References of "Briquet, Maryline"
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See detailAn asteroseismic study of the beta Cephei CoRoT main target HD 180642: results from the ground-based campaign
Briquet, Maryline ULg; Uytterhoeven, K.; Morel, Thierry ULg et al

in American Institute of Physics Conference Series (2009, September 01)

The β Cephei star HD 180642 was observed by the CoRoT satellite during a run of 156 days in 2007. The space white light photometry revealed the rich frequency spectrum of the star (Degroote et al. 2009 ... [more ▼]

The β Cephei star HD 180642 was observed by the CoRoT satellite during a run of 156 days in 2007. The space white light photometry revealed the rich frequency spectrum of the star (Degroote et al. 2009). In the present study, we provide additional information on the target, based on both ground-based multi-colour photometry and high-resolution spectroscopy. We place our object in the (T[SUB]eff[/SUB], log g) diagram. In addition, we derive the chemical abundances of several elements as well as the metallicity of HD 180642. Finally, we put constraints on the identification of some modes. All these observational constraints will be used to compute stellar models of the target. [less ▲]

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See detailThe evolution of magnetic fields in early B-type stars
Hubrig, S.; Briquet, Maryline ULg; Scholler, M. et al

in Revista Mexicana de Astronomia y Astrofisica Conference Series (2009, August 01)

To date, only a small number of O and early B-type stars have been investigated for magnetic fields, and as a result, only about a dozen magnetic early B-type stars and only few magnetic O stars are known ... [more ▼]

To date, only a small number of O and early B-type stars have been investigated for magnetic fields, and as a result, only about a dozen magnetic early B-type stars and only few magnetic O stars are known. The lack of information on the existence, origin and role of magnetic fields in massive stars is especially disturbing because magnetic fields may have paramount influence on the stellar evolution of high-mass stars. Our study focuses on the magnetic fields in early B-type stars with a stronger emphasis on beta Cep and SPB stars. Weak longitudinal magnetic fields (up to Ë 300 G) have been recently detected using FORS 1 in a few beta Cep and SPB stars, proving that these types of massive B-type stars can no longer be considered as non-magnetic. [less ▲]

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See detailSpace observations of B stars with CoRoT
Degroote, P.; Miglio, Andrea ULg; Debosscher, J. et al

in Communications in Asteroseismology (2009), 158

We present the preliminary results of the exploration of pulsating B stars observed with the CoRoT space mission. The previously known group of Slowly Pulsating B stars gains a substantial amount of new ... [more ▼]

We present the preliminary results of the exploration of pulsating B stars observed with the CoRoT space mission. The previously known group of Slowly Pulsating B stars gains a substantial amount of new candidates, offering the opportunity to test stellar models beyond individual cases. Besides these well-defined stars, the analysis of other B star candidate pulsators hints towards the presence of different variability behaviour, co-existing in the same space in terms of the timescale of the variations and location in the (Teff, logg) diagram. [less ▲]

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See detailAn asteroseismic study of the β Cephei star 12 Lacertae: multisite spectroscopic observations, mode identification and seismic modelling
Desmet, M.; Briquet, Maryline ULg; Thoul, Anne ULg et al

in Monthly Notices of the Royal Astronomical Society (2009), 396

We present the results of a spectroscopic multisite campaign for the β Cephei star 12 (DD) Lacertae. Our study is based on more than thousand high-resolution high S/N spectra gathered with eight different ... [more ▼]

We present the results of a spectroscopic multisite campaign for the β Cephei star 12 (DD) Lacertae. Our study is based on more than thousand high-resolution high S/N spectra gathered with eight different telescopes in a time span of 11 months. In addition, we make use of numerous archival spectroscopic measurements. We confirm 10 independent frequencies recently discovered from photometry, as well as harmonics and combination frequencies. In particular, the slowly pulsating B-stars (SPB)-like g-mode with frequency 0.3428d[SUP]-1[/SUP] reported before is detected in our spectroscopy. We identify the four main modes as (l[SUB]1[/SUB], m[SUB]1[/SUB]) = (1, 1), (l[SUB]2[/SUB], m[SUB]2[/SUB]) = (0, 0), (l[SUB]3[/SUB], m[SUB]3[/SUB]) = (1, 0) and (l[SUB]4[/SUB], m[SUB]4[/SUB]) = (2, 1) for f[SUB]1[/SUB] = 5.178964d[SUP]-1[/SUP], f[SUB]2[/SUB] = 5.334224d[SUP]-1[/SUP], f[SUB]3[/SUB] = 5.066316d[SUP]-1[/SUP] and f[SUB]4[/SUB] = 5.490133d[SUP]-1[/SUP], respectively. Our seismic modelling shows that f[SUB]2[/SUB] is likely the radial first overtone and that the core overshooting parameter α[SUB]ov[/SUB] is lower than 0.4 local pressure scale heights. [less ▲]

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See detailSimultaneous MOST photometry and high-resolution spectroscopy of Spica, a binary system with a massive beta Cephei star component
Desmet, M.; Walker, G.; Yang, S. et al

in Communications in Asteroseismology (2009), 158

We present the data from a unique observational study of Spica, a binary system with a primary component of β Cephei type. We exploit simultaneous high-resolution spectroscopic observations and high ... [more ▼]

We present the data from a unique observational study of Spica, a binary system with a primary component of β Cephei type. We exploit simultaneous high-resolution spectroscopic observations and high-precision photometry obtained by the MOST satellite. By disentangling the spectra of this binary, we get an accurate determination of the orbit. Future work includes a full seismic analysis of the system. [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

in Communications in Asteroseismology (2009), 158

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 (â ,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 detailCoRot B star frequency analysis (Degroote+, 2009)
Degroote, P.; Aerts, C.; Ollivier, M. et al

Computer development (2009)

Results of frequency analyses for 352 candidate B pulsators (candidate Be stars are ommitted) from CoRoT's initial run. For each star, the following information is given: frequency number, amplitude ... [more ▼]

Results of frequency analyses for 352 candidate B pulsators (candidate Be stars are ommitted) from CoRoT's initial run. For each star, the following information is given: frequency number, amplitude + error, frequency value + error, phase + error. The error values for large amplitude frequencies can be slightly underestimated, as they are not corrected for correlation effects. Also given are comments about every frequency: if they are expected to be due to instrumental effects (e.g. orbit of the satellite), if they are harmonics or higher order combinations of previously identified frequencies. (2 data files). [less ▲]

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See detailNew magnetic field measurements of beta Cephei stars and slowly pulsating B stars
Hubrig, Swetlana; Briquet, Maryline ULg; De Cat, P. et al

in IAU Symposium (2009, April 01)

We present the results of the continuation of our magnetic survey with FORS 1 at the VLT of a sample of B-type stars consisting of confirmed or candidate β Cephei stars and Slowly Pulsating B stars ... [more ▼]

We present the results of the continuation of our magnetic survey with FORS 1 at the VLT of a sample of B-type stars consisting of confirmed or candidate β Cephei stars and Slowly Pulsating B stars. Roughly one third of the studied β Cephei stars have detected magnetic fields. The fraction of magnetic Slowly Pulsating B and candidate Slowly Pulsating B stars is found to be higher, up to 50%. We find that the domains of magnetic and non-magnetic pulsating stars in the H-R diagram largely overlap, and no clear picture emerges as to the possible evolution of the magnetic field across the main sequence. [less ▲]

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See detailNew magnetic field measurements of beta Cephei stars and slowly pulsating B stars
Hubrig, S.; Briquet, Maryline ULg; De Cat, P. et al

in Astronomische Nachrichten (2009), 330

We present the results of the continuation of our magnetic survey with FORS 1 at the VLT of a sample of B-type stars consisting of confirmed or candidate β Cephei stars and Slowly Pulsating B (hereafter ... [more ▼]

We present the results of the continuation of our magnetic survey with FORS 1 at the VLT of a sample of B-type stars consisting of confirmed or candidate β Cephei stars and Slowly Pulsating B (hereafter SPB) stars, along with a small number of normal B-type stars. A weak mean longitudinal magnetic field of the order of a few hundred Gauss was detected in three β Cephei stars and two stars suspected to be β Cephei stars, in five SPB stars and eight stars suspected to be SPB stars. Additionally, a longitudinal magnetic field at a level larger than 3Ï has been diagnosed in two normal B-type stars, the nitrogen-rich early B-type star HD 52089 and in the B5 IV star HD 153716. Roughly one third of β Cephei stars have detected magnetic fields: Out of 13 β Cephei stars studied to date with FORS 1, four stars possess weak magnetic fields, and out of the sample of six suspected β Cephei stars two show a weak magnetic field. The fraction of magnetic SPBs and candidate SPBs is found to be higher: Roughly half of the 34 SPB stars have been found to be magnetic and among the 16 candidate SPBs eight stars possess magnetic fields. In an attempt to understand why only a fraction of pulsating stars exhibit magnetic fields, we studied the position of magnetic and non-magnetic pulsating stars in the H-R diagram. We find that their domains in the H-R diagram largely overlap, and no clear picture emerges as to the possible evolution of the magnetic field across the main sequence. It is possible that stronger fields tend to be found in stars with lower pulsating frequencies and smaller pulsating amplitudes. A somewhat similar trend is found if we consider a correlation between the field strength and the v sin i-values, i.e. stronger magnetic fields tend to be found in more slowly rotating stars. Based on observations obtained at the European Southern Observatory, Paranal, Chile (ESO programmes 078.D-0140(A), 078.D-0330(A), 079.D-0241(A), and 080.D-0383(A)). [less ▲]

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See detailStudying the Magnetic Properties of Upper Main-sequence Stars with FORS1
Hubrig, Swetlana; Scholler, Markus; Briquet, Maryline ULg et al

in The Messenger (2009), 135

We summarise the results of our recent magnetic field studies in upper main-sequence stars, which have exploited the spectropolarimetric capability of FORS1 at the VLT extensively.

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See detailThe Beta Cephei star HD 180642: Full integration of CoRoT and ground data for mode identification
Briquet, Maryline ULg

Conference (2009, February)

The B1.5 II-III star HD 180642 is the only known Beta Cephei star in CoRoT’s core programme. To complement the space data of this target, both ground-based photometric and spectroscopic data were ... [more ▼]

The B1.5 II-III star HD 180642 is the only known Beta Cephei star in CoRoT’s core programme. To complement the space data of this target, both ground-based photometric and spectroscopic data were collected, to which we added several archival observations. In this talk, we describe our results from a full integration of CoRoT and intensive ground-based observations. The star is a non-linear dominant radial mode pulsator for which low-amplitude modes are detected for the fi rst time. A few of the latter are observed in our ground-based datasets so that a mode identifi cation for them is possible. To this end state-of-the-art techniques are adapted to be applied to a star with a highly non-linear behaviour of the radial mode. Additionally, a careful interpretation of the CoRoT lightcurve helps to identify the wavenumbers. Besides this outcome, the Van Hoof effect for the dominant mode is investigated and the stellar parameters and chemical abundances are determined. All this information is to be used as additional constraints to the CoRoT pulsation frequencies, for asteroseismic modelling of this Beta Cephei star. Additional abstracts cover the lightcurve modelling of this pulsator (Degroote et al.) as well as seismic modelling (Thoul et al.). [less ▲]

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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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