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See detailMagnetic fields in O-, B- and A-type stars on the main sequence
Briquet, Maryline ULg

in CoRoT Symposium 3 / Kepler KASC-7 joint meeting (in press)

In this review, the latest observational results on magnetic fields in main-sequence stars with radiative envelopes are summarised together with the theoretical works aimed at explaining them.

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See detailThe B Fields in OB Stars (BOB) Survey
Morel, Thierry ULg; Castro, N.; Fossati, L. et al

in IAU Symposium (in press)

The B fields in OB stars (BOB) survey is an ESO large programme collecting spectropolarimetric observations for a large number of early-type stars in order to study the occurrence rate, properties, and ... [more ▼]

The B fields in OB stars (BOB) survey is an ESO large programme collecting spectropolarimetric observations for a large number of early-type stars in order to study the occurrence rate, properties, and ultimately the origin of magnetic fields in massive stars. As of July 2014, a total of 98 objects were observed over 20 nights with FORS2 and HARPSpol. Our preliminary results indicate that the fraction of magnetic OB stars with an organised, detectable field is low. This conclusion, now independently reached by two different surveys, has profound implications for any theoretical model attempting to explain the field formation in these objects. We discuss in this contribution some important issues addressed by our observations (e.g., the lower bound of the field strength) and the discovery of some remarkable objects. [less ▲]

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See detailCombining seismology and spectropolarimetry of hot stars
Neiner, Coralie; Briquet, Maryline ULg; Mathis, Stéphane et al

in IAU Symosium 307 (in press)

Asteroseismology and spectropolarimetry have allowed us to progress significantly in our understanding of the physics of hot stars over the last decade. It is now possible to combine these two techniques ... [more ▼]

Asteroseismology and spectropolarimetry have allowed us to progress significantly in our understanding of the physics of hot stars over the last decade. It is now possible to combine these two techniques to learn even more information about hot stars and constrain their models. While only a few magnetic pulsating hot stars are known as of today and have been studied with both seismology and spectropolarimetry, new opportunities - in particular Kepler2 and BRITE - are emerging and will allow us to rapidly obtain new combined results. [less ▲]

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See detailB fields in OB stars (BOB): on the detection of weak magnetic fields in the two early B-type stars beta CMa and epsilon CMa
Fossati, L.; Castro, N.; Morel, Thierry ULg et al

in ArXiv e-prints (in press), 1411

Within the context of the "B fields in OB stars (BOB)" collaboration, we used the HARPSpol spectropolarimeter to observe the early B-type stars beta CMa (HD44743; B1 II/III) and epsilon CMa (HD52089; B1.5 ... [more ▼]

Within the context of the "B fields in OB stars (BOB)" collaboration, we used the HARPSpol spectropolarimeter to observe the early B-type stars beta CMa (HD44743; B1 II/III) and epsilon CMa (HD52089; B1.5 II). For both stars, we consistently detected the signature of a weak (<30 G in absolute value) longitudinal magnetic field. We determined the physical parameters of both stars and characterise their X-ray spectrum. For beta CMa, our mode identification analysis led to determining a rotation period of 13.6+/-1.2 days and of an inclination angle of the rotation axis of 57.6+/-1.7 degrees, with respect to the line of sight. On the basis of these measurements and assuming a dipolar field geometry, we derived a best fitting obliquity of ~22 degrees and a dipolar magnetic field strength (Bd) of ~100 G (60<Bd<230 G within 1 sigma), below what is typically found for other magnetic massive stars. For epsilon CMa we could only determine a lower limit on the dipolar magnetic field strength of 13 G. For this star, we determine that the rotation period ranges between 1.3 and 24 days. Both stars are expected to have a dynamical magnetosphere. We also conclude that both stars are most likely core hydrogen burning and that they have spent more than 2/3 of their main sequence lifetime. A histogram of the distribution of the dipolar magnetic field strength for the magnetic massive stars known to date does not show the magnetic field "desert" observed instead for intermediate-mass stars. The biases involved in the detection of (weak) magnetic fields in massive stars with the currently available instrumentation and techniques imply that weak fields might be more common than currently observed. Our results show that, if present, even relatively weak magnetic fields are detectable in massive stars and that more observational effort is probably still needed to properly access the magnetic field incidence. [less ▲]

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See detailThe B Fields in OB Stars (BOB) Survey
Morel, Thierry ULg; Castro, N.; Fossati, L. et al

in The Messenger (2014), 157

The B fields in OB stars (BOB) survey is an ESO Large Programme collecting spectropolarimetric observations for a large number of early-type stars in order to study the occurrence rate, properties, and ... [more ▼]

The B fields in OB stars (BOB) survey is an ESO Large Programme collecting spectropolarimetric observations for a large number of early-type stars in order to study the occurrence rate, properties, and ultimately the origin of magnetic fields in massive stars. A total of 98 objects was observed over 20 nights with FORS2 and HARPSpol to July 2014. Preliminary results indicate that the fraction of magnetic OB stars with an organised, detectable field is low. This conclusion, now independently reached by two different surveys, has profound implications for any theoretical model attempting to explain the field formation in these stars. We also discuss some important issues addressed by our observations (e.g., the lower bound of the field strength) and the discovery of some remarkable objects. [less ▲]

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See detailAbundance analysis, spectral variability, and search for the presence of a magnetic field in the typical PGa star HD 19400
Hubrig, S.; Castelli, F.; González, J. F. et al

in Monthly Notices of the Royal Astronomical Society (2014), 442

The aim of this study is to carry out an abundance determination, to search for spectral variability and for the presence of a weak magnetic field in the typical PGa star HD 19400. High-resolution, high ... [more ▼]

The aim of this study is to carry out an abundance determination, to search for spectral variability and for the presence of a weak magnetic field in the typical PGa star HD 19400. High-resolution, high signal-to-noise High Accuracy Radial-velocity Planet Searcher (HARPS) spectropolarimetric observations of HD 19400 were obtained at three different epochs in 2011 and 2013. For the first time, we present abundances of various elements determined using an ATLAS12 model, including the abundances of a number of elements not analysed by previous studies, such as Ne I, Ga II, and Xe II. Several lines of As II are also present in the spectra of HD 19400. To study the variability, we compared the behaviour of the line profiles of various elements. We report on the first detection of anomalous shapes of line profiles belonging to Mn and Hg, and the variability of the line profiles belonging to the elements Hg, P, Mn, Fe, and Ga. We suggest that the variability of the line profiles of these elements is caused by their non-uniform surface distribution, similar to the presence of chemical spots detected in HgMn stars. The search for the presence of a magnetic field was carried out using the moment technique and the Singular Value Decomposition (SVD) method. Our measurements of the magnetic field with the moment technique using 22 Mn II lines indicate the potential existence of a weak variable longitudinal magnetic field on the first epoch. The SVD method applied to the Mn II lines indicates <B[SUB]z[/SUB]> = -76 ± 25 G on the first epoch, and at the same epoch the SVD analysis of the observations using the Fe II lines shows <B[SUB]z[/SUB]> = -91 ± 35 G. The calculated false alarm probability values, 0.008 and 0.003, respectively, are above the value 10[SUP]-3[/SUP], indicating no detection. [less ▲]

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See detailCombining magnetic and seismic studies to constrain processes in massive stars
Neiner, C.; Degroote, P.; Coste, B. et al

in IAUS 302 - Magnetic Fields Throughout Stellar Evolution (2014, August)

The presence of pulsations influences the local parameters at the surface of massive stars and thus it modifies the Zeeman magnetic signatures. Therefore it makes the characterisation of a magnetic field ... [more ▼]

The presence of pulsations influences the local parameters at the surface of massive stars and thus it modifies the Zeeman magnetic signatures. Therefore it makes the characterisation of a magnetic field in pulsating stars more difficult and the characterisation of pulsations is thus required for the study of magnetic massive stars. Conversely, the presence of a magnetic field can inhibit differential rotation and mixing in massive stars and thus provides important constraints for seismic modelling based on pulsation studies. As a consequence, it is necessary to combine spectropolarimetric and seismic studies for all massive classical pulsators. Below we show examples of such combined studies and the interplay between physical processes. [less ▲]

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See detailExtensive study of HD 25558, a long-period double-lined binary with two SPB components
Sódor, Á.; De Cat, P.; Wright, D. J. et al

in Monthly Notices of the Royal Astronomical Society (2014), 438(4), 3535-3556

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 satellite light curves ... [more ▼]

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 satellite light curves revealed that this object is a double-lined spectroscopic binary with an orbital period of about 9 years. The observations do not allow the inference of an orbital solution. We determined the physical parameters of the components, and found that both lie within the SPB instability strip. Accordingly, both show line-profile variations due to stellar pulsations. Eleven independent frequencies were identified in the data. All the frequencies were attributed to one of the two components based on Pixel-by-pixel variability analysis of the line profiles. Spectroscopic and photometric mode identification was also performed for the frequencies of both stars. These results suggest that the inclination and rotation of the two components are rather different. The primary is a slow rotator with ~6 d period, seen at ~60 deg inclination, while the secondary rotates fast with ~1.2 d period, and is seen at ~20 inclination. Spectropolarimetric measurements revealed that the secondary component has a magnetic field with at least a few hundred Gauss strength, while no magnetic field can be detected in the primary. [less ▲]

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See detailSpectroscopic survey of Kepler stars: high-resolution observations of A- and F-type stars
Niemczura, E.; Smalley, B.; Murphy, S. et al

in IAU Symposium (2014, February 01)

Basic stellar parameters such as effective temperature, surface gravity, chemical composition, and projected rotational velocity, are important to classify stars and are crucial for successful ... [more ▼]

Basic stellar parameters such as effective temperature, surface gravity, chemical composition, and projected rotational velocity, are important to classify stars and are crucial for successful asteroseismic modelling. However, the Kepler space data do not provide such information. Therefore, ground-based spectral and multi-colour observations of Kepler asteroseismic targets are necessary to complement the space data. For this purpose, in coordination with the KASC ground-based observational Working Groups, high-resolution spectroscopic data for more than 500 B, A, F and G-type stars were collected. [less ▲]

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See detailExtensive spectroscopic and photometric study of HD 25558, a long orbital-period binary with two SPB components
Sódor, Á.; De Cat, P.; Wright, D. J. et al

in IAU Symposium (2014, February 01)

We carried out an extensive photometric and spectroscopic investigation of the SPB binary, HD 25558 (see Fig. 1 for the time and geographic distribution of the observations). The ~2000 spectra obtained at ... [more ▼]

We carried out an extensive photometric and spectroscopic investigation of the SPB binary, HD 25558 (see Fig. 1 for the time and geographic distribution of the observations). The ~2000 spectra obtained at 13 observatories during 5 observing seasons, the ground-based multi-colour light curves and the photometric data from the MOST satellite revealed that this object is a double-lined spectroscopic binary with a very long orbital period of about 9 years. We determined the physical parameters of the components, and have found that both lie within the SPB instability strip. Accordingly, both components show line-profile variations consistent with stellar pulsations. Altogether, 11 independent frequencies and one harmonic frequency were identified in the data. The observational data do not allow the inference of a reliable orbital solution, thus, disentangling cannot be performed on the spectra. Since the lines of the two components are never completely separated, the analysis is very complicated. Nevertheless, pixel-by-pixel variability analysis of the cross-correlated line profiles was successful, and we were able to attribute all the frequencies to the primary or secondary component. Spectroscopic and photometric mode-identification was also performed for several of these frequencies of both binary components. The spectroscopic mode-identification results suggest that the inclination and rotation of the two components are rather different. While the primary is a slow rotator with ~6 d rotation period, seen at ~60° inclination, the secondary rotates fast with ~1.2 d rotation period, and is seen at ~20° inclination. Our spectropolarimetric measurements revealed that the secondary component has a magnetic field with at least a few hundred Gauss strength, while no magnetic field was detected in the primary. The detailed analysis and results of this study will be published elsewhere. [less ▲]

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See detailA search for pulsations in the HgMn star HD 45975 with CoRoT photometry and ground-based spectroscopy
Morel, Thierry ULg; Briquet, Maryline ULg; Auvergne, M. et al

in Astronomy and Astrophysics (2014), 561

The existence of pulsations in HgMn stars is still being debated. To provide the first unambiguous observational detection of pulsations in this class of chemically peculiar objects, the bright star HD ... [more ▼]

The existence of pulsations in HgMn stars is still being debated. To provide the first unambiguous observational detection of pulsations in this class of chemically peculiar objects, the bright star HD 45975 was monitored for nearly two months by the CoRoT satellite. Independent analyses of the light curve provide evidence of monoperiodic variations with a frequency of 0.7572 d[SUP]-1[/SUP] and a peak-to-peak amplitude of ~2800 ppm. Multisite, ground-based spectroscopic observations overlapping the CoRoT observations show the star to be a long-period, single-lined binary. Furthermore, with the notable exception of mercury, they reveal the same periodicity as in photometry in the line moments of chemical species exhibiting strong overabundances (e.g., Mn and Y). In contrast, lines of other elements do not show significant variations. As found in otherHgMn stars, the pattern of variability consists in an absorption bump moving redwards across the line profiles. We argue that the photometric and spectroscopic changes are more consistent with an interpretation in terms of rotational modulation of spots at the stellar surface. In this framework, the existence of pulsations producing photometric variations above the ~50 ppm level is unlikely in HD 45975. This provides strong constraints on the excitation/damping of pulsation modes in this HgMn star. 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. This work is based on observations collected at La Silla and Paranal Observatories, ESO (Chile), with the HARPS and UVES spectrographs at the 3.6-m and very large telescopes, under programmes LP185.D-0056 and 287.D-5066. It is also based on observations made with the Mercator Telescope, operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. Based on observations obtained with the HERMES spectrograph, which is supported by the Fund for Scientific Research of Flanders (FWO), Belgium, the Research Council of K.U. Leuven, Belgium, the Fonds National de la Recherche Scientifique (FNRS), Belgium, the Royal Observatory of Belgium, the Observatoire de Genève, Switzerland, and the Thüringer Landessternwarte Tautenburg, Germany. [less ▲]

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See detailSpectropolarimetric Observations of Three Slowly Pulsating B Stars with the High Accuracy Radial Velocity Planet Searcher Spectrograph
Hubrig, S.; Ilyin, I.; Briquet, Maryline ULg et al

in Progress in Physics of the Sun and Stars: A New Era in Helio- and Asteroseismology (2013, December 01)

In our previous low-resolution spectropolarimetric observations with the Very Large Telescope (VLT), three slowly pulsating B-type (SPB) stars, HD 74195, HD 74560, and HD 85953, showed the presence of a ... [more ▼]

In our previous low-resolution spectropolarimetric observations with the Very Large Telescope (VLT), three slowly pulsating B-type (SPB) stars, HD 74195, HD 74560, and HD 85953, showed the presence of a weak magnetic field. The results of our new measurements, using high-resolution spectropolarimetric observations, formally showed significant detections above the 3σ level in the SPB stars HD 74195 and HD 85953. [less ▲]

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See detailPulsating B-type Stars in the Open Cluster NGC 884: Frequencies, Mode Identification, and Asteroseismology
Saesen, S.; Briquet, Maryline ULg; Aerts, C. et al

in Astronomical Journal (2013), 146

Recent progress in the seismic interpretation of field β Cep stars has resulted in improvements of the physical description in the stellar structure and evolution model computations of massive stars ... [more ▼]

Recent progress in the seismic interpretation of field β Cep stars has resulted in improvements of the physical description in the stellar structure and evolution model computations of massive stars. Further asteroseismic constraints can be obtained from studying ensembles of stars in a young open cluster, which all have similar age, distance, and chemical composition. We present an observational asteroseismology study based on the discovery of numerous multi-periodic and mono-periodic B stars in the open cluster NGC 884. We describe a thorough investigation of the pulsational properties of all B-type stars in the cluster. Overall, our detailed frequency analysis resulted in 115 detected frequencies in 65 stars. We found 36 mono-periodic, 16 bi-periodic, 10 tri-periodic, and 2 quadru-periodic stars and one star with nine independent frequencies. We also derived the amplitudes and phases of all detected frequencies in the U, B, V, and I filter, if available. We achieved unambiguous identifications of the mode degree for 12 of the detected frequencies in nine of the pulsators. Imposing the identified degrees and measured frequencies of the radial, dipole, and quadrupole modes of five pulsators led to a seismic cluster age estimate of log (age/yr) = 7.12-7.28 from a comparison with stellar models. Our study is a proof-of-concept for and illustrates the current status of ensemble asteroseismology of a young open cluster. [less ▲]

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See detailAn observational asteroseismic study of the pulsating B-stars in the open cluster NGC 884
Saesen, S.; Briquet, Maryline ULg; Aerts, C. et al

in IAU Symposium No. 301 (2013), "Precision Asteroseismology" (Wroclaw), W. Chaplin, J. Guzik, G. Handler & A. Pigulski (eds.) (2013, October 01)

Recent progress in the seismic interpretation of field {\beta} Cep stars has resulted in improvements of the physical description in the stellar structure and evolution model computations of massive stars ... [more ▼]

Recent progress in the seismic interpretation of field {\beta} Cep stars has resulted in improvements of the physical description in the stellar structure and evolution model computations of massive stars. Further asteroseismic constraints can be obtained from studying ensembles of stars in a young open cluster, which all have similar age, distance and chemical composition. We present an observational asteroseismic study based on the discovery of numerous multi-periodic and mono-periodic B-stars in the open cluster NGC 884. Our study illustrates the current status of ensemble asteroseismology of a young open cluster. [less ▲]

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See detailLow-amplitude rotational modulation rather than pulsations in the CoRoT B-type supergiant HD 46769
Aerts, C.; Simón-Díaz, S.; Catala, C. et al

in Astronomy and Astrophysics (2013), 557

<BR /> Aims: We aim to detect and interpret photometric and spectroscopic variability of the bright CoRoT B-type supergiant target HD 46769 (V = 5.79). We also attempt to detect a magnetic field in the ... [more ▼]

<BR /> Aims: We aim to detect and interpret photometric and spectroscopic variability of the bright CoRoT B-type supergiant target HD 46769 (V = 5.79). We also attempt to detect a magnetic field in the target. <BR /> Methods: We analyse a 23-day oversampled CoRoT light curve after detrending and spectroscopic follow-up data using standard Fourier analysis and phase dispersion minimization methods. We determine the fundamental parameters of the star, as well as its abundances from the most prominent spectral lines. We perform a Monte Carlo analysis of spectropolarimetric data to obtain an upper limit of the polar magnetic field, assuming a dipole field. <BR /> Results: In the CoRoT data, we detect a dominant period of 4.84 d with an amplitude of 87 ppm and some of its (sub-)multiples. Given the shape of the phase-folded light curve and the absence of binary motion, we interpret the dominant variability in terms of rotational modulation, with a rotation period of 9.69 d. Subtraction of the rotational modulation signal does not reveal any sign of pulsations. Our results are consistent with the absence of variability in the Hipparcos light curve. The spectroscopy leads to a projected rotational velocity of 72 ± 2 km s[SUP]-1[/SUP] and does not reveal periodic variability or the need to invoke macroturbulent line broadening. No signature of a magnetic field is detected in our data. A field stronger than ~500 G at the poles can be excluded, unless the possible non-detected field were more complex than dipolar. <BR /> Conclusions: The absence of pulsations and macroturbulence of this evolved B-type supergiant is placed into the context of instability computations and of observed variability of evolved B-type stars. Based on CoRoT space-based photometric data; the CoRoT space mission was developed and operated by the French space agency CNES, with the participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain. Based on observations collected at La Silla Observatory, ESO (Chile) with the HARPS spectrograph at the 3.6 m telescope, under programme LP185.D-0056. Based on observations obtained with the HERMES spectrograph attached to the 1.2 m Mercator telescope, which is supported by the Fund for Scientific Research of Flanders (FWO), Belgium, the Research Council of KU Leuven, Belgium, the Fonds National de la Recherche Scientific (FNRS), Belgium, the Royal Observatory of Belgium, the Observatoire de Genève, Switzerland, and the Thüringer Landessternwarte Tautenburg, Germany. Based on observations obtained with the Narval spectropolarimeter at the Observatoire du Pic du Midi (France), which is operated by the Institut National des Sciences de l'Univers (INSU). [less ▲]

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See detailDiscovery of a magnetic field in the CoRoT hybrid B-type pulsator HD 43317
Briquet, Maryline ULg; Neiner, C.; Leroy, B. et al

in Astronomy and Astrophysics (2013), 557

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 ... [more ▼]

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. 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). [less ▲]

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See detailMagnetic fields in beta Cep, SPB, and Be stars
Schoeller, M.; Hubrig, S.; Briquet, Maryline ULg et al

in Proceedings of the Conference: "Putting A Stars into Context: Evolution, Environment, and Related Stars" (2013, September 01)

Recent observational and theoretical results emphasize the potential significance of magnetic fields for structure, evolution, and environment of massive stars. Depending on their spectral and photometric ... [more ▼]

Recent observational and theoretical results emphasize the potential significance of magnetic fields for structure, evolution, and environment of massive stars. Depending on their spectral and photometric behavior, the upper main-sequence B-type stars are assigned to different groups, such as beta Cep stars and slowly pulsating B (SPB) stars, He-rich and He-deficient Bp stars, Be stars, BpSi stars, HgMn stars, or normal B-type stars. All these groups are characterized by different magnetic field geometry and strength, from fields below the detection limit of a few Gauss up to tens of kG. Our collaboration was the first to systematically study the magnetic fields in representative samples of different types of main-sequence B stars. In this article, we give an overview about what we have learned during the last years about magnetic fields in beta Cep, SPB, and Be stars. [less ▲]

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See detailAtmospheric parameters of 169 F-, G-, K- and M-type stars in the Kepler field
Molenda-Żakowicz, J.; Sousa, S. G.; Frasca, A. et al

in Monthly Notices of the Royal Astronomical Society (2013), 434

The asteroseismic and planetary studies, like all research related to stars, need precise and accurate stellar atmospheric parameters as input. We aim at deriving the effective temperature (T[SUB]eff[/SUB ... [more ▼]

The asteroseismic and planetary studies, like all research related to stars, need precise and accurate stellar atmospheric parameters as input. We aim at deriving the effective temperature (T[SUB]eff[/SUB]), the surface gravity (log g), the metallicity ([Fe/H]), the projected rotational velocity (v sin i) and the MK type for 169 F-, G-, K- and M-type Kepler targets which were observed spectroscopically from the ground with five different instruments. We use two different spectroscopic methods to analyse 189 high-resolution, high-signal-to-noise spectra acquired for the 169 stars. For 67 stars, the spectroscopic atmospheric parameters are derived for the first time. KIC 9693187 and 11179629 are discovered to be double-lined spectroscopic binary systems. The results obtained for those stars for which independent determinations of the atmospheric parameters are available in the literature are used for a comparative analysis. As a result, we show that for solar-type stars the accuracy of present determinations of atmospheric parameters is ±150 K in T[SUB]eff[/SUB], ±0.15 dex in [Fe/H] and ±0.3 dex in log g. Finally, we confirm that the curve-of-growth analysis and the method of spectral synthesis yield systematically different atmospheric parameters when they are applied to stars hotter than 6000 K. [less ▲]

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See detailTests of stellar interiors physics with classical pulsators
Briquet, Maryline ULg

Conference (2013, June 26)

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See detailTwo new SB2 binaries with main sequence B-type pulsators in the Kepler field
Pápics, P. I.; Tkachenko, A.; Aerts, C. et al

in Astronomy and Astrophysics (2013), 553(127),

Context: OB stars are important in the chemistry and evolution of the Universe, but the sample of targets well understood from an asteroseismological point of view is still too limited to provide feedback ... [more ▼]

Context: OB stars are important in the chemistry and evolution of the Universe, but the sample of targets well understood from an asteroseismological point of view is still too limited to provide feedback on the current evolutionary models. Our study extends this sample with two spectroscopic binary systems. AIMS. Our goal is to provide orbital solutions, fundamental parameters and abundances from disentangled high-resolution high signal-to-noise spectra, as well as to analyse and interpret the variations in the Kepler light curve of these carefully selected targets. This way we continue our efforts to map the instability strips of beta Cep and SPB stars using the combination of high-resolution ground-based spectroscopy and uninterrupted space-based photometry. Methods: We fit Keplerian orbits to radial velocities measured from selected absorption lines of high-resolution spectroscopy using synthetic composite spectra to obtain orbital solutions. We use revised masks to obtain optimal light curves from the original pixel-data from the Kepler satellite, which provided better long term stability compared to the pipeline processed light curves. We use various time-series analysis tools to explore and describe the nature of variations present in the light curve. Results: We find two eccentric double-lined spectroscopic binary systems containing a total of three main sequence B-type stars (and one F-type component) of which at least one in each system exhibits light variations. The light curve analysis (combined with spectroscopy) of the system of two B stars points towards the presence of tidally excited g modes in the primary component. We interpret the variations seen in the second system as classical g mode pulsations driven by the kappa mechanism in the B type primary, and explain the unexpected power in the p mode region as a result of nonlinear resonant mode excitation. [less ▲]

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