Seismic modelling of the<i>β</i> Cephei star HD 180642 (V1449 Aquilae)

Aerts, C.; Briquet, Maryline; Degroote, P.; Thoul, Anne; Hoolst, Tim Van

doi:10.1051/0004-6361/201117629

Cited by 38 publications

(50 citation statements)

References 44 publications

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“…The resulting periodogram from our SOFIN and FORS1 measurements displays three dominant peaks with the highest peak at f = 0.0720 d −1 corresponding to a period P = 13.893 d (Hubrig et al 2011d). This period was recently confirmed with seismic modeling based on CoRoT data and ground-based time-resolved spectroscopy by Aerts et al (2011), who also mention a somewhat high initial internal metallicity in their models, probably related to the presence of a magnetic field. The magnetic field geometry can likely be described by a centered dipole with a po- Fig.…”

Section: Magnetic Field Models For β Cephei and Spb Starssupporting

confidence: 52%

Magnetic field studies of massive main sequence stars

et al. 2011

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We report on the status of our spectropolarimetric observations of massive stars. During the last years, we have discovered magnetic fields in many objects of the upper main sequence, including Be stars, beta Cephei and Slowly Pulsating B stars, and a dozen O stars. Since the effects of those magnetic fields have been found to be substantial by recent models, we are looking into their impact on stellar rotation, pulsation, stellar winds, and chemical abundances. Accurate studies of the age, environment, and kinematic characteristics of the magnetic stars are also promising to give us new insight into the origin of the magnetic fields. Furthermore, longer time series of magnetic field measurements allow us to observe the temporal variability of the magnetic field and to deduce the stellar rotation period and the magnetic field geometry. Studies of the magnetic field in massive stars are indispensable to understand the conditions controlling the presence of those fields and their implications on the stellar physical parameters and evolution.Comment: 4 pages, 6 figures, to appear in Astronomische Nachrichten, Proceedings of the 7th Potsdam Thinkshop on "Magnetic Fields in Stars and Exoplanets

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Section: Magnetic Field Models For β Cephei and Spb Starssupporting

confidence: 52%

Magnetic field studies of massive main sequence stars

et al. 2011

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“…Results from asteroseismic modelling of massive main-sequence pulsators are broadly consistent with overshoot of a few tenths of a pressure scale height, but show a range of best-fitting parameters from consistent with zero (e.g. Aerts et al 2011) to more than 40 per cent of a pressure scale height (e.g. Briquet et al 2007); further corroboration is found in isochrone fitting of open clusters (Brott et al 2011, and references therein).…”

Section: Overshoot Excitationmentioning

confidence: 57%

The observational signatures of convectively excited gravity modes in main-sequence stars

Shiode¹,

Quataert²,

Cantiello³

et al. 2013

Monthly Notices of the Royal Astronomical Society

104

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We predict the flux and surface velocity perturbations produced by convectively excited gravity modes (g-modes) in main-sequence stars. Core convection in massive stars can excite g-modes to sufficient amplitudes to be detectable with high-precision photometry by Kepler and Convection, Rotation and planetary Transits (CoRoT), if the thickness of the convective overshoot region is 30 per cent of a pressure scale height. The g-modes manifest as excess photometric variability, with amplitudes of ∼10 μmag at frequencies 10 μHz (0.8 d −1 ) near the solar metallicity zero-age main sequence. The flux variations are largest for stars with M 5 M , but are potentially detectable down to M ∼ 2-3 M . During the main-sequence evolution, radiative damping decreases such that ever lower frequency modes reach the stellar surface and flux perturbations reach up to ∼100 μmag at the terminal-age main sequence. Using the same convective excitation model, we confirm previous predictions that solar gmodes produce surface velocity perturbations of 0.3 mm s −1 . This implies that stochastically excited g-modes are more easily detectable in the photometry of massive main-sequence stars than in the Sun.

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“…Given the fast rotation of a Be star, the observed frequency being twice as high as the highest one in the co-rotating frame of the star is less of a concern, as will be seen below. For the case of V1449 Aql this explanation is not unequivocally accepted; Aerts et al (2011) have suggested non-linear resonance arising from the interaction of a large number of other modes, while Degroote (2013) proposes that the dominant radial mode of V1449 Aql produces this signature through chaotic behavior. In any case, the similarity of the signature in the wavelet analysis remains striking, and the positive amplitude correlation between A 2 and A 3 could well be a clue towards the model of Aerts et al…”

Section: Outbursts and Pulsation Of Sthα166mentioning

confidence: 99%

Short-term variability and mass loss in Be stars

Rivinius

Baade

Carciofi

2016

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Context. Classical Be stars have been established as pulsating stars. Space-based photometric monitoring missions contributed significantly to that result. However, whether Be stars are just rapidly rotating SPB or β Cep stars, or whether they have to be understood differently, remains debated in the view of their highly complex power spectra. Aims. Kepler data of three known Be stars are re-visited to establish their pulsational nature and assess the properties of additional, non-pulsational variations. The three program stars turned out to be one inactive Be star, one active, continuously outbursting Be star, and one Be star transiting from a non-outbursting into an outbursting phase, thus forming an excellent sample to distill properties of Be stars in the various phases of their life-cycle. Methods. The Kepler data was first cleaned from any long-term variability with Lomb-Scargle based pre-whitening. Then a LombScargle analysis of the remaining short-term variations was compared to a wavelet analysis of the cleaned data. This offers a new view on the variability, as it enables us to see the temporal evolution of the variability and phase relations between supposed beating phenomena, which are typically not visualized in a Lomb-Scargle analysis. Results. The short-term photometric variability of Be stars must be disentangled into a stellar and a circumstellar part. The stellar part is on the whole not different from what is seen in non-Be stars. However, some of the observed phenomena might be to be due to resonant mode coupling, a mechanism not typically considered for B-type stars. Short-term circumstellar variability comes in the form of either a group of relatively well-defined, short-lived frequencies during outbursts, which are called Štefl frequencies, and broad bumps in the power spectra, indicating aperiodic variability on a time scale similar to typical low-order g-mode pulsation frequencies, rather than true periodicity. Conclusions. From a stellar pulsation perspective, Be stars are rapidly rotating SPB stars, that is they pulsate in low order g-modes, even if the rapid rotation can project the observed frequencies into the traditional high-order p-mode regime above about 4 c/d. However, when a circumstellar disk is present, Be star power spectra are complicated by both cyclic, or periodic, and aperiodic circumstellar phenomena, possibly even dominating the power spectrum.

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

Cited by 38 publications

References 44 publications

Magnetic field studies of massive main sequence stars

Magnetic field studies of massive main sequence stars

The observational signatures of convectively excited gravity modes in main-sequence stars

Short-term variability and mass loss in Be stars

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