MOSTDetects SPBe Pulsations in HD 127756 and HD 217543: Asteroseismic Rotation Rates Independent ofv sin i

Cameron, Chris; Saio, Hideyuki; Kuschnig, R.; Walker, G. A. H.; Matthews, J. M.; Guenther, D. B.; Moffat, A. F. J.; Ruciński, S. M.; Sasselov, Dimitar; Weiß, W. W.

doi:10.1086/590369

Cited by 46 publications

(50 citation statements)

References 38 publications

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“…This is excellent news, as it solves the problem of mode identification ! Such an effect was indeed observed in several SPBe stars (Cameron et al 2008).…”

Section: Energetic Aspects In Fast Rotatorssupporting

confidence: 64%

Seismic modelling of OB stars

Dupret¹,

Godart²,

Belkacem³

et al. 2010

Proc. IAU

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Abstract.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 pand 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.

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“…This is excellent news, as it solves the problem of mode identification ! Such an effect was indeed observed in several SPBe stars (Cameron et al 2008).…”

Section: Energetic Aspects In Fast Rotatorssupporting

confidence: 64%

Seismic modelling of OB stars

Dupret¹,

Godart²,

Belkacem³

et al. 2010

Proc. IAU

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“…They are typically interpreted in terms of a dense population of loworder g-modes (Walker et al 2005;Dziembowski et al 2007;Cameron et al 2008), though Balona (2009) has suggested a rotational or circumstellar interpretation. Here it is argued that they are indeed circumstellar, though not necessarily connected to rotation, just due to aperiodic variability residing in the circumstellar environment, that is the gaseous disk (see Paper I).…”

Section: Broad Bumps In the Power Spectramentioning

confidence: 99%

Short-term variability and mass loss in Be stars

Rivinius

Baade

Carciofi

2016

A&A

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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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“…Alternatively, according to seismic modelling performed by Saio and collaborators (e.g. Cameron et al 2008), one could consider f = 0.00848 c d −1 to be a pulsation mode with m = 0. Hence, f 5 and f 9 would then be the combination frequencies of this zonal mode and f 2.…”

Section: Beating Effectsmentioning

confidence: 99%

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

Neiner¹,

Gutiérrez‐Soto²,

Baudin

et al. 2009

A&A

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Context. HD 181231 is a B5IVe star, which has been observed with the CoRoT satellite during ∼5 consecutive months and simultaneously from the ground in spectroscopy and spectropolarimetry. Aims. By analysing these data, we aim to detect and characterize as many pulsation frequencies as possible, to search for the presence of beating effects possibly at the origin of the Be phenomenon. Our results will also provide a basis for seismic modelling. Methods. The fundamental parameters of the star are determined from spectral fitting and from the study of the circumstellar emission. The CoRoT photometric data and ground-based spectroscopy are analysed using several Fourier techniques: Clean-ng, Pasper, and Tisaft, as well as a time-frequency technique. A search for a magnetic field is performed by applying the LSD technique to the spectropolarimetric data. Results. We find that HD 181231 is a B5IVe star seen with an inclination of ∼45 degrees. No magnetic field is detected in its photosphere. We detect at least 10 independent significant frequencies of variations among the 54 detected frequencies, interpreted in terms of non-radial pulsation modes and rotation. Two longer-term variations are also detected: one at ∼14 days resulting from a beating effect between the two main frequencies of short-term variations, the other at ∼116 days due either to a beating of frequencies or to a zonal pulsation mode. Conclusions. Our analysis of the CoRoT light curve and ground-based spectroscopic data of HD 181231 has led to the determination of the fundamental and pulsational parameters of the star, including beating effects. This will allow a precise seismic modelling of this star.

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MOSTDetects SPBe Pulsations in HD 127756 and HD 217543: Asteroseismic Rotation Rates Independent ofv sin i

Cited by 46 publications

References 38 publications

Seismic modelling of OB stars

Seismic modelling of OB stars

Short-term variability and mass loss in Be stars

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

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