The pulsations of the B5IVe star HD 181231 observed  with CoRoT and ground-based spectroscopy

Neiner, C.; Gutiérrez‐Soto, J.; Baudin, F.; Batz, B. de; Frémat, Y.; Huat, Anne-Laure; Floquet, M.; Hubert, A. M.; Leroy, B.; Diago, P. D.; Poretti, E.; Carrier, F.; Rainer, M.; Catala, C.; Thizy, O.; Buil, C.; Ribeiro, José Pancrácio; Andrade, L.; Emílio, M.; Lara, F. Espinosa; Fabregat, J.; Janot-Pacheco, E.; Martayan, Christophe; Semaan, T.; Suso, J.; Baglin, A.; Michel, E.; Samadi, R.

doi:10.1051/0004-6361/200911971

Cited by 41 publications

(43 citation statements)

References 27 publications

(26 reference statements)

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“…They have been observed with the CoRoT photometric satellite (for a description of CoRoT, see Baglin et al 2006Baglin et al , 2009 during about five consecutive months and 27 consecutive days, respectively. A&A 539, A90 (2012) An analysis of their CoRoT light curves showed that several independent periods of variations are present in these stars, which we interpreted in terms of pulsation g-modes (Neiner et al 2009;Gutiérrez-Soto et al 2009). Late Be stars indeed exhibit pulsations of g-modes similar to those of slowly pulsating B (SPB) stars.…”

Section: Introductionmentioning

confidence: 78%

“…Assuming Ω Ωc = 0.9, as determined by Neiner et al (2009) andGutiérrez-Soto et al (2009). are summarized in Table 1. See also Table 3 of Neiner et al (2009).…”

Section: Hd 181231mentioning

confidence: 99%

“…In addition, the amplitude of variations detected in HD 175869 is lower than that in HD 181231, as expected because of its later spectral type. Because the pulsations of HD 181231 and HD 175869 have been characterized with great precision thanks to CoRoT by Neiner et al (2009) and Gutiérrez-Soto et al (2009) and their fundamental parameters were determined from spectroscopy by the same authors, these late Be stars are very good candidates for seismic modelling. Furthermore, because we know that these Be stars rotate with an angular velocity close to their break-up velocity, they are relevant targets for probing and obtaining tight constraints on the physical processes related to their internal rotation.…”

Section: Introductionmentioning

confidence: 99%

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Seismic modelling of the late Be stars HD 181231 and HD 175869 observed with CoRoT: a laboratory for mixing processes

Neiner

Mathis

Saio

et al. 2012

A&A

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Context. HD 181231 and HD 175869 are two late rapidly rotating Be stars, which have been observed using high-precision photometry with the CoRoT satellite during about five consecutive months and 27 consecutive days, respectively. An analysis of their light curves, by Neiner and collaborators and Gutiérrez-Soto and collaborators respectively, showed that several independent pulsation g-modes are present in these stars. Fundamental parameters have also been determined by these authors using spectroscopy. Aims. We aim to model these results to infer seismic properties of HD 181231 and HD 175869, and constrain internal transport processes of rapidly rotating massive stars. Methods. We used an adiabatic (NRO) and a non-adiabatic (Tohoku) oscillation code that accounts for the combined action of Coriolis and centrifugal accelerations on stellar pulsations as needed for rapid rotator modelling. We coupled these codes with a 2D (ROTORC) stellar structure model to take the rotational deformation of the star into account. The action of transport processes was parametrised with the mixing parameter α ov , which represents the "non-standard" extension of the convective core, and determined by matching observed pulsation frequencies assuming a single star evolution scenario. In a second step, we used (Geneva) evolution models to evaluate the contribution of the secular rotational transport and mixing processes in the radiative envelope. A Monte Carlo analysis of spectropolarimetric data was also performed to examine the role of a potential fossil magnetic field. Finally, based on state-of-the-art modelling of penetrative convection and internal waves, we unravelled their respective contribution to the needed "non-standard" mixing.Results. We find that extra mixing of α ov = 0.3−0.35H p is needed in HD 181231 and HD 175869 to match the observed frequencies with those of prograde sectoral g-modes. We also detect the possible presence of r-modes. We investigated the respective contributions of several transport processes to this mixing: the hydrodynamical processes in particular the meridional circulation and shear-induced turbulence caused by the radiative envelope differential rotation, the possible magnetic field, the penetrative convection at the top of the convective core, and the transport by internal waves. Conclusions. We showed that the extension of the convective core needed to match observations and models may be explained by mixing induced by the penetrative movements at the bottom of the radiative envelope and by the secular hydrodynamical transport processes induced by the rotation in the envelope. We showed how asteroseismology opens a new door to probe transport processes in stellar interiors.

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Section: Introductionmentioning

confidence: 78%

“…Assuming Ω Ωc = 0.9, as determined by Neiner et al (2009) andGutiérrez-Soto et al (2009). are summarized in Table 1. See also Table 3 of Neiner et al (2009).…”

Section: Hd 181231mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Seismic modelling of the late Be stars HD 181231 and HD 175869 observed with CoRoT: a laboratory for mixing processes

Neiner

Mathis

Saio

et al. 2012

A&A

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“…A remarkable finding is the outburst signal detected in the B0.5IVe star HD 49330 (Huat et al 2009), a phenomenon that has not been observed to occur in any of the other observed Be stars, which are of later spectral type. Theoretical work is needed to understand and interpret the observed frequency patterns in the Be pulsators (Neiner et al 2009;Diago et al 2009;Gutiérrez-Soto et al 2009). Progress is hampered by the mathematical complexity of describing the oscillations in these flattened stars, induced by their rapid rotation, often close to their critical velocity.…”

Section: Introductionmentioning

confidence: 99%

Seismic modelling of theβ Cephei star HD 180642 (V1449 Aquilae)

Aerts

Briquet

Degroote

et al. 2011

A&A

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Context. We present modelling of the β Cep star HD 180642 based on its observational properties deduced from CoRoT and groundbased photometry as well as from time-resolved spectroscopy. Aims. We investigate whether present-day state-of-the-art models are able to explain the full seismic behaviour of this star, which has extended observational constraints for this type of pulsator. Methods. We constructed a dedicated database of stellar models and their oscillation modes tuned to fit the dominant radial mode frequency of HD 180642, by means of varying the hydrogen content, metallicity, mass, age, and core overshooting parameter. We compared the seismic properties of these models with those observed. Results. We find models that are able to explain the numerous observed oscillation properties of the star, for a narrow range in mass of 11.4-11.8 M and no or very mild overshooting (with up to 0.05 local pressure scale heights), except for an excitation problem of the = 3, p 1 mode. We deduce a rotation period of about 13 d, which is fully compatible with recent magnetic field measurements. The seismic models do not support the earlier claim of solar-like oscillations in the star. We instead ascribe the power excess at high frequency to non-linear resonant mode coupling between the high-amplitude radial fundamental mode and several of the low-order pressure modes. We report a discrepancy between the seismic and spectroscopic gravity at the 2.5σ level.

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“…The current theoretical models have difficulties in describing the pulsational characteristics of Be stars, due to the high rotational velocity of these objects. A brief description of the current knowledge of the pulsational behavior of Be stars can be found in Neiner et al (2009) and Emilio et al (in prep. ).…”

Section: Introductionmentioning

confidence: 99%

Pulsations in the late-type Be star HD 50 209 detected by CoRoT

Diago¹,

Gutiérrez‐Soto

Auvergne

et al. 2009

A&A

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Context. The presence of pulsations in late-type Be stars is still a matter of controversy. It constitutes an important issue to establish the relationship between non-radial pulsations and the mass-loss mechanism in Be stars. Aims. To contribute to this discussion, we analyse the photometric time series of the B8IVe star HD 50 209 observed by the CoRoT mission in the seismology field. Methods. We use standard Fourier techniques and linear and non-linear least squares fitting methods to analyse the CoRoT light curve. In addition, we applied detailed modelling of high-resolution spectra to obtain the fundamental physical parameters of the star. Results. We have found four frequencies which correspond to gravity modes with azimuthal order m = 0, −1, −2, −3 with the same pulsational frequency in the co-rotating frame. We also found a rotational period with a frequency of 0.679 cd −1 (7.754 μHz). Conclusions. HD 50 209 is a pulsating Be star as expected from its position in the HR diagram, close to the SPB instability strip.

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The pulsations of the B5IVe star HD 181231 observed with CoRoT and ground-based spectroscopy

Cited by 41 publications

References 27 publications

Seismic modelling of the late Be stars HD 181231 and HD 175869 observed with CoRoT: a laboratory for mixing processes

Seismic modelling of the late Be stars HD 181231 and HD 175869 observed with CoRoT: a laboratory for mixing processes

Seismic modelling of theβ Cephei star HD 180642 (V1449 Aquilae)

Pulsations in the late-type Be star HD 50 209 detected by CoRoT

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