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Published October 1, 2014 | Published + Accepted Version
Journal Article Open

HD 183648: a Kepler eclipsing binary with anomalous ellipsoidal variations and a pulsating component


KIC 8560861 (HD 183648) is a marginally eccentric (e = 0.05) eclipsing binary with an orbital period of P_(orb) = 31.973 d, exhibiting mmag amplitude pulsations on time-scales of a few days. We present the results of the complex analysis of high- and medium-resolution spectroscopic data and Kepler Q0 – Q16 long cadence photometry. The iterative combination of spectral disentangling, atmospheric analysis, radial velocity and eclipse timing variation studies, separation of pulsational features of the light curve, and binary light curve analysis led to the accurate determination of the fundamental stellar parameters. We found that the binary is composed of two main-sequence stars with an age of 0.9 ± 0.2 Gyr, having masses, radii and temperatures of M_1 = 1.93 ± 0.12 M_⊙, R_1 = 3.30 ± 0.07 R_⊙, T_(eff1) = 7650 ± 100 K for the primary, and M_2 = 1.06 ± 0.08 M_⊙, R_2 = 1.11 ± 0.03 R_⊙, T_(eff2) = 6450 ± 100 K for the secondary. After substracting the binary model, we found three independent frequencies, two of which are separated by twice the orbital frequency. We also found an enigmatic half orbital period sinusoidal variation that we attribute to an anomalous ellipsoidal effect. Both of these observations indicate that tidal effects are strongly influencing the luminosity variations of HD 183648. The analysis of the eclipse timing variations revealed both a parabolic trend, and apsidal motion with a period of P^(obs)_(apse) = 10400 ± 3000 y, which is ten times faster than what is theoretically expected. These findings might indicate the presence of a distant, unseen companion.

Additional Information

© 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2014 July 6. Received 2014 July 6; in original form 2014 May 29. This project has been supported by the Hungarian OTKA Grant K83790, ESA PECS Contract No. 4000110889/14/NL/NDe, the Lendület-2009 Young Researchers Programme of the Hungarian Academy of Sciences and the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 269194 (IRSES/ASK) and no. 312844 (SPACEINN). AD, RSz and GyMSz have been supported by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences. TB, BCs, JK and GyMSz would like to thank City of Szombathely for support under Agreement No. S-11-1027. This paper includes data collected by the Kepler mission. Funding for the Kepler mission is provided by the NASA Science Mission directorate. Based on observations obtained with the APO 3.5-m telescope, which is owned and operated by the Astrophysical Research Consortium. The authors wish to tank Dr. Gregory Feiden for calling their attention for a numerical error in an earlier version of the manuscript.

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Accepted Version - 1407.1788.pdf


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August 20, 2023
October 20, 2023