References of "Godart, Mélanie"
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See detailCoRoT Observations of O Stars: Diverse Origins of Variability
Blomme, R.; Briquet, Maryline ULg; Degroote, P. et al

in Astronomical Society of the Pacific Conference Series (2013, January 01)

Six O-type stars were observed continuously by the CoRoT satellite during a 34.3-day run. The unprecedented quality of the data allows us to detect even low-amplitude stellar pulsations in some of these ... [more ▼]

Six O-type stars were observed continuously by the CoRoT satellite during a 34.3-day run. The unprecedented quality of the data allows us to detect even low-amplitude stellar pulsations in some of these stars (HD 46202 and the binaries HD 46149 and Plaskett's star). These cover both opacity-driven modes and solar-like stochastic oscillations, both of importance to the asteroseismological modeling of O stars. Additional effects can be seen in the CoRoT light curves, such as binarity and rotational modulation. Some of the hottest O-type stars (HD 46223, HD 46150 and HD 46966) are dominated by the presence of red-noise: we speculate that this is related to a sub-surface convection zone. [less ▲]

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See detailTheoretical Instability Domains of Massive Stars
Godart, Mélanie ULg; Dupret, Marc-Antoine ULg; Noels-Grötsch, Arlette ULg et al

in ASP Conference Proceeding, Vol. 462, 27 (2012, September 01)

Massive stars are characterized by a large radiation over gas pressure ratio. With increasing stellar initial mass, they suffer stronger stellar winds, and the induced mass-loss affects the evolution and ... [more ▼]

Massive stars are characterized by a large radiation over gas pressure ratio. With increasing stellar initial mass, they suffer stronger stellar winds, and the induced mass-loss affects the evolution and internal structure on the main sequence and on the post-main sequence. Recent ground-based observations and space missions have shown the presence of pulsations in massive stars, such as acoustic and gravity modes excited by the κ-mechanism and even solar-like oscillations. Strange modes could also be excited in the most massive stars (Aerts et al. 2010). We computed evolutionary tracks and non-adiabatic frequencies for initial masses ranging from 15 to 70 M[SUB]&sun;[/SUB] on the main sequence and on the post-main sequence taking mass loss into account and we discuss in this paper the results for 25 M[SUB]&sun;[/SUB] models. [less ▲]

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See detailUnveiling the internal structure and evolution of massive stars through their pulsation modes
Godart, Mélanie ULg

Doctoral thesis (2011)

Stars in the night sky are not as quiet as they seem. A human being wandering on Earth few billions years ago would have seen a different night sky, with different stars forming different constellations ... [more ▼]

Stars in the night sky are not as quiet as they seem. A human being wandering on Earth few billions years ago would have seen a different night sky, with different stars forming different constellations. Moving forward in time, he would have been the witness of stellar evolution as some stars would have suddenly shined while others disappeared forever. Hard to realize at a time scale of human life, stars are born, evolve, and die in a limited lifetime which can last only a few million years for the most massive to trillion years for the less massive. Fortunately, it is not necessary to wait that long to study the formation and evolution of stars. Stellar evolution can be studied on shorter time scales, on thousands of stars, at various evolutionary stages. This is of great importance as stars shape the Universe and produce the chemical elements at the origin of life. Probing the internal structure of stars is however very challenging due to the opacity barrier of their superficial layers. One way to get around this issue is to study and interpret stellar pulsations. As seismologists extract information about Earth interior trough the study of earthquakes, asteroseismologists can study the internal structure of stars by studying their oscillations. In this thesis, this technique is used to study the internal structure and evolution of massive stars which are at least eight times more massive than our Sun and which have a spectral type between O and B. The first part of this work is devoted to the determination of the $\kappa$-mechanism instability domains for massive stars. In order to extend the computations to the post-main sequence phase of evolution, we develop a numerical technique in which the non-adiabatic computations for the stellar core are made, independently than for the envelope, within the quasi-adiabatic and the asymptotic treatment. In a second step, we investigate the pulsations modes in O main sequence stars and in B post-main sequence stars. The presence of g-modes in post-main sequence stars is closely related to the internal structure of the star and we study the effects of several physical factors on the occurrence of these modes. Finally, the last part of this work is dedicated to the characterization of strange mode pulsations. In particular, we focus on strange modes having an adiabatic counterpart, which are trapped into a superficial cavity. The effect of the model atmosphere on the excitation is investigated in addition to the characterization of their eigenfunctions. [less ▲]

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See detailVariability in the CoRoT photometry of three hot O-type stars. HD 46223, HD 46150, and HD 46966
Blomme, R.; Mahy, Laurent ULg; Catala, C. et al

in Astronomy and Astrophysics (2011), 533

Context. The detection of pulsational frequencies in stellar photometry is required as input for asteroseismological modelling. The second short run (SRa02) of the CoRoT mission has provided photometric ... [more ▼]

Context. The detection of pulsational frequencies in stellar photometry is required as input for asteroseismological modelling. The second short run (SRa02) of the CoRoT mission has provided photometric data of unprecedented quality and time-coverage for a number of O-type stars. <BR /> Aims: We analyse the CoRoT data corresponding to three hot O-type stars, describing the properties of their light curves and search for pulsational frequencies, which we then compare to theoretical model predictions. <BR /> Methods: We determine the amplitude spectrum of the data, using the Lomb-Scargle and a multifrequency HMM-like technique. Frequencies are extracted by prewhitening, and their significance is evaluated under the assumption that the light curve is dominated by red noise. We search for harmonics, linear combinations, and regular spacings among these frequencies. We use simulations with the same time sampling as the data as a powerful tool to judge the significance of our results. From the theoretical point of view, we use the MAD non-adiabatic pulsation code to determine the expected frequencies of excited modes. <BR /> Results: A substantial number of frequencies is listed, but none can be convincingly identified as being connected to pulsations. The amplitude spectrum is dominated by red noise. Theoretical modelling shows that all three O-type stars can have excited modes, but the relation between the theoretical frequencies and the observed spectrum is not obvious. <BR /> Conclusions: The dominant red noise component in the hot O-type stars studied here clearly points to a different origin than the pulsations seen in cooler O stars. The physical cause of this red noise is unclear, but we speculate on the possibility of sub-surface convection, granulation, or stellar wind inhomogeneities being responsible. 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.Tables 2-4 are available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/533/A4">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/533/A4</A> [less ▲]

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See detailSeismic modelling of OB stars
Dupret, Marc-Antoine ULg; Godart, Mélanie ULg; Belkacem, Kevin ULg et al

in Proceedings of the International Astronomical Union (2011), 272

A review of the ability of asteroseismology to probe the internal physics of OB stars is presented. The main constraints that can be obtained from the frequency spectrum in p- and g-modes pulsators are ... [more ▼]

A review of the ability of asteroseismology to probe the internal physics of OB stars is presented. The main constraints that can be obtained from the frequency spectrum in p- and g-modes pulsators are discussed. Next, we consider energetic aspects of the pulsations in OB stars and show how such study also allows to constrain their internal physics. The cases of p-mixed modes (β Cep stars), g-modes (SPB stars), strange modes and stochastically excited modes are considered. [less ▲]

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See detailPulsations in massive stars: effect of the atmosphere on the strange mode pulsations
Godart, Mélanie ULg; Dupret, Marc-Antoine ULg; Noels-Grötsch, Arlette ULg et al

in Proceedings of the International Astronomical Union (2011), 272

Recent space observations with CoRoT and ground-based spectroscopy have shown the presence of different types of pulsations in OB stars. These oscillations could be due to acoustic and gravity modes ... [more ▼]

Recent space observations with CoRoT and ground-based spectroscopy have shown the presence of different types of pulsations in OB stars. These oscillations could be due to acoustic and gravity modes, solar-like oscillations or even other pulsations of large growth rates. We present a first attempt at interpreting the latter as strange modes. [less ▲]

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See detailTheoretical instability domains in the upper part of the HR diagram
Godart, Mélanie ULg

Conference (2011, March)

Massive stars are characterized by a large radiation over gaz pressure ratio and a large temperature over density ratio. With increasing stellar initial mass, they suffer stronger stellar winds which ... [more ▼]

Massive stars are characterized by a large radiation over gaz pressure ratio and a large temperature over density ratio. With increasing stellar initial mass, they suffer stronger stellar winds which plays an important role in the chemical enrichment of the galaxies. The induced mass loss affects also the evolution and internal structure of massive stars on the main sequence (MS) and on the post-main sequence phase (post-MS). Recent ground-based observations and space missions have shown the presence of pulsations in massive stars, such as accouctic and gravity modes excited by the $\kappa$-mechanism and even solar-like oscillations. Strange modes could also found to be excited in the most massive stars. $\kappa$-mechanism instability domains are presented for the upper HR diagram (up to $70$M$_{odot}$) on the MS and on the post-MS. We compute evolutionary tracks and non-adiabatic frequencies for different input parameters such as the metallicity, the mass loss rate and the overshooting parameter. [less ▲]

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See detailThe multiplicity of O-type stars in NGC 2244
Mahy, Laurent ULg; Rauw, Grégor ULg; Martins, F. et al

in Bulletin de la Societe Royale des Sciences de Liege (2011), 80

The investigation of the multiplicity of massive stars is crucial to determine a robust binary fraction but also for understanding the physical properties of these objects. In this contribution, we will ... [more ▼]

The investigation of the multiplicity of massive stars is crucial to determine a robust binary fraction but also for understanding the physical properties of these objects. In this contribution, we will present the main results from our long-term spectroscopic survey devoted to the young open cluster NGC 2244. We discuss the spectral classification, the projected rotational velocity (v sin{i}) and the multiplicity of O-stars. The stellar and wind parameters of each star, obtained using the CMFGEN atmosphere code, help us to better constrain the individual properties of these objects. Several of these stars were observed by the CoRoT satellite (SRa02) in the Asteroseismology channel. This intensive monitoring and the unprecedented quality of the light curves allow us to shed a new light on these objects. [less ▲]

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See detailPlaskett's star: analysis of the CoRoT photometric data
Mahy, Laurent ULg; Gosset, Eric ULg; Baudin, F. et al

in Astronomy and Astrophysics (2011), 525

Context. The second short run (SRa02) of the CoRoT space mission for asteroseismology was partly devoted to stars belonging to the Mon OB2 association. An intense monitoring has been performed on Plaskett ... [more ▼]

Context. The second short run (SRa02) of the CoRoT space mission for asteroseismology was partly devoted to stars belonging to the Mon OB2 association. An intense monitoring has been performed on Plaskett's star (HD 47129) and the unprecedented quality of the light curve allows us to shed new light on this very massive, non-eclipsing binary system. <BR /> Aims: We particularly aimed at detecting periodic variability that might be associated with pulsations or interactions between both components. We also searched for variations related to the orbital cycle that could help to constrain the inclination and the morphology of the binary system. <BR /> Methods: We applied an iterative Fourier-based prewhitening and a multiperiodic fitting procedure to analyse the time series and extract the frequencies of variations from the CoRoT light curve. We describe the noise properties to tentatively define an appropriate significance criterion and, in consequence, to only point out the peaks at a certain significance level. We also detect the variations related to the orbital motion and study them with the NIGHTFALL programme. <BR /> Results: The periodogram computed from Plaskett's star CoRoT light curve mainly exhibits a majority of peaks at low frequencies. Among these peaks, we highlight a list of 43 values, notably including two different sets of harmonic frequencies whose fundamental peaks are located at about 0.07 and 0.82 d[SUP]-1[/SUP]. The former represents the orbital frequency of the binary system, whilst the latter could probably be associated with non-radial pulsations. The study of the 0.07 d[SUP]-1[/SUP] variations reveals a hot spot most probably situated on the primary star and facing the secondary. <BR /> Conclusions: The investigation of this unique dataset constitutes a further step in the understanding of Plaskett's star. These results provide a first basis for future seismic modelling and put forward the probable existence of non-radial pulsations in Plaskett's star. Moreover, the fit of the orbital variations confirms the problem of the distance of this system which was already mentioned in previous works. A hot region between both components renders the determination of the inclination ambiguous. 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.Table 2 is only available in electronic form at <A href="http://www.aanda.org">http://www.aanda.org</A> [less ▲]

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See detailOvershooting and semiconvection: structural changes and asteroseismic signatures
Noels-Grötsch, Arlette ULg; Montalban Iglesias, Josefa ULg; Miglio, Andrea ULg et al

in Astrophysics & Space Science (2010), 328

Overshooting and semiconvection are two poorly known mechanisms which affect the extent and the efficiency of chemical mixing outside classical convection zones in stars. We discuss the uncertainties and ... [more ▼]

Overshooting and semiconvection are two poorly known mechanisms which affect the extent and the efficiency of chemical mixing outside classical convection zones in stars. We discuss the uncertainties and the inferences of those processes in main sequence stars burning hydrogen in a convective core. We then focus on the asteroseismic signatures of partially or fully mixed zones surrounding the convective core, through the detailed shape of the induced chemical composition profile. We emphasize the potential power of asteroseismology to determine the internal structure of stars and thus to help us understand the physical processes at work inside the stars. [less ▲]

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See detailPulsations in O and B stars
Godart, Mélanie ULg

Conference (2010, June)

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See detailPeriodic mass-loss episodes due to an oscillation mode with variable amplitude in the hot supergiant HD 50064
Aerts, C.; Lefever, K.; Baglin, A. et al

in Astronomy and Astrophysics (2010), 513

<BR /> Aims: We aim to interpret the photometric and spectroscopic variability of the luminous blue variable supergiant HD 50064 (V = 8.21). <BR /> Methods: CoRoT space photometry and follow-up high ... [more ▼]

<BR /> Aims: We aim to interpret the photometric and spectroscopic variability of the luminous blue variable supergiant HD 50064 (V = 8.21). <BR /> Methods: CoRoT space photometry and follow-up high-resolution spectroscopy with a time base of 137 d and 169 d, respectively, was gathered, analysed, and interpreted using standard time series analysis and light curve modelling methods, as well as spectral line diagnostics. <BR /> Results: The space photometry reveals one period of 37 d, which undergoes a sudden amplitude change with a factor 1.6. The pulsation period is confirmed in the spectroscopy, which additionally reveals metal line radial velocity values differing by 30 km s[SUP]-1[/SUP] depending on the spectral line and on the epoch. We estimate T[SUB]eff[/SUB] 13 500 K, log g 1.5 from the equivalent width of Si lines. The Balmer lines reveal that the star undergoes episodes of changing mass loss on a time scale similar to the changes in the photometric and spectroscopic variability, with an average value of log dot{M} â -5 (in M_ȯ yr[SUP]-1[/SUP]). We tentatively interpret the 37 d period as the result of a strange mode oscillation. Based on high-resolution spectroscopy assembled with the CORALIE spectrograph attached to the 1.2 m Euler telescope at La Silla, Chile and on CoRoT space-based photometry. The CoRoT space mission was developed and is operated by the French space agency CNES, with the participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain.Postdoctoral Fellow of the Fund for Scientific Research of Flanders (FWO), Belgium. [less ▲]

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See detailCollective pulsational velocity broadening due to gravity modes as a physical explanation for macroturbulence in hot massive stars
Aerts, C.; Puls, J.; Godart, Mélanie ULg et al

in Astronomy and Astrophysics (2009), 508

Aims. We aimed at finding a physical explanation for the occurrence of macroturbulence in the atmospheres of hot massive stars, a phenomenon found in observations for more than a decade but that remains ... [more ▼]

Aims. We aimed at finding a physical explanation for the occurrence of macroturbulence in the atmospheres of hot massive stars, a phenomenon found in observations for more than a decade but that remains unexplained.<BR /> Methods: We computed time series of line profiles for evolved massive stars broadened by rotation and by hundreds of low-amplitude nonradial gravity-mode pulsations which are predicted to be excited for evolved massive stars.<BR /> Results: In general, line profiles based on macrotubulent broadening can mimic those subject to pulsational broadening. In several cases, though, good fits require macroturbulent velocities that pass the speed of sound for realistic pulsation amplitudes. Moreover, we find that the rotation velocity can be seriously underestimated by using a simple parameter description for macroturbulence rather than an appropriate pulsational model description to fit the line profiles.<BR /> Conclusions: We conclude that macroturbulence is a likely signature of the collective effect of pulsations. We provide line diagnostics and their typical values to decide whether or not pulsational broadening is present in observed line profiles, as well as a procedure to avoid an inaccurate estimation of the rotation velocity. [less ▲]

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See detailTheoretical amplitudes and lifetimes of non-radial solar-like oscillations in red giants
Dupret, Marc-Antoine ULg; Belkacem, Kevin ULg; Samadi, Réza et al

in Astronomy and Astrophysics (2009), 506

Context: Solar-like oscillations have been observed in numerous red giants from ground and from space. An important question arises: could we expect to detect non-radial modes probing the internal ... [more ▼]

Context: Solar-like oscillations have been observed in numerous red giants from ground and from space. An important question arises: could we expect to detect non-radial modes probing the internal structure of these stars? <BR />Aims: We investigate under what physical circumstances non-radial modes could be observable in red giants; what would be their amplitudes, lifetimes and heights in the power spectrum (PS)? <BR />Methods: Using a non-radial non-adiabatic pulsation code including a non-local time-dependent treatment of convection, we compute the theoretical lifetimes of radial and non-radial modes in several red giant models. Next, using a stochastic excitation model, we compute the amplitudes of these modes and their heights in the PS. <BR />Results: Distinct cases appear. Case A corresponds to subgiants and stars at the bottom of the ascending giant branch. Our results show that the lifetimes of the modes are mainly proportional to the inertia I, which is modulated by the mode trapping. The predicted amplitudes are lower for non-radial modes. But the height of the peaks in the PS are of the same order for radial and non-radial modes as long as they can be resolved. The resulting frequency spectrum is complex. Case B corresponds to intermediate models in the red giant branch. In these models, the radiative damping becomes high enough to destroy the non-radial modes trapped in the core. Hence, only modes trapped in the envelope have significant heights in the PS and could be observed. The resulting frequency spectrum of detectable modes is regular for â =0 and 2, but a little more complex for â =1 modes because of less efficient trapping. Case C corresponds to models of even higher luminosity. In these models the radiative damping of non-radial modes is even larger than in the previous case and only radial and non-radial modes completely trapped in the envelope could be observed. The frequency pattern is very regular for these stars. The comparison between the predictions for radial and non-radial modes is very different if we consider the heights in the PS instead of the amplitudes. This is important as the heights (not the amplitudes) are used as detection criterion. CIFIST Marie Curie Excellence Team. [less ▲]

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See detailUnveiling the internal structure of massive supergiants: HD 163899
Godart, Mélanie ULg; Dupret, Marc-Antoine ULg; Noels-Grötsch, Arlette ULg

in Communications in Asteroseismology (2009), 158

Supergiant massive stars are post-main sequence stars. During the H shell burning phase of evolution, they present a radiative core in which a strong damping prevents the pulsation modes from being ... [more ▼]

Supergiant massive stars are post-main sequence stars. During the H shell burning phase of evolution, they present a radiative core in which a strong damping prevents the pulsation modes from being excited. However Saio et al. (2006) have recently highlighted p and g pulsation modes in a post-main sequence star (HD 163899) observed by MOST. They suggest that the presence of an intermediate convective region (ICZ) at the top of the radiative core allows a partial or total reflexion of the mode. Through some numerical results achieved with CLES (Scuflaire et al. 2008) and MAD (Dupret et al. 2003) codes, we show that this scenario depends on the evolution stage of the star and on the considered mass loss rate and overshooting parameter. [less ▲]

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See detailLedoux's convection criterion in evolution and asteroseismology of massive stars
Lebreton, Yves; Montalban Iglesias, Josefa ULg; Godart, Mélanie ULg et al

in Communications in Asteroseismology (2009), 158

Saio et al. (2006) have shown that the presence of an intermediate convective zone (ICZ) in post-main sequence models could prevent the propagation of g-modes in the radiative interior and hence avoid the ... [more ▼]

Saio et al. (2006) have shown that the presence of an intermediate convective zone (ICZ) in post-main sequence models could prevent the propagation of g-modes in the radiative interior and hence avoid the corresponding radiative damping. The development of such a convective region highly depends on the structure of the star in the mu-gradient region surrounding the convective core during the main sequence phase. In particular,the development of this ICZ depends on physical processes such as mass loss, overshooting (Chiosi & Maeder 1986, Chiosi et al. 1992, see also Godart et al., 2009) and convective instability criterion (Schwarzschild's or Ledoux's criteria). In this paper we study the consequences of adopting the Ledoux's criterion on the evolution of the convective regions in massive stars (15 and 20 M_{o}), and on the pulsation spectrum of these new B-type variables (also called SPBsg). [less ▲]

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See detailCan mass loss and overshooting prevent the excitation of g-modes in blue supergiants?
Godart, Mélanie ULg; Noels-Grötsch, Arlette ULg; Dupret, Marc-Antoine ULg et al

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

Thanks to their past history on the main-sequence phase, supergiant massive stars develop a convective shell around the helium core. This intermediate convective zone (ICZ) plays an essential role in ... [more ▼]

Thanks to their past history on the main-sequence phase, supergiant massive stars develop a convective shell around the helium core. This intermediate convective zone (ICZ) plays an essential role in governing which g-modes are excited. Indeed, a strong radiative damping occurs in the high-density radiative core but the ICZ acts as a barrier preventing the propagation of some g-modes into the core. These g-modes can thus be excited in supergiant stars by the kappa-mechanism in the superficial layers due to the opacity bump of iron, at logT = 5.2. However, massive stars are submitted to various complex phenomena such as rotation, magnetic fields, semiconvection, mass loss, overshooting. Each of these phenomena exerts a significant effect on the evolution and some of them could prevent the onset of the convective zone. We develop a numerical method which allows us to select the reflected, thus the potentially excited, modes only. We study different cases in order to show that mass loss and overshooting, in a large enough amount, reduce the extent of the ICZ and are unfavourable to the excitation of g-modes. [less ▲]

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See detailOn the origin of macroturbulence in hot stars
Aerts, C.; Puls, J.; Godart, Mélanie ULg et al

in Communications in Asteroseismology (2009), 158

Since the use of high-resolution high signal-to-noise spectroscopy in the study of massive stars, it became clear that an ad-hoc velocity field at the stellar surface, termed macroturbulence, is needed to ... [more ▼]

Since the use of high-resolution high signal-to-noise spectroscopy in the study of massive stars, it became clear that an ad-hoc velocity field at the stellar surface, termed macroturbulence, is needed to bring the observed shape of spectral lines into agreement with observations. We seek a physical explanation of this unknown broadening mechanism. We interprete the missing line broadening in terms of collective pulsational velocity broadening due to non-radial gravity-mode oscillations. We also point out that the rotational velocity can be seriously underestimated whenever the line profiles are fitted assuming a Gaussian macroturbulent velocity rather than an appropriate pulsational velocity expression. [less ▲]

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See detailSignature of main sequence internal structure in post-main sequence stars
Dupret, Marc-Antoine ULg; Godart, Mélanie ULg; Noels-Grötsch, Arlette ULg et al

in Communications in Asteroseismology (2009), 158

Post Main Sequence (post MS) stars keep a trace of their past main sequence history. Typically, the presence or not of an Intermediate Convective Zone (ICZ) above the H-burning shell of massive stars ... [more ▼]

Post Main Sequence (post MS) stars keep a trace of their past main sequence history. Typically, the presence or not of an Intermediate Convective Zone (ICZ) above the H-burning shell of massive stars critically depends on the details of the Main Sequence (MS) phase modeling (convection criterion, mass loss,~...). We show here how the excitation of g-modes in blue supergiant stars is closely related to this ICZ, allowing to constrain different associated physical processes. [less ▲]

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See detailIs HD 163899 really a supergiant star?
Godart, Mélanie ULg; Dupret, Marc-Antoine ULg; Noels-Grötsch, Arlette ULg

in Communications in Asteroseismology (2008), 157

According to its spectral type B2 Ib/I I (Klare & Neckel 1977; Schmidt & Carruthers 1996), HD163899 is a supergiant star. The star presents p and g-mode pulsations (Saio et al. 2006). In such a post-main ... [more ▼]

According to its spectral type B2 Ib/I I (Klare & Neckel 1977; Schmidt & Carruthers 1996), HD163899 is a supergiant star. The star presents p and g-mode pulsations (Saio et al. 2006). In such a post-main sequence (post MS) star, the helium core is radiative with a very large Brunt-Väisälä frequency which produces a strong damping. The presence of excited g-modes is however possible thanks to an intermediate convective zone (ICZ) which prevents some g-modes from entering the radiative damping core (Saio et al. 2006). We have investigated an alternative solution. We show that MS evolutionary tracks could cross the error box of HD 163899 if a sufficiently large amount of overshooting is taken into account. However, in that case, the spectrum of unstable modes is different from the spectrum of a supergiant star since the Brunt-Väisälä frequency is much smaller. [less ▲]

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