Abstract

2M1938+4603 (KIC 9472174) displays a spectacular light curve dominated by a strong reflection effect and rather shallow, grazing eclipses. The orbital period is 0.126 d, the second longest period yet found for an eclipsing sdB+dM, but still close to the minimum 0.1-d period among such systems. The phase-folded Kepler light curve was used to detrend the orbital effects from the data set. The amplitude spectrum of the residual light curve reveals a rich collection of pulsation peaks spanning frequencies from ∼50 to 4500 μHz. The presence of a complex pulsation spectrum in both the p- and g-mode regions has never before been reported in a compact pulsator. Eclipsing sdB+dM stars are very rare, with only seven systems known and only one with a pulsating primary. Pulsating stars in eclipsing binaries are especially important since they permit masses derived from seismological model fits to be cross-checked with orbital mass constraints. We present a first analysis of this star based on the Kepler 9.7-d commissioning light curve and extensive ground-based photometry and spectroscopy that allow us to set useful bounds on the system parameters. We derive a radial-velocity amplitude K1 = 65.7 ± 0.6 km s −1, inclination angle graphic, and find that the masses of the components are M1 = 0.48 ± 0.03 M⊙ and M2 = 0.12 ± 0.01 M⊙.

Department(s)

Physics, Astronomy, and Materials Science

Document Type

Article

DOI

https://doi.org/10.1111/j.1745-3933.2010.00926.x

Rights Information

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2010 The authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

Keywords

binaries close, binaries eclipsing, stars individual, 2M1938+4603, subdwarfs, stars variables, stars general

Publication Date

2010

Journal Title

Monthly Notices of the Royal Astronomical Society

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