Publications (50)
CRIRES high-resolution infrared spectroscopy of the long-period Cepheid l Car
N. Nardetto, E. Poretti, A. Gallenne +17
The dynamical structure of the atmosphere of Cepheids has been well studied in the optical. Several authors have found very interesting spectral features in the J band, but little…
A new method for the spectroscopic identification of stellar non-radial pulsation modes. II. Mode identification of the Delta Scuti star FG Virginis
W. Zima, D. Wright, J. Bentley +7
We present a mode identification based on new high-resolution time-series spectra of the non-radially pulsating Delta Scuti star FG~Vir (HD 106384, V = 6.57, A5V). From 2002 Februa…
The tip of the iceberg: the frequency content of the Delta Sct star HD 50844 from CoRoT space photometry
E. Poretti, L. Mantegazza, M. Rainer +19
It has been suggested that the detection of a wealth of very low amplitude modes in Delta Sct stars was only a matter of signal--to--noise ratio. Access to this treasure, impossibl…
Asteroseismology and Interferometry
M. S. Cunha, C. Aerts, J. Christensen-Dalsgaard +22
Asteroseismology provides us with a unique opportunity to improve our understanding of stellar structure and evolution. Recent developments, including the first systematic studies…
SiO maser polarization and magnetic field in evolved cool stars
L. Marinho, F. Herpin, H. Wiesemeyer +6
Both magnetic fields and photospheric/atmospheric dynamics can be involved in triggering the important mass loss observed in evolved cool stars. Previous works have revealed that t…
Understanding the dynamical structure of pulsating stars. HARPS spectroscopy of the delta Scuti stars rho Pup and DX Cet
N. Nardetto, E. Poretti, M. Rainer +4
High-resolution spectroscopy is a powerful tool to study the dynamical structure of pulsating stars atmosphere. We aim at comparing the line asymmetry and velocity of the two delta…
Multiperiodicity in the newly discovered mid-late Be star V2104 Cygni
K. Uytterhoeven, E. Poretti, E. Rodriguez +5
We obtained the first long, homogenous time-series of V2104Cyg, consisting of 679 datapoints, with the uvbybeta photometers of Sierra Nevada and San Pedro Martir Observatories with…
Evolution of the magnetic field of Betelgeuse from 2009 - 2017
P. Mathias, M. Aurière, A. López Ariste +14
Betelgeuse is an M-type supergiant that presents a circularly polarized (Stokes V) signal in its line profiles, interpreted in terms of a surface magnetic field. The weak circular…
Gamma Dor and Gamma Dor - Delta Sct Hybrid Stars In The CoRoT LRa01
M. Hareter, P. Reegen, A. Miglio +7
A systematic search for gamma Dor and gamma Dor - delta Scuti hybrid pulsators was conducted on the CoRoT LRa01 Exo-archive yielding a total of 418 gamma Dor and 274 hybrid candida…
Close-up of primary and secondary asteroseismic CoRoT targets and the ground-based follow-up observations
K. Uytterhoeven, E. Poretti, M. Rainer +13
To optimise the science results of the asteroseismic part of the CoRoT satellite mission a complementary simultaneous ground-based observational campaign is organised for selected…
An in-depth study of HD 174966 with CoRoT photometry and HARPS spectroscopy. Large separation as a new observable for δSct stars
A. GarcÃa Hernández, A. Moya, E. Michel +18
The aim of this work was to use a multi-approach technique to derive the most accurate values possible of the physical parameters of the δSct star HD174966. In addition, we search…
Discovery of a complex linearly polarized spectrum of Betelgeuse dominated by depolarization of the continuum
M. Aurière, A. López Ariste, P. Mathias +15
Betelgeuse is an M supergiant that harbors spots and giant granules at its surface and presents linear polarization of its continuum. We have previously discovered linear polarizat…
HD 50844: the new look of Delta Sct stars from CoRoT space photometry
E. Poretti, E. Michel, R. Garrido +21
It has also been suggested that the detection of a wealth of very low amplitude modes in Delta Sct stars was only a matter of signal--to--noise ratio. Access to this treasure, impo…
Multi-site, multi-technique survey of Gamma Doradus candidates
P. Mathias, J. -M. Le Contel, E. Chapellier +14
We present the first results of a 2-year high-resolution spectroscopy campaign of 59 candidate Gamma Doradus stars which were mainly discovered from the HIPPARCOS astrometric missi…
HD 51106 and HD 50747: an ellipsoidal binary and a triple system observed with CoRoT
N. Dolez, S. Vauclair, E. Michel +13
We present an analysis of the observations of HD 51106 and HD 50747 by the satellite CoRoT, obtained during its initial run, and of the spectroscopic preparatory observations. AIMS…
Pollux: A weak dynamo-driven dipolar magnetic field and implications for its probable planet
M. Aurière, P. Petit, P. Mathias +7
Context: Pollux is considered as an archetype of a giant star hosting a planet. We then discovered a weak magnetic field at its surface using spectropolarimetry. Aims and Methods:…
The asteroseismic ground-based observational counterpart of CoRoT
K. Uytterhoeven, E. Poretti, P. Mathias +13
We present different aspects of the ground-based observational counterpart of the CoRoT satellite mission. We give an overview of the selected asteroseismic targets, the numerous i…
Understanding the dynamical structure of pulsating stars: The Baade-Wesselink projection factor of the delta Scuti stars AI Vel and beta Cas
G. Guiglion, N. Nardetto, P. Mathias +6
Aims. The Baade-Wesselink method of distance determination is based on the oscillations of pulsating stars. The key parameter of this method is the projection factor used to conver…
The CoRoT star ID100866999: a hybrid gamma Doradus - delta Scuti star in an eclipsing binary system
E. Chapellier, P. Mathias
The presence of g- and p-modes allows testing stellar models from the core to the envelope. Moreover, binarity in an eclipsing system constrains the physical parameters of the puls…
An investigation of the close environment of beta Cep with the VEGA/CHARA interferometer
N. Nardetto, D. Mourard, I. Tallon-Bosc +22
High-precision interferometric measurements of pulsating stars help to characterize their close environment. In 1974, a close companion was discovered around the pulsating star bet…
VEGA/CHARA interferometric observations of Cepheids. I. A resolved structure around the prototype classical Cepheid delta Cep in the visible spectral range
N. Nardetto, A. Mérand, D. Mourard +23
The B-W method is used to determine the distance of Cepheids and consists in combining the angular size variations of the star, as derived from infrared surface-brightness relation…
Hybrid gamma Doradus - delta Scuti pulsators: New insights into the physics of the oscillations from Kepler observations
A. Grigahcene, V. Antoci, L. Balona +39
Observations of the pulsations of stars can be used to infer their interior structure and test theoretical models. The main sequence Doradus (Dor) and Scuti (Sct) stars w…
Preparing the COROT space mission: incidence and characterisation of pulsation in the Lower Instability Strip
E. Poretti, R. Garrido, P. J. Amado +24
By pursuing the goal to find new variables in the COROT field-of-view we characterised a sample of stars located in the lower part of the instability strip. Our sample is composed…
An asteroseismic study of the beta Cephei star 12 Lacertae: multisite spectroscopic observations, mode identification and seismic modelling
M. Desmet, M. Briquet, A. Thoul +14
We present the results of a spectroscopic multisite campaign for the beta Cephei star 12 (DD) Lacertae. Our study is based on more than thousand high-resolution high S/N spectra ga…
Ground-based observations of Kepler asteroseismic targets
K. Uytterhoeven, R. Szabo, J. Southworth +42
We present the ground-based activities within the different working groups of the Kepler Asteroseismic Science Consortium (KASC). The activities aim at the systematic characterizat…
The gamma Dor CoRoT target HD49434. I-Results from the ground-based campaign
K. Uytterhoeven, P. Mathias, E. Poretti +22
Context: We present the results of an extensive ground-based photometric and spectroscopic campaign on the gamma Dor CoRoT target HD49434. This campaign was preparatory to the CoRo…
HARPS-N high spectral resolution observations of Cepheids I. The Baade-Wesselink projection factor of δ Cep revisited
N. Nardetto, E. Poretti, M. Rainer +13
The projection factor p is the key quantity used in the Baade-Wesselink (BW) method for distance determination; it converts radial velocities into pulsation velocities. Several met…
Photometric and spectroscopic variability of the B5IIIe star HD 171219
L. Andrade, E. Janot-Pacheco, M. Emilio +11
We analyzed the star HD 171219, one of the relatively bright Be stars observed in the seismo field of the CoRoT satellite, in order to determine its physical and pulsation characte…
Preparing the COROT space mission: new variable stars in the galactic Anticenter direction
E. Poretti, R. Alonso, P. J. Amado +15
The activities related to the preparation of the asteroseismic, photometric space mission COROT are described. Photoelectric observations, wide--field CCD photometry, uvbyB calibra…
Convective cells in Betelgeuse: imaging through spectropolarimetry
A. López Ariste, P. Mathias, B. Tessore +7
We assess the ability to image the photosphere of red supergiants and, in particular Betelgeuse, through the modelling of the observed linear polarization in atomic spectral lines.…
The Kepler characterization of the variability among A- and F-type stars. I. General overview
K. Uytterhoeven, A. Moya, A. Grigahcene +38
The Kepler spacecraft is providing time series of photometric data with micromagnitude precision for hundreds of A-F type stars. We present a first general characterization of the…
A search for magnetic Scuti stars in Kepler hybrid candidates
K. Thomson-Paressant, C. Neiner, P. Lampens +4
Numerous candidate hybrid stars of type Scuti - Doradus have been identified with the Kepler satellite. However, many of them lie outside the theoretically expected insta…
Detection of solar-like oscillations in the bright red giant stars Psc and Tau from a 190-day high-precision spectroscopic multisite campaign
P. G. Beck, E. Kambe, M. Hillen +35
Red giants are evolved stars which exhibit solar-like oscillations. Although a multitude of stars have been observed with space telescopes, only a handful of red-giant stars were t…
Pulsation spectrum of Delta Sct stars: the binary HD 50870 as seen with CoRoT and HARPS
L. Mantegazza, E. Poretti, E. Michel +14
We present the results obtained with the CoRoT satellite for HD 50870, a Delta Sct star which was observed for 114.4 d. The 307,570 CoRoT datapoints were analysed with different te…
Direct constraint on the distance of y2 Velorum from AMBER/VLTI observations
F. Millour, R. G. Petrov, O. Chesneau +95
In this work, we present the first AMBER observations, of the Wolf-Rayet and O (WR+O) star binary system y2 Velorum. The AMBER instrument was used with the telescopes UT2, UT3, and…
The CoRoT B-type binary HD50230: a prototypical hybrid pulsator with g-mode period and p-mode frequency spacings
P. Degroote, C. Aerts, E. Michel +14
B-type stars are promising targets for asteroseismic modelling, since their frequency spectrum is relatively simple. We deduce and summarise observational constraints for the hybri…
HD172189: another step in furnishing one of the best laboratories known for asteroseismic studies
O. L. Creevey, K. Uytterhoeven, S. MartÃn-Ruiz +25
HD172189 is a spectroscopic eclipsing binary system with a rapidly-rotating pulsating delta Scuti component. It is also a member of the open cluster IC4756. These combined characte…
Extensive study of HD 25558, a long-period double-lined binary with two SPB components
Ã. Sódor, P. De Cat, D. J. Wright +33
We carried out an extensive observational study of the Slowly Pulsating B (SPB) star, HD 25558. The ~2000 spectra obtained at different observatories, the ground-based and MOST sat…
CoRoT photometry and high-resolution spectroscopy of the interacting eclipsing binary AU Mon
M. Desmet, Y. Fr'emat, F. Baudin +15
Analyses of very accurate CoRoT space photometry, past Johnson V photoelectric photometry and high-resolution échelle spectra led to the determination of improved and consistent f…
Strong interactions between g- and p-modes in the hybrid gamma Doradus-delta Scuti CoRoT star ID105733033
E. Chapellier, P. Mathias, W. W. Weiss +2
CoRoT ID 105733033 is an excellent example of hybrid pulsators as it shows g- and p-modes with almost similar amplitudes in two clearly distinct frequency domains. Classical Fourie…
gamma Doradus stars in the COROT exoplanets fields: first inspection
P. Mathias, E. Chapellier, M. Bouabid +6
We present here preliminary results concerning 32 stars identified as main gamma Doradus candidates by the COROT Variable Classifier (CVC) among the 4 first fields of the exoplanet…
The close circumstellar environment of Betelgeuse. IV. VLTI/PIONIER interferometric monitoring of the photosphere
M. Montargès, P. Kervella, G. Perrin +9
Context. The mass-loss mechanism of cool massive evolved stars is poorly understood. The proximity of Betelgeuse makes it an appealing target to study its atmosphere, map the shape…
Quasiperiodic patterns in Scuti stars: an in-depth study of the CoRoT star HD 174966
A. GarcÃa Hernández, A. Moya, J. C. Suárez +9
In this work, we have gone one step further from the study presented in the first CoRoT symposium. Our analysis consists on constructing a model database covering the entire uncert…
Understanding the dynamical structure of pulsating stars: The center-of-mass velocity and the Baade-Wesselink projection factor of the beta-Cephei star alpha-Lupi
N. Nardetto, P. Mathias, A. Fokin +5
High-resolution spectroscopy of pulsating stars is a powerful tool to study the dynamical structure of their atmosphere. Lines asymmetry is used to derive the center-of-mass veloci…
The variability of the CoRoT target HD171834: gamma Dor pulsations and/or activity?
K. Uytterhoeven, P. Mathias, A. Baglin +15
We present the preliminary results of a frequency and line-profile analysis of the CoRoT gamma Dor candidate HD171834. The data consist of 149 days of CoRoT light curves and a grou…
Seismic and spectroscopic analysis of 9 bright red giants observed by Kepler
H. R. Coelho, A. Miglio, T. Morel +21
Photometric time series gathered by space telescopes such as CoRoT and Kepler allow to detect solar-like oscillations in red-giant stars and to measure their global seismic constra…
Ground-based observations of the beta Cephei CoRoT main target HD 180642: abundance analysis and mode identification
M. Briquet, K. Uytterhoeven, T. Morel +20
The known beta Cephei star HD 180642 was observed by the CoRoT satellite in 2007. From the very high-precision light curve, its pulsation frequency spectrum could be derived for th…
A long-term study of the magnetic field and activity in the M giant RZ Ari
R. Konstantinova-Antova, S. Georgiev, A. Lèbre +12
We present a detailed long-term study of the single M6 III giant RZ~Ari to obtain direct and simultaneous measurements of the magnetic field, activity indicators, and radial veloci…
Detection of Solar-Like Oscillations, Observational Constraints, and Stellar Models for Cyg, the Brightest Star Observed by the {\it Kepler} Mission
J. A. Guzik, G. Houdek, W. J. Chaplin +52
Cygni is an F3 spectral-type main-sequence star with visual magnitude V=4.48. This star was the brightest star observed by the original Kepler spacecraft mission. Short-cadenc…
Atmospheric Abundances in Post-AGB candidates of Intermediate Temperature
A. Arellano Ferro, Sunetra Giridhar, P. Mathias
Detailed atmospheric abundances have been calculated for a sample of A-G supergiant stars with IR fluxes and/or high galactic latitudes. HD 172481 and HD 158616 show clear indicati…