References of "Briquet, Maryline"
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See detailFirst asteroseismic results from CoRoT
Michel, Eric; Baglin, A.; Weiss, W. W. et al

in Communications in Asteroseismology (2008), 156

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 ... [more ▼]

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. [less ▲]

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See detailSpectroscopic observations of pulsating stars
Aerts, C.; Briquet, Maryline ULg; Carrier, F. et al

in Communications in Asteroseismology (2008), 157

During the past three decades, astronomers have been gathering extensive time series of high- precision spectroscopy of pulsating stars. In contrast to one-shot spectra, which provide the fundamental ... [more ▼]

During the past three decades, astronomers have been gathering extensive time series of high- precision spectroscopy of pulsating stars. In contrast to one-shot spectra, which provide the fundamental parameters, time-resolved spectroscopy offers a much broader variety of input for asteroseismology. The most important applications encompass the determination of the radial-velocity amplitudes and phases of the modes, the detection of modes that are invisible in photometry, the identification of the azimuthal orders through specialised methodology, the unravelling of pulsational and orbital motions, and, since a few years, the detection of solar-like oscillations in various types of stars. We discuss the input that spectroscopic time series can provide for asteroseismic modelling, for various types of pulsators. We end with some future prospects of how spectroscopy can help to push seismic applications beyond the present achievements. [less ▲]

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See detailNew insights into the nature of the peculiar star theta Carinae
Hubrig, S.; Briquet, Maryline ULg; Morel, Thierry ULg et al

in Astronomy and Astrophysics (2008), 488

Context: θ Carinae belongs to a group of peculiar early-type stars (OBN) with enhanced nitrogen and carbon deficiency. It is also known as a binary system, but it is not clear yet whether the chemical ... [more ▼]

Context: θ Carinae belongs to a group of peculiar early-type stars (OBN) with enhanced nitrogen and carbon deficiency. It is also known as a binary system, but it is not clear yet whether the chemical anomalies can be explained by mass transfer between the two components. On the basis of the previously reported spectral variability of a few metal lines it may be expected that θ Car possesses a weak magnetic field. <BR />Aims: A study of the physical nature of this hot massive binary which is furthermore a well-known blue straggler lying ~2 mag above the turnoff of the young open cluster IC 2602 is important to understand the origin of its strong chemical anomalies. <BR />Methods: We acquired high resolution spectroscopic and low resolution spectropolarimetric observations to achieve the following goals: a) to improve the orbital parameters to allow a more in-depth discussion on the possibility of mass transfer in the binary system; b) to carry out a non-local thermodynamic equilibrium (NLTE) abundance analysis; and c) to search for the presence of a magnetic field. <BR />Results: The study of the radial velocities using CORALIE spectra allowed us to significantly improve the orbital parameters. A comparative NLTE abundance analysis was undertaken for θ Car and two other early B-type stars with recently detected magnetic fields, Ï Sco and ξ[SUP]1[/SUP] CMa. The analysis revealed significantly different abundance patterns: a one-order-of-magnitude nitrogen overabundance and carbon depletion was found in θ Car, while the oxygen abundance is roughly solar. For the stars ξ[SUP]1[/SUP] CMa and Ï Sco the carbon abundance is solar and, while an N excess is also detected, it is of much smaller amplitude (0.4-0.6 dex). Such an N overabundance is typical of the values already found for other slowly-rotating (magnetic) B-type dwarfs. For θ Car, we attribute instead the chemical peculiarities to a past episode of mass transfer between the two binary components. The results of the search for a magnetic field using FORS 1 at the VLT consisting of 26 measurements over a time span of ~1.2 h are rather inconclusive: only few measurements have a significance level of 3Ï . Although we detect a periodicity of the order of ~8.8 min in the dataset involving the measurements on all hydrogen Balmer lines with the exception of the Hα and Hβ lines, these results have to be confirmed by additional time-resolved magnetic field observations. Based on observations collected with the CORALIE spectrograph attached to the Euler Telescope of the Geneva Observatory located at La Silla (Chile), at the European Southern Observatory, Paranal, Chile (ESO programmes 67.D-0239(A), 072.D-0377(A), 078.D-0080(A) and 278.D-5056(A)), and at the Complejo Astronómico El Leoncito (CASLEO), Argentina. [less ▲]

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See detailGround-based observations of the beta Cephei CoRoT main target HD 180642
Briquet, Maryline ULg; Uytterhoeven, K.; Aerts, C. et al

Conference (2008, July)

We present the preliminary results of a detailed study of ground-based photometric and spectroscopic observations dedicated to the β Cephei CoRoT main target HD 180642. Besides the non-linear dominant ... [more ▼]

We present the preliminary results of a detailed study of ground-based photometric and spectroscopic observations dedicated to the β Cephei CoRoT main target HD 180642. Besides the non-linear dominant radial mode several low-amplitude modes are detected in both kinds of datasets. Our aim is to derive the wavenumbers (ℓ,m) of these modes, as additional constraints to the CoRoT pulsation frequencies, for forthcoming asteroseismic modelling of the star. [less ▲]

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See detailThe moment method
Briquet, Maryline ULg

Learning material (2008)

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See detailMode identification from spectroscopy
Briquet, Maryline ULg

Learning material (2008)

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See detailMagnetic fields in massive stars
Hubrig, S.; Scholler, M.; Briquet, Maryline ULg et al

in Contributions of the Astronomical Observatory Skalnaté Pleso (2008), 38

We review the recent discoveries of magnetic fields in different types of massive stars and briefly discuss strategies for spectropolarimetric observations to be carried out in the future.

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See detailNitrogen enrichment, boron depletion and magnetic fields in slowly-rotating B-type dwarfs
Morel, Thierry ULg; Hubrig, S.; Briquet, Maryline ULg

in Astronomy and Astrophysics (2008), 481

Evolutionary models for massive stars, accounting for rotational mixing effects, do not predict any core-processed material at the surface of B dwarfs with low rotational velocities. Contrary to ... [more ▼]

Evolutionary models for massive stars, accounting for rotational mixing effects, do not predict any core-processed material at the surface of B dwarfs with low rotational velocities. Contrary to theoretical expectations, we present a detailed and fully-homogeneous, NLTE abundance analysis of 20 early B-type dwarfs and (sub)giants that reveals the existence of a population of nitrogen-rich and boron-depleted, yet intrinsically slowly-rotating objects. The low-rotation rate of several of these stars is firmly established, either from the occurrence of phase-locked UV wind line-profile variations, which can be ascribed to rotational modulation, or from theoretical modelling in the pulsating variables. The observational data presently available suggest a higher incidence of chemical peculiarities in stars with a (weak) detected magnetic field. This opens the possibility that magnetic phenomena are important in altering the photospheric abundances of early B dwarfs, even for surface field strengths at the one hundred Gauss level. However, further spectropolarimetric observations are needed to assess the validity of this hypothesis. [less ▲]

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See detailFirst asteroseismic results from CoRoT
Michel, Eric; Baglin, Annie; Weiss, W.W. et al

in Communication in Asteroseismology (2008), 157

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 ... [more ▼]

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. [less ▲]

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See detailHigh-Precision Spectroscopy of Pulsating Stars
Aerts, C.; Hekker, S.; Desmet, M. et al

in Precision Spectroscopy in Astrophysics, Proceedings of the ESO/Lisbon/Aveiro Conference held in Aveiro, Portugal, 11-15 September 2006. (2008)

We review methodologies currently available to interprete time series of high-resolution high-S/N spectroscopic data of pulsating stars in terms of the kind of (non-radial) modes that are excited. We ... [more ▼]

We review methodologies currently available to interprete time series of high-resolution high-S/N spectroscopic data of pulsating stars in terms of the kind of (non-radial) modes that are excited. We illustrate the drastic improvement of the detection treshold of line-profile variability thanks to the advancement of the instrumentation over the past two decades. This has led to the opportunity to interprete line-profile variations with amplitudes of order m/s, which is a factor 1000 lower than the earliest line-profile time series studies allowed for. [less ▲]

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See detailThe Chemical Composition of B-type Pulsators: Some Unexpected Results
Morel, Thierry ULg; Briquet, Maryline ULg; Aerts, C.

in Precision Spectroscopy in Astrophysics (2008)

We present a project aimed at self-consistently deriving the physical parameters and chemical composition of massive pulsators (β, Cephei stars, Slowly Pulsating B stars) based on high-resolution optical ... [more ▼]

We present a project aimed at self-consistently deriving the physical parameters and chemical composition of massive pulsators (β, Cephei stars, Slowly Pulsating B stars) based on high-resolution optical spectra. Such data will be essential for a proper theoretical interpretation of their oscillation spectrum, but may also contribute in a broader context to our understanding of mixing and diffusion processes in B-type stars. As an illustration, our first results reveal the existence of core-processed material at the surface of some slowly-rotating β, Cephei stars which is not predicted by current evolutionary models including rotation. [less ▲]

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See detailA comparative study of B-type pulsators and non-pulsating chemically peculiar Bp stars
Briquet, Maryline ULg; Hubrig, S.; De Cat, P. et al

in Communications in Asteroseismology (2007), 150

We carry out a comparative study between a sample of confirmed and well-studied B-type pulsators and a sample of well-studied Bp stars with known periods and magnetic field strengths. Our study indicates ... [more ▼]

We carry out a comparative study between a sample of confirmed and well-studied B-type pulsators and a sample of well-studied Bp stars with known periods and magnetic field strengths. Our study indicates that the group of Bp stars is younger than the group of SPB stars and that stars with stronger magnetic fields have much lower pulsation amplitudes. [less ▲]

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See detailA spectroscopic study of the β Cephei star 12 (DD) Lacertae
Desmet, M.; Briquet, Maryline ULg; De Cat, P. et al

in Communications in Asteroseismology (2007), 150

We present first results of a spectroscopic multisite campaign for 12 (DD) Lacertae (hereinafter 12 Lac). This star is one of the best observed β Cephei stars. It has a large number of known oscillation ... [more ▼]

We present first results of a spectroscopic multisite campaign for 12 (DD) Lacertae (hereinafter 12 Lac). This star is one of the best observed β Cephei stars. It has a large number of known oscillation frequencies but a lack of identified m-values for its detected modes. In our data set we find seven independent frequencies together with combination frequencies. In addition, two of these modes are identified: one radial mode and one prograde dipole mode. [less ▲]

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See detailAsteroseismology of the β Cephei star KP Per
Saesen, S.; Briquet, Maryline ULg; Cuypers, J. et al

in Communications in Asteroseismology (2007), 150

We investigated the oscillations of the β Cephei star KP Per (HD 21803, B2IV, V=6.41) using Geneva photometry. We performed a detailed frequency analysis and a mode identification by means of photometric ... [more ▼]

We investigated the oscillations of the β Cephei star KP Per (HD 21803, B2IV, V=6.41) using Geneva photometry. We performed a detailed frequency analysis and a mode identification by means of photometric amplitude ratios. Then we confronted our deduced observational oscillation spectrum with that predicted by theory in order to determine a range for some stellar parameters, such as the mass and radius of KP Per. [less ▲]

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See detailAn abundance analysis of slowly pulsating B stars
Briquet, Maryline ULg; Morel, Thierry ULg

in Communications in Asteroseismology (2007), 150

We present the methodology and the first results of a study aimed to determine in a self-consistent way the physical parameters T_{eff} and log g as well as NLTE abundances of the majority of all ... [more ▼]

We present the methodology and the first results of a study aimed to determine in a self-consistent way the physical parameters T_{eff} and log g as well as NLTE abundances of the majority of all confirmed slowly pulsating B stars (hereafter SPBs). [less ▲]

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See detailNitrogen excess in slowly-rotating beta Cephei stars: deep mixing or diffusion?
Morel, Thierry ULg; Butler, K.; Aerts, C. et al

in Communications in Asteroseismology (2007), 150

We present the results of an NLTE abundance study of a small sample of β Cephei stars, which point to the existence of a population of slowly-rotating B-type pulsators exhibiting a significant amount of ... [more ▼]

We present the results of an NLTE abundance study of a small sample of β Cephei stars, which point to the existence of a population of slowly-rotating B-type pulsators exhibiting a significant amount of nitrogen-enriched material at their surface. Although the origin of this nitrogen excess remains unclear, an overabundance preferentially occurring in stars with a detected magnetic field seems to emerge at this stage. Full details can be found in Morel et al. (2006). [less ▲]

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See detailOn the co-existence of chemically peculiar Bp stars, slowly pulsating B stars and constant B stars in the same part of the HR diagram
Briquet, Maryline ULg; Hubrig, S.; De Cat, P. et al

in Astronomy and Astrophysics (2007), 466

Aims: In order to better model massive B-type stars, we need to understand the physical processes taking place in slowly pulsating B (SPB) stars, chemically peculiar Bp stars, and non-pulsating normal B ... [more ▼]

Aims: In order to better model massive B-type stars, we need to understand the physical processes taking place in slowly pulsating B (SPB) stars, chemically peculiar Bp stars, and non-pulsating normal B stars co-existing in the same part of the H-R diagram. <BR />Methods: We carry out a comparative study between samples of confirmed and well-studied SPB stars and a sample of well-studied Bp stars with known periods and magnetic field strengths. We determine their evolutionary state using accurate HIPPARCOS parallaxes and Geneva photometry. We discuss the occurrence and strengths of magnetic fields as well as the occurrence of stellar pulsation among both groups. Further, we make a comparison of Geneva photometric variability for both kinds of stars. <BR />Results: The group of Bp stars is significantly younger than the group of SPB stars. Longitudinal magnetic fields in SPB stars are weaker than those of Bp stars, suggesting that the magnetic field strength is an important factor for B type stars to become chemically peculiar. The strongest magnetic fields appear in young Bp stars, indicating a magnetic field decay in stars at advanced ages. Rotation periods of Bp and pulsation periods of SPB stars are of the same order and the behaviour of Geneva photometric variability of some Bp stars cannot be distinguished from the variability of SPB stars, illustrating the difficulty to interpret the observed variability of the order of days for B-type stars. We consider the possibility that pulsation could be responsible for the variability among chemically peculiar stars. In particular, we show that a non-linear pulsation model is not excluded by photometry for the Bp star HD 175362. [less ▲]

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See detailDiscovery of Magnetic Fields in Slowly Pulsating B Stars
Hubrig, S.; Briquet, Maryline ULg; Schöller, M. et al

in Active OB-Stars: Laboratories for Stellar and Circumstellar Physics, ASP Conference Series, Vol. 361, Proceedings of the conference held 29 August - 2 September, 2005 at Hokkai-Gakuen University, Sapporo, Japan. (2007, March 01)

We present the first observations and conclusions of a magnetic survey with FORS 1 at the VLT of a sample of 25 Slowly Pulsating B stars. A clear mean longitudinal magnetic field of the order of a few ... [more ▼]

We present the first observations and conclusions of a magnetic survey with FORS 1 at the VLT of a sample of 25 Slowly Pulsating B stars. A clear mean longitudinal magnetic field of the order of a few hundred Gauss was detected in eleven SPBs. Among them several SPBs show a magnetic field that varies in time. It becomes clear that SPBs cannot be regarded anymore as non-magnetic stars. [less ▲]

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