late-type Be star HD 50 209 detected by CoRoT
Authors: Diago, P. D.; Gutiérrez-Soto, J.; Auvergne, M.; Fabregat, J.;
Hubert, A. -M.; Floquet, M.; Frémat, Y.; Garrido, R.; Andrade, L.; de
Batz, B.; Emilio, M.; Espinosa Lara, F.; Huat, A. -L.; Janot-Pacheco,
E.; Leroy, B.; Martayan, C.; Neiner, C.; Semaan, T.; Suso, J.; Catala,
C.; Poretti, E.; Rainer, M.; Uytterhoeven, K.; Michel, E.; Samadi, R.
2009A&A...506..125D Altcode: 2009arXiv0909.4524D
Context: The presence of pulsations in late-type Be stars is still a
matter of controversy. It constitutes an important issue to establish
the relationship between non-radial pulsations and the mass-loss
mechanism in Be stars. <BR />Aims: To contribute to this discussion,
we analyse the photometric time series of the B8IVe star HD 50 209
observed by the CoRoT mission in the seismology field. <BR />Methods:
We use standard Fourier techniques and linear and non-linear least
squares fitting methods to analyse the CoRoT light curve. In addition,
we applied detailed modelling of high-resolution spectra to obtain
the fundamental physical parameters of the star. <BR />Results: We
have found four frequencies which correspond to gravity modes with
azimuthal order m=0,-1,-2,-3 with the same pulsational frequency in the
co-rotating frame. We also found a rotational period with a frequency
of 0.679 cd<SUP>-1</SUP> (7.754 μHz). <BR />Conclusions: HD 50 209 is
a pulsating Be star as expected from its position in the HR diagram,
close to the SPB instability strip. <P />Based on observations made
with the CoRoT satellite, with FEROS at the 2.2 m telescope of the
La Silla Observatory under the ESO Large Programme LP178.D-0361
and with Narval at the Télescope Bernard Lyot of the Pic du Midi
Observatory. Current address: Valencian International University (VIU),
José Pradas Gallen s/n, 12006 Castellón, Spain. Current address:
Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot; CEA, IRFU,
SAp, centre de Saclay, 91191 Gif-sur-Yvette, France.
---------------------------------------------------------
Title: The pulsations of the B5IVe star HD 181231 observed with
CoRoT and ground-based spectroscopy
Authors: Neiner, C.; Gutiérrez-Soto, J.; Baudin, F.; de Batz, B.;
Frémat, Y.; Huat, A. L.; Floquet, M.; Hubert, A. -M.; Leroy, B.;
Diago, P. D.; Poretti, E.; Carrier, F.; Rainer, M.; Catala, C.; Thizy,
O.; Buil, C.; Ribeiro, J.; Andrade, L.; Emilio, M.; Espinosa Lara,
F.; Fabregat, J.; Janot-Pacheco, E.; Martayan, C.; Semaan, T.; Suso,
J.; Baglin, A.; Michel, E.; Samadi, R.
2009A&A...506..143N Altcode:
Context: <ASTROBJ>H</ASTROBJ>D 181231 is a B5IVe star, which has
been observed with the CoRoT satellite during ~5 consecutive
months and simultaneously from the ground in spectroscopy and
spectropolarimetry. <BR />Aims: By analysing these data, we aim to
detect and characterize as many pulsation frequencies as possible, to
search for the presence of beating effects possibly at the origin of
the Be phenomenon. Our results will also provide a basis for seismic
modelling. <BR />Methods: The fundamental parameters of the star are
determined from spectral fitting and from the study of the circumstellar
emission. The CoRoT photometric data and ground-based spectroscopy are
analysed using several Fourier techniques: Clean-ng, Pasper, and Tisaft,
as well as a time-frequency technique. A search for a magnetic field
is performed by applying the LSD technique to the spectropolarimetric
data. <BR />Results: We find that <ASTROBJ>H</ASTROBJ>D 181231 is
a B5IVe star seen with an inclination of ~45 degrees. No magnetic
field is detected in its photosphere. We detect at least 10 independent
significant frequencies of variations among the 54 detected frequencies,
interpreted in terms of non-radial pulsation modes and rotation. Two
longer-term variations are also detected: one at ~14 days resulting
from a beating effect between the two main frequencies of short-term
variations, the other at ~116 days due either to a beating of
frequencies or to a zonal pulsation mode. <BR />Conclusions: Our
analysis of the CoRoT light curve and ground-based spectroscopic
data of <ASTROBJ>H</ASTROBJ>D 181231 has led to the determination
of the fundamental and pulsational parameters of the star, including
beating effects. This will allow a precise seismic modelling of this
star. <P />Based on observations obtained with the CoRoT satellite,
with FEROS at the 2.2 m télescope of the La Silla Observatory under
the ESO Large Programme LP178.D-0361, with Narval at the Télescope
Bernard Lyot of the Pic du Midi Observatory, and collected from the
BeSS database. Table 5 is only available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/506/143
---------------------------------------------------------
Title: VizieR Online Data Catalog: Pulsations of HD 181231 (Neiner+,
2009)
Authors: Neiner, C.; Gutierrez-Soto, J.; Baudin, F.; de Batz, B.;
Fremat, Y.; Huat, A. -L.; Floquet, M.; Hubert, A. -M.; Leroy, B.;
Diago, P. D.; Poretti, E.; Carrier, F.; Rainer, M.; Catala, C.; Thizy,
O.; Buil, C.; Ribeiro, J.; Andrade, L.; Emilio, M.; Espinosa, F. Lara;
Fabregat, J.; Janot-Pacheco, E.; Martayan, C.; Semaan, T.; Suso, J.;
Baglin, A.; Michel, E.; Samadi, R.
2009yCat..35060143N Altcode:
Frequencies (in c/d and microHz) detected in the CoRoT data of HD181231
with the TiSAFT, Clean-NG, and Pasper methods. The minimum detectable
frequency is 1/T=0.0064 c/d, i.e., 0.075microHz, where T is the length
of the run. The error bar of the frequencies is Delta_f=1/(4T)=0.0016
c/d, i.e., 0.019 microHz. The amplitudes and phases calculated with
Amphi for each of the three sets of frequencies are reported in
Cols. 5 and 6 together with their error bars. The last column gives
our interpretation of each frequency. <P />(1 data file).
---------------------------------------------------------
Title: VizieR Online Data Catalog: Fourier analysis of HD 49330
CoRoT light curve (Huat+, 2009)
Authors: Huat, A. -L.; Hubert, A. -M.; Baudin, F.; Floquet, M.; Neiner,
C.; Fremat, Y.; Gutierrez-Soto, J.; Andrade, L.; de Batz, B.; Diago,
P. D.; Emilio, M.; Espinosa, F. Lara; Fabregat, J.; Janot-Pacheco,
E.; Leroy, B.; Martayan, C.; Semaan, T.; Suso, J.; Auvergne, M.;
Catala, C.; Michel, E.; Samadi, R.
2009yCat..35060095H Altcode:
This work analyses the high precision photometric light curve obtained
for the CoRoT target HD49330 (B0.5 IVe) which was observed during
136.886 days with a sample of 32s. During the CoRoT run the star
underwent an outburst often observed in hot Be star. The CoRoT light
curve was analysed using Fourier methods and non-linear least square
fitting. <P />(5 data files).
---------------------------------------------------------
Title: Low-amplitude variations detected by CoRoT in the late type
Be star HD 175869
Authors: Gutiérrez-Soto, J.; Floquet, M.; Neiner, C.; Hubert, A. -M.;
Frémat, Y.; Andrade, L.; de Batz, B.; Diago, P. D.; Emilio, M.;
Fabregat, J.; Facanha, W.; Huat, A. -L.; Janot-Pacheco, E.; Leroy,
B.; Martayan, C.; Suso, J.; Garrido, R.
2009CoAst.158..208G Altcode:
We present the analysis of the CoRoT data of the B8IIIe star HD
175869 observed during a short run (27.3 days). The light curve shows
low-amplitude variations of the order of 0.3 mmag. A frequency within
the range determined for the rotational frequency and its 5 harmonics
are detected. Other significant frequencies with a low amplitude of a
few ppm are also found. The analysis of line profiles from ground-based
spectroscopic data does not show any variation.
---------------------------------------------------------
Title: Application of the TiSAFT code (Time Series Analysis with
Fisher's Test)
Authors: Huat, A. -L.; Leroy, B.; Diago, P. D.
2009CoAst.158..211H Altcode:
A new code for extracting frequencies, amplitudes and phases in a
time series has been developed for the CoRoT data analysis: TiSAFT
(Time Series Analysis with Fisher's Test of significance). We provide
an application of the TiSAFT code on a simulated β Cephei light curve
and on CoRoT data of a Be star, as well as a comparison with other
codes already used in the CoRoT Be team.
---------------------------------------------------------
Title: Preliminary results on the pulsations of Be stars with CoRoT
Authors: Neiner, C.; Gutiérrez-Soto, J.; Floquet, M.; Huat, A. -L.;
Hubert, A. -M.; de Batz, B.; Leroy, B.; Frémat, Y.; Andrade, L.;
Diago, P. D.; Emilio, M.; Fabregat, J.; Janot-Pacheco, E.; Martayan,
C.; Semaan, T.; Suso, J.
2009CoAst.158..319N Altcode:
We present preliminary results of the study of pulsations of Be stars
from CoRoT observations. CoRoT detected many pulsation frequencies in
all observed Be stars, usually interpreted in terms of g-modes but
sometimes also corresponding to p-modes. Even in late Be stars, for
which the detection of pulsation frequencies is very difficult from the
ground, because of their very low amplitude, the quality and precision
of the CoRoT data allows us to detect many frequencies. Seismic models
have not yet been calculated but the calculations are ongoing.
---------------------------------------------------------
Title: First results on the Be stars observed with the CoRoT satellite
Authors: Gutierrez-Soto, J.; Neiner, C.; Hubert, A. -M.; Floquet,
M.; Huat, A. -L.; Diago, P. D.; Fabregat, J.; Leroy, B.; De Batz, B.;
Andrade, L.; Emilio, M.; Facanha, W.; Fremat, Y.; Janot-Pacheco, E.;
Martayan, C.; Suso, J.
2008CoAst.157...70G Altcode:
In this paper we present an overview of the analysis of some of the
Be stars observed with the CoRoT satellite up to this date. Be stars
are very fast-rotating B-type stars which may pulsate as β Cephei
or SPB stars. CoRoT has already observed 5 bright Be stars in the
seismology fields and several tens of fainter ones in the exoplanet
fields with an unprecedented quality and with a time duration from
20 to 150 days. Multiple frequencies are detected in the majority
of the stars. Pulsations, outbursts, beating phenomenon, possible
transient modes, rotation, amplitude variability, etc. have been found
in their light curves. In order to complement this study, ground-based
spectroscopic data have also been analysed for the stars located in
the seismology fields.
---------------------------------------------------------
Title: The pulsations of the B5IVe star HD181231 revealed by CoRoT
Authors: Neiner, C.; Gutierrez-Soto, J.; Fremat, Y.; Floquet, M.;
Hubert, A. -M.; Leroy, B.; de Batz, B.; Huat, A. -L.; Martayan, C.;
Andrade, L.; Emilio, M.; Fabregat, J.; Facanha, W.; Janot-Pacheco,
E.; Suso, J.
2008CoAst.157..349N Altcode:
We present the first results of the analysis of the light curve of
the B5IVe star HD 181231 obtained during a long run (5 months) of
the CoRoT mission. The light curve shows clear pulsations and even
beating effects. Several frequencies are detected. Ground-based spec-
troscopic data have also been analyzed and help to determine the
rotation frequency and identify pulsation modes.
---------------------------------------------------------
Title: First asteroseismic results from CoRoT
Authors: Michel, E.; Baglin, A.; Weiss, W. W.; Auvergne, M.; Catala,
C.; Aerts, C.; Appourchaux, T.; Barban, C.; Baudin, F.; Briquet, M.;
Carrier, F.; Degroote, P.; De Ridder, J.; Garcia, R. A.; Garrido,
R.; Gutiérrez-Soto, J.; Kallinger, T.; Lefevre, L.; Neiner,
C.; Poretti, E.; Samadi, R.; Sarro, L.; Alecian, G.; Andrade, L.;
Ballot, J.; Benomar, O.; Berthomieu, G.; Boumier, P.; Charpinet, S.;
de Batz, B.; Deheuvels, S.; Dupret, M. -A.; Emilio, M.; Fabregat,
J.; Facanha, W.; Floquet, M.; Frémat, Y.; Fridlund, M.; Goupil,
M. -J.; Grotsch-Noels, A.; Handler, G.; Huat, A. -L.; Hubert, A. -M.;
Janot-Pacheco, E.; Kjeldsen, H.; Lebreton, Y.; Leroy, B.; Martayan,
C.; Mathias, P.; Miglio, A.; Montalban, J.; Monteiro, M. J. P. F. G.;
Mosser, B.; Provost, J; Regulo, C.; Renan de Medeiros, J.; Ribas,
I.; Roca Cortés, T.; Roxburgh, I.; Suso, J.; Thoul, A.; Toutain, T.;
Tiphene, D.; Turck-Chieze, S.; Vauclair, S.; Vauclair, G.; Zwintz, K.
2008CoAst.156...73M Altcode:
About one year after the end of the first observational run and
six months after the first CoRoT data delivery, we comment the data
exploitation progress for different types of stars. We consider first
results to illustrate how these data of unprecedented quality shed a
new light on the field of stellar seismology.
---------------------------------------------------------
Title: First results on Be stars with CoRoT
Authors: Gutiérrez-Soto, J.; Neiner, C.; Hubert, A. -M.; Floquet,
M.; Huat, A. -L.; Diago, P. D.; Fabregat, J.; Leroy, B.; de Batz,
B.; Andrade, L.; Emilio, M.; Facanha, W.; Frémat, Y.; Janot-Pacheco,
E.; Martayan, M.; Suso, J.; Garrido, R.
2008sf2a.conf..475G Altcode:
In this paper we present an overview of the analysis of some of the
Be stars observed with the CoRoT satellite up to this date. Be stars
are very fast-rotating B-type stars which may pulsate as β Cephei
or SPB stars. CoRoT has already observed 5 bright Be stars in the
seismology fields and several tens of fainter ones in the exoplanet
fields with an unprecedented quality and with a time duration from 20
to 150 days. Multiple frequencies are detected in the majority of the
stars. Pulsations, outbursts, beating phenomenon, rotation, amplitude
variability, etc. have been found in their light curves. In order to
complement this study, ground-based spectroscopic data have also been
analysed for the stars located in the seismology fields.
---------------------------------------------------------
Title: The Gaia satellite: a tool for Emission Line Stars and
Hot Stars
Authors: Martayan, C.; Frémat, Y.; Blomme, R.; Jonckheere, A.; Borges,
M.; de Batz, B.; Leroy, B.; Sordo, R.; Bouret, J. -C.; Martins, F.;
Zorec, J.; Neiner, C.; Nazé, Y.; Alecian, E.; Floquet, M.; Hubert,
A. -M.; Briot, D.; Miroshnichenko, A.; Kolka, I.; Stee, P.; Lanz,
T.; Meynet, G.
2008sf2a.conf..499M Altcode: 2008arXiv0809.4417M
The Gaia satellite will be launched at the end of 2011. It will
observe at least 1 billion stars, and among them several million
emission line stars and hot stars. Gaia will provide parallaxes for
each star and spectra for stars till V magnitude equal to 17. After a
general description of Gaia, we present the codes and methods, which
are currently developed by our team. They will provide automatically
the astrophysical parameters and spectral classification for the hot
and emission line stars in the Milky Way and other close local group
galaxies such as the Magellanic Clouds.
---------------------------------------------------------
Title: New Methods for the Simulation of Ablative Thermal Protections
Authors: Nguyen-Bui, N. T. H.; Duffa, G.; Dubroca, B.; Leroy, B.
2006ESASP.631E..13N Altcode: 2006tpsh.confE..13N
No abstract at ADS
---------------------------------------------------------
Title: Inversion of line profiles using principal component analysis:
some practical guidelines
Authors: Leroy, B.
2003EAS.....9..117L Altcode:
Modern spectro-polarimeters produce huge amounts of data, and the <P
/>computing time needed to achieve data inversion is then becoming an
<P />important bottleneck for the modelling activity. Recently, an <P
/>alternative to the traditional non-linear least squares technique <P
/>has been proposed; it relies on an old technique in multivariate <P
/>analysis, principal component analysis (PCA), and proves to be <P
/>much faster than traditional techniques (a gain of two <P />orders
of magnitude in computation time is not unusual). We will <P />briefly
recall this technique and discuss some means of making it <P />still
more robust.
---------------------------------------------------------
Title: Lockheed Martin Team's Next Generation Space Telescope (NGST)
Reference Architecture
Authors: Martin, F.; Lesyna, L.; LeRoy, B.; Menzel, M.; Andersen,
G.; Hyatt, B.; Triebes, K.; Rudiger, C.; Stier, M.; Cox, C.; Delp,
C.; Hachkowski, R.; Hardman, G.; Keane, M.; MacFarlane, M.; Mordino,
A.; Krim, M.
2000ASPC..207...46M Altcode: 2000ngst.conf...46M
No abstract at ADS
---------------------------------------------------------
Title: Improvements in Ablation Predictions for Reentry-Vehicles
Nosetip
Authors: Couzi, J.; de Winne, J.; Leroy, B.
1999ESASP.426..493C Altcode: 1999asv..conf..493C
No abstract at ADS
---------------------------------------------------------
Title: Zeeman splitting in interstellar molecules. II. The ethynyl
radical
Authors: Bel, N.; Leroy, B.
1998A&A...335.1025B Altcode:
The Zeeman splitting that a longitudinal magnetic field would produce on
the ethynyl radical is calculated for the transitions typical of those
observed in the interstellar clouds. It turns out that the ubiquitous
CCH radical adds to the list of the few interstellar molecules that
could be used to determine magnetic fields in molecular clouds.
---------------------------------------------------------
Title: Electrical properties of the gas within molecular clouds.
Authors: Bel, N.; Leroy, B.
1996A&A...305..598B Altcode:
The electrical properties of the matter within a molecular cloud are
examined. It is verified that, whilst the MHD approximation is still
valid, the dominating presence of neutrals is the source of a very large
anisotropy of the electrical conductivity; indeed, the latter differs in
the directions parallel and perpendicular to the magnetic field by many
orders of magnitude. The implication of this result for the dissipative
processes (e.g., wave dissipation) cannot be underestimated. This
anisotropy prevails during a large part of the evolution of a cloud.
---------------------------------------------------------
Title: The dynamics of the solar convective zone by means of magnetic
tracers
Authors: Collin, B.; Nesme-Ribes, E.; Leroy, B.; Meunier, N.;
Sokoloff, D.
1995CRASB.321..111C Altcode: 1995CRASM.321..111C
The rotation of the sun's convective zone can be studied by using
the motions of magnetic features observed in the solar atmosphere but
deeply rooted. It becomes possible to assign a depth of anchorage to
these magnetic tracers, by helioseismology, which probes solar rotation
layer by layer.
---------------------------------------------------------
Title: Presumptive evidence for a low value of the total ozone
content above Antarctica in September, 1958
Authors: Rigaud, P.; Leroy, B.
1990AnGeo...8..791R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observability of the Magnetic Field in Molecular Clouds
Authors: Bel, N.; Leroy, B.
1990IAUS..140..304B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Zeeman splitting in interstellar molecules.
Authors: Bel, N.; Leroy, B.
1989A&A...224..206B Altcode:
The Zeeman splitting due to a longitudinal magnetic field on some
transitions of diatomic molecules observed in the interstellar clouds
are calculated. Only CN and SO exhibit effects comparable to that of
OH. Their observability in the mm range is discussed. In the same
wavelength range, O2 would exhibit Zeeman effects even larger than
that of OH, but must be observed from space radiotelescopes.
---------------------------------------------------------
Title: Visible absorption cross-sections of NO2 at 298 K and 235 K
Authors: Leroy, B.; Rigaud, P.; Hicks, E.
1987AnGeo...5..247L Altcode:
The absorption cross-sections of NO2 are measured between 426.8 nm
and 449.9 nm in increments of 0.1 nm at temperatures of 298 K and 235
K. The present results are applied to the C.M.S. (Composes Minoritaires
Stratospheriques) spectrometer of the Geneva Observatory.
---------------------------------------------------------
Title: Résolution analytique approchée des équations
différentielles (ordinaires et aux dérivées partielles).
Authors: Leroy, B.
1986mma..conf...33L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Caractère quasi-universel des équations asymptotiques.
Authors: Leroy, B.
1986mma..conf..439L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the derivation of the energy flux of linear
magnetohydrodynamic waves
Authors: Leroy, B.
1985GApFD..32..123L Altcode:
New light is shed on the derivation of the energy flux of the linear
MHD waves. It is shown that, according to a suggestion of Lighthill,
the usual perturbation procedure, which starts from the general
expression for the energy flux, need not be supplemented by an
averaging procedure. As a result, it is shown that to second order in
the wave amplitude, a quantity identifiable as the wave energy flux
is conserved. Some of the subtleties inherent in the derivation of
the perturbation energy equation are discussed.
---------------------------------------------------------
Title: Phase Mixing of Propagating Alfven Waves
Authors: Nocera, L.; Leroy, B.; Priest, E. R.
1985IAUS..107..365N Altcode:
Among MHD waves, Alfvén waves have been proved to be the best
candidates to reach the solar corona and, eventually, to be responsible
for the heating of this outer part of the solar atmosphere. The problem
concerning the mechanism able to transform the energy stored in the
waves into heat is considered.
---------------------------------------------------------
Title: Phase mixing of propagating Alfven waves
Authors: Nocera, L.; Priest, E. R.; Leroy, B.
1984A&A...133..387N Altcode:
The fundamental wave solution found by Heyvaerts and Priest
(1983) for the propagation and damping of shear Alfven waves in an
inhomogeneous medium is checked against their assumptions, and a range
of self-consistency is provided. By analyzing wave behavior outside
this range, novel wave propagation properties are discovered. In the
limit of weak damping, a uniformly valid solution is obtained by the
method of multiple scales. For long wavelengths, the diffusion of
energy in the direction transverse to the wave propagation is found
to be important, and leads to weaker damping laws than those found by
Heyvaerts and Priest.
---------------------------------------------------------
Title: Introduction à la magnétohydrodynamique.
Authors: Leroy, B.
1984cms..conf..123L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Magnetoacoustic Gravity Waves and the Heating of the Solar
Corona
Authors: Leroy, B.
1984apoa.conf..326L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectres d'absorption dans le proche ultraviolet de
CS<SUB>2</SUB> et SO<SUB>2</SUB> entre 200 et 300K
Authors: Leroy, B.; Rigaud, P.; Jourdain, J. L.; Le Bras, G.
1983M&P....29..177L Altcode:
Spectres d'absorption dans le proche ultraviolet de CS<SUB>2</SUB>
et SO<SUB>2</SUB> entre 200 et 300K
---------------------------------------------------------
Title: Propagation of Alfven waves in an isothermal atmosphere when
the displacement current is not neglected
Authors: Leroy, B.
1983A&A...125..371L Altcode:
If the solar atmosphere is modelled by a medium with a (possibly
piece-wise) exponentially decreasing density, permeated by a
uniform magnetic field, for MHD waves with a period ranging between
a few seconds and several hours the WKBJ approximation is nowhere
valid. Consequently, the concept of travelling wave is no longer
meaningful and difficulties arise concerning the boundary condition
that there be no incoming wave from infinity. In the past, these have
been circumvented by confining arbitrarily the inhomogeneous medium to a
region of finite extension. In the present paper the author proposes an
alternative solution devoid of this free parameter; it simply consists
in not discarding the displacement current in Maxwell's equations.
---------------------------------------------------------
Title: Notions générales d'hydrodynamique.
Authors: Leroy, B.
1983ihaa.conf....3L Altcode:
Contents: Introduction. Equations fondamentales. Similitude dynamique
- analyse dimensionnelle. Approximation de Boussinesq - critères de
similitude de la convection. Linéarisation - instabilité.
---------------------------------------------------------
Title: Propagation of Waves in an Atmosphere in the Presence of a
Magnetic Field - Part Six - Application of Magneto-Acoustic Mode
Theory to the Solar Atmosphere
Authors: Schwartz, S. J.; Leroy, B.
1982A&A...112...93S Altcode:
The theory of magneto-acoustic-gravity oscillations in an exponential
atmosphere permeated by a uniform vertical magnetic field, presented by
us in a companion paper, is applied to the solar atmosphere. Numerical
parameters typical of both sunspots and coronal hole regions are used
in our investigations over a wide frequency range of the energy flux
carried by such oscillations from the photosphere to the corona. We
conclude that the combined effects of stratification, partially
transverse propagation and the transition region make it unlikely that
such modes dominate coronal energetics.
---------------------------------------------------------
Title: Propagation of waves in an atmosphere in the presence
of a magnetic field. V - The theory of magneto-acoustic-gravity
oscillations. VI - Application of magneto-acoustic-gravity mode
theory to the solar atmosphere
Authors: Leroy, B.; Schwartz, S. J.
1982A&A...112...84L Altcode:
The study concerns the oscillations and associated energy flux in a
horizontally stratified medium permeated by a uniform vertical magnetic
field parallel to a uniform gravitational field. Particular attention
is given to the obvious applications to sunspots and the corona. In
addition to the Alfven mode, the inhomogeneous analogs of the fast and
slow MHD waves which propagate in a homogeneous medium are found. The
boundary conditions and energy flux calculations that are appropriate
for these modes are discussed, as are some general considerations
of the series solutions themselves. The theory is then applied to
the solar atmosphere. Numerical parameters typical of both sunspots
and coronal hole regions are used in the investigations over a wide
frequency range of the energy flux carried by such oscillations from
the photosphere to the corona. It is concluded that the combined effects
of stratification, partially transverse propagation, and the transition
region make it unlikely that such modes dominate coronal energetics.
---------------------------------------------------------
Title: Coronal oscillations - Energy transport in the sun by
magneto-atmospheric modes
Authors: Leroy, B.
1982PhDT.........1L Altcode:
Errors are demonstrated to exist in an eikonal approximation of the
wave propagation in the solar atmosphere, and possible models for
wave heating of the corona are considered. Consideration is given to
data from the ATM instruments on board Skylab, from the OSO series
satellites, and to studies of other stellar coronas with the IUE and
Einstein Observatory. It is shown that Alfven waves propagating from
the convection zone are not strong enough to heat the solar corona
to the observed levels, which are actually hotter than those in the
photosphere, although the corona has a less dense composition. A zone
is argued to exist where magnetogravitosonic waves emerge in relatively
stable condition, and have been detected in the solar wind. A linear
analysis is presented to identify the region of origin of the upcoming
waves, showing that slow vertical oscillations emerge above sunspots
while slow magnetohydrodynamic waves do not.
---------------------------------------------------------
Title: Propagation of waves in an atmosphere in the presence of a
magnetic field. IV - Alfven waves in sunspot umbrae
Authors: Bel, N.; Leroy, B.
1981A&A...104..203B Altcode:
The propagation of Alfven waves in a sunspot is studied without
the aid of the eikonal approximation. It is found that the outgoing
energy flux density reaching the corona is less than 10 to the -5 of
the input energy flux density. This shows clearly that the cooling
of sunspots by ascending Alfven waves is not possible. In the study,
special attention is given to the transmittance of the atmosphere.
---------------------------------------------------------
Title: Propagation of waves in an atmosphere in the presence of a
magnetic field. III - Alfven waves in the solar atmosphere
Authors: Leroy, B.
1981A&A....97..245L Altcode:
The propagation of Alfven waves is treated within the framework of a
realistic model of the solar atmosphere without recourse to the eikonal
approximation. The very low value of the transmittance (less than 1
percent) indicates that Alfven waves observed in the interplanetary
medium have not been generated in the sun's convection zone. This
conclusion is supported by Pioneer 6 data.
---------------------------------------------------------
Title: Propagation of waves in an atmosphere in the presence of a
magnetic field. II - The reflection of Alfven waves
Authors: Leroy, B.
1980A&A....91..136L Altcode:
The propagation of linear Alfven waves in an isothermal atmosphere is
investigated without the use of the WKBJ approximation. Wave reflection
induced by the density gradient is studied in detail, and special
emphasis is placed on the coupled-modes representation. As an example,
attention is given to the reflectance and transmittance of a slab of
isothermal atmosphere with respect to Alfven waves.
---------------------------------------------------------
Title: Determination of the total content of atmospheric nitrogen
dioxide from ground-based measurements of stellar spectra
Authors: Leroy, B.; Hicks, E.; Vassy, A.
1980AnG....36..205L Altcode:
From the experimental work of A. and E. Vassy (1937) on atmospheric
absorption which was carried out in Morocco, the total atmospheric
content of nitrogen dioxide was determined. The results obtained from
stellar spectra, taken from the ground, vary according to the season
and outline a night decay of NO2. The average value of the total
atmospheric content of NO2 ranges from 5 x 10 to the 16th to 1 x 10
to the 17th molecules/sq cm.
---------------------------------------------------------
Title: Some Comments on the Propagation of Alfven Waves in an
Atmosphere
Authors: Leroy, B.
1980jfss.conf..251L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Reflexion and Transmission of Alfven Waves in an Atmosphere
Authors: Bel, N.; Leroy, B.
1980IAUS...91..131B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Propagation of waves in an atmosphere in the presence of a
magnetic field. I. The method.
Authors: Leroy, B.; Bel, N.
1979A&A....78..129L Altcode:
A method is developed for studying MHD-wave propagation in an
isothermal atmosphere permeated by a uniform magnetic field. The
hydrodynamic Lagrangian for an infinitely conducting and isothermal
atmosphere permeated by an arbitrary magnetic field is examined, the
Euler-Lagrange equations are obtained, and some physical insight into
the terms involved is given. Whitman's (1965) averaged Lagrangian method
is reviewed and applied to magnetoacoustic gravity waves propagating
in an isothermal atmosphere permeated by a uniform magnetic field
arbitrarily oriented with respect to the (constant) gravity field. The
general equations of motion are derived in the linear approximation,
and an analytical method is outlined for solving these equations.
---------------------------------------------------------
Title: A four-filter photometer for the measurement of total ozone
in the atmosphere.
Authors: Leroy, B.
1977JApMe..16.1082L Altcode:
The paper examines the design (optical and electronic), operating
principle and calibration of a photometer which, using four interference
filters and a photocell, is designed for the measurement of total
ozone in the atmosphere from solar light scattered by the zenith
sky. In a 1974 field test the four-filter photometer was compared
to other instruments, particularly the Dobson spectrophotometer. It
was determined that to avoid errors, the photometer data should be
supplemented with a study of the effects of cloud cover, bandwidth
and aerosols on total ozone measurements.
---------------------------------------------------------
Title: Etude statistique des relations entre la radiation X solaire,
les renforcements soudains d'atmosphériques et les plages d'activité
solaire
Authors: Leroy, B.
1977C&T....93..215L Altcode:
A statistical study correlating low-frequency electromagnetic wave
propagation in the ionosphere, solar X-ray radiation and ranges of solar
activity is reported. The level of solar X-ray radiation is found to
correlate with the energetics of the electromagnetic wave propagation;
a background level of Sudden Enhancement of Atmospherics (SEA) and a
higher degree of enhancement are distinguished. Solar activity ranges
determined from Solar Geophysical Data are also correlated to the
SEA levels.
---------------------------------------------------------
Title: Analytical Study of Magnetoacoustic Gravity Waves
Authors: Bel, N.; Leroy, B.
1977A&A....55..239B Altcode:
Summary. An analytical study of magneto-acoustic gravity waves
propagating in an isothermal atmosphere along the gravity field has
been done; we obtain the equation giving the cut-off frequency and
we establish the conditions for the existence of a cross-over in the
dispersion equation. Key words: waves linear coupling magnetic field
gravity solar atmosphere
---------------------------------------------------------
Title: On the Possibility of Nucleosynthesis in Any Matter-Antimatter
Symmetric Cosmology
Authors: Combes, F.; Fassi-Fehri, O.; Leroy, B.
1975Ap&SS..37..151C Altcode:
In any matter-antimatter symmetric cosmology the primeval
nucleosynthesis imposes a typical size of a region of
matter (antimatter) much larger than the diffusion length of
neutrons. Observational results on the abundances of cosmic deuterium
and helium are used to evaluate how large it has to be. As a result
we find that a minimal sizeL <SUB>1</SUB>∼1.5×10<SUP>8</SUP> cm at
the temperatureT=1 MeV is compatible with the standard abundances of
primeval helium and deuterium.
---------------------------------------------------------
Title: Nucleosynthesis in a Symmetrical Universe
Authors: Combes, F.; Fassi-Fehri, O.; Leroy, B.
1975hea..conf..155C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Nucleosynthesis and matter-antimatter cosmologies
Authors: Combes, F.; Fassi-Fehri, O.; Leroy, B.
1975Natur.253...25C Altcode:
IF light elements are of cosmological origin, then a
given cosmological model should be able to reproduce the
observed abundances<SUP>1</SUP>. Symmetric matter-antimatter
cosmologies<SUP>2-4</SUP> do not stand up to this test too well,
and encounter problems whose basis is the annihilation process itself.
---------------------------------------------------------
Title: The Deuterium Puzzle in the Symmetric Universe
Authors: Leroy, B.; Nicolle, J. P.; Schatzman, E.
1973NASSP.339..351L Altcode: 1973gra..conf..351L
No abstract at ADS
