Seismic modeling of a very young SPB star -- KIC8264293

Abstract

KIC8264293 is a fast rotating B-type pulsator observed by Kepler satellite. Its photometric variability is mainly due to pulsations in high-order g modes. Besides, we detected a weak H$\alpha$ emission. Thus, the second source of variability is the fluctuation in a disk around the star. The pulsational spectrum of KIC8264293 reveals a frequency grouping and period spacing pattern. Here, we present the thorough seismic analysis of the star based on these features. Taking into account the position of the star in the HR diagram and fitting the 14 frequencies that form the period spacing we constrain the internal structure of the star. We conclude that the star barely left the ZAMS and the best seismic model has $M=3.54{\mathrm{M}}_{\odot }$, $V_{\mathrm{rot}}=248{\mathrm{km}\mathrm{s}}^{-1}$ and $Z=0.0112$. We found the upper limit on the mixing at the edge of the convective core, with the overshooting parameter up to $f_{\mathrm{ov}}=0.03$. On the other hand, we were not able to constrain the envelope mixing for the star. To excite the modes in the observed frequency range, we had to modify the opacity data. Our best seismic model with an opacity increase by 100% at the "nickel" bump $\log T=5.46$ explains the whole instability. KIC8264293 is the unique, very young star pulsating in high-order g modes with the Be feature. However, it is not obvious whether the source of this circumstellar matter is the ejection of mass from the underlying star or whether the star has retained its protostellar disk.

Accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journal

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