EPIC 228782059: Asteroseismology of what could be the coolest pulsating helium-atmosphere white dwarf (DBV) known?

Abstract

We present analysis of a new pulsating helium-atmosphere (DB) white dwarf, EPIC~228782059, discovered from 55.1~days of {\em K2} photometry. The long duration, high quality light curves reveal 11 independent dipole and quadruple modes, from which we derive a rotational period of $34.1\pm 0.4$~hr for the star. An optimal model is obtained from a series of grids constructed using the White Dwarf Evolution Code, which returns $M_{\ast }=0.685\pm 0.003M_{\odot }$, $T_{\mathrm{eff}}=21,910\pm 23$\,K and $\log g=8.14\pm 0.01$\,dex. These values are comparable to those derived from spectroscopy by Koester \& Kepler ($20,860\pm 160$\,K and $7.94\pm 0.03$\,dex). If these values are confirmed or better constrained by other independent works, it would make EPIC~228782059 one of the coolest pulsating DB white dwarf star known, and would be helpful to test different physical treatments of convection, and to further investigate the theoretical instability strip of DB white dwarf stars.

9 pages, 5 figures, 2 tables, accepted by ApJ

References in corpus (9)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• The K2 Mission: Characterization and Early results
• A Technique for Extracting Highly Precise Photometry for the Two-Wheeled Kepler Mission
• Pulsating White Dwarf Stars and Precision Asteroseismology
• White Dwarf Rotation as a Function of Mass and a Dichotomy of Mode Linewidths: Kepler Observations of 27 Pulsating DA White Dwarfs Through K2 Campaign 8
• A deep test of radial differential rotation in a helium-atmosphere white dwarf: I. Discovery of pulsations in PG 0112+104
• TESS first look at evolved compact pulsators : Discovery and asteroseismic probing of the g-mode hot B subdwarf pulsator EC 21494-7018
• On The Impact Of 22Ne On The Pulsation Periods Of Carbon-Oxygen White Dwarfs With Helium Dominated Atmospheres

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