Variability of newly identified B-type stars observed by Kepler

Abstract

Recent re-determination of stellar atmospheric parameters for a sample of stars observed during the Kepler mission allowed to enlarge the number of Kepler B-type stars. We present the detailed frequency analysis for all these objects. All stars exhibit pulsational variability with maximum amplitudes at frequencies corresponding to high-order g modes. Peaks that could be identified with low-order p/g modes are also extracted for a few stars. We identified some patters in the oscillation spectra that can be associated with the period spacings that can results from the asymptotic nature of the detected pulsational modes. We also tentatively confront the observed oscillation characteristics with predictions from linear nonadiabatic computations of stellar pulsations. For high-order g modes the traditional approximation was employed to include the effects of rotation on the frequency values and mode instability.

Towards a systematic treatment of observational uncertainties in forward asteroseismic modelling of gravity-mode pulsators

“…Such stars have typically been found to exhibit prograde (m = 1) or zonal (m = 0) dipole ( = 1) modes spanning from a few to tens of consecutive radial order modes. Although a non-negligible fraction of these stars have dipole retrograde (m = −1) patterns, or those formed of quadrupole ( = 2) modes (Degroote et al 2010;Pápics et al 2011Pápics et al , 2014Pápics et al , 2015Pápics et al , 2017Christophe et al 2018;Szewczuk et al 2021;Pedersen et al 2021). The choices of how to extract and identify the pulsation mode frequencies, however, can differ in the literature.…”

“…A veritable revolution in the amount and quality of time series data assembled by the CoRoT (Auvergne et al 2009), Kepler/K2 (Borucki et al 2010;Koch et al 2010;Howell et al 2014), BRITE (Weiss et al 2014(Weiss et al , 2021 and now TESS (Ricker et al 2015) space missions have provided the necessary continuous, high-precision and long-term data for detailed asteroseismic modelling studies (Aerts 2015;Bowman 2020). Light curves from space missions have driven increasingly more sophisticated g-mode modelling methods to be developed, which have tested the impact of rotation, interior mixing, convection and opacity tables on the resultant stellar pulsation frequencies (Moravveji et al 2015(Moravveji et al , 2016Buysschaert et al 2018;Szewczuk & Daszyńska-Daszkiewicz 2018;Wu & Li 2019;Mombarg et al 2019;Szewczuk et al 2021;Pedersen et al 2021;Michielsen et al 2021). Recently, Aerts et al (2018) introduced the Mahalanobis distance (MD) within a g-mode forward asteroseismic modelling framework to appropriately deal with the strong correlations and degeneracies among model parameters, because it takes theoretical uncertainties into account.…”

“…In some cases multiple g-mode period spacing patterns for a star are plausible and it is not clear which of them are optimal for modelling (see e.g. Szewczuk & Daszyńska-Daszkiewicz 2018;Szewczuk et al 2021;Pedersen et al 2021).…”

The traditional approximation of rotation for rapidly rotating stars and planets

“…This was first obtained thanks to mixed pulsation modes splitted by rotation propagating in evolved low-and intermediate-mass stars (Beck et al 2012(Beck et al , 2014(Beck et al , 2018Mosser et al 2012;Deheuvels et al 2012Deheuvels et al , 2014Deheuvels et al , 2015Deheuvels et al , 2020Di Mauro et al 2016;Triana et al 2017;Gehan et al 2018;Tayar et al 2019). Then, observations of oscillation modes in F-and A-type stars (Kurtz et al 2014;Saio et al 2015;Bedding et al 2015;Keen et al 2015;Van Reeth et al 2015Schmid & Aerts 2016;Murphy et al 2016;Sowicka et al 2017;Guo et al 2017;Saio et al 2018Saio et al , 2021Mombarg et al 2019;Li et al 2019Li et al , 2020Ouazzani et al 2020) and in B-type stars (Pápics et al 2015(Pápics et al , 2017Triana et al 2015;Moravveji et al 2016;Kallinger et al 2017;Buysschaert et al 2018;Szewczuk & Daszyńska-Daszkiewicz 2018;Pedersen et al 2021;Szewczuk et al 2021) provided us new Rosetta stones to constrain the transport of angular momentum in the whole Hertzsprung-Russell diagram. More particularly, this pushes gravity-and gravitoinertial mode pulsators such as γ-Doradus and SPB stars at the forefront of this research.…”

An all-sky sample of intermediate- to high-mass OBA-type eclipsing binaries observed by TESS

“…The latter two Be stars were found to have gravito-inertial modes excited by the convective core (Neiner et al 2020), following the theory of gravito-inertial wave generation by Augustson et al (2020). Internal gravity waves excited by core convection have also been suggested as a physical explanation for the detected spectra of low-frequency stochastic variability found in large samples of intermediateand high-mass stars observed with CoRoT, Kepler, K2 (Kepler's second mission), and the NASA Transiting Exoplanet Survey Satellite (TESS) (Bowman et al 2019a(Bowman et al ,b, 2020Nazé et al 2021;Szewczuk et al 2021). While such a stochastically excited wave spectrum has not yet been used to probe internal physics, it is compatible with the predictions from large-scale multidimensional numerical simulations covering hundreds of convective turnover timescales (Edelmann et al 2019;Horst et al 2020;Ratnasingam et al 2020).…”