2M1938+4603: A rich, multimode pulsating sdB star with an eclipsing dM companion observed with Kepler

R. H. Østensen, E. M. Green, S. Bloemen, T. R. Marsh, J. B. Laird, M. Morris, E. Moriyama, R. Oreiro, M. D. Reed, S. D. Kawaler, C. Aerts, M. Vučković, P. Degroote, J. H. Telting, H. Kjeldsen, R. L. Gilliland, J. Christensen-Dalsgaard, W. J. Borucki, D. Koch

Research output: Contribution to journalLetterpeer-review

75 Scopus citations


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 i = 69°45 ± 0°20, and find that the masses of the components are M1 = 0.48 ± 0.03 M and M2 = 0.12 ± 0.01 M.

Original languageEnglish (US)
Pages (from-to)L51-L55
JournalMonthly Notices of the Royal Astronomical Society: Letters
Issue number1
StatePublished - Oct 2010


  • Binaries: close
  • Binaries: eclipsing
  • Stars: individual: 2M1938+4603
  • Stars: variables: general
  • Subd-warfs

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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