Krzysztof Z. Kamiński et al. 2007 The Astronomical Journal 134 1206 doi:10.1086/520923
Krzysztof Z. Kamiński1, Slavek M. Ruciński2, Jaymie M. Matthews3, Rainer Kuschnig3, Jason F. Rowe3, David B. Guenther4, Anthony F. J. Moffat5, Dimitar Sasselov6, Gordon A. H. Walker7 and Werner W. Weiss8
Show affiliationsThe Hyades K2 V + WD system 471 Tau is a prototype post-common envelope system and a likely cataclysmic binary progenitor. We present 10 days of nearly continuous optical photometry by the MOST (Microvariability and Oscillations of Stars) satellite and partly simultaneous optical spectroscopy from DDO (David Dunlap Observatory) of the binary. The photometric data indicate that the spot coverage of the K dwarf component was less than observed in the past, suggesting that we monitored the star close to a minimum in its activity cycle. Despite the low spot activity, we still detected seven flarelike events whose estimated energies are among the highest ever observed in V471 Tau and whose times of occurrence do not correlate with the binary orbital phase. A detailed O - C analysis of the times of eclipse over the last ~35 years reveals timing variations which could be explained in several ways, including perturbations by an as-yet-undetected third body in the system or by a small orbital eccentricity inducing slow apsidal motion. The DDO spectra result in improved determinations of the K dwarf projected rotation velocity, VK sin i = 92 km s-1, and the orbital amplitude, KK = 150.5 km s-1. The spectra also allow us to measure changes in Hα emission strength and radial velocity variations. We measure a larger Hα velocity amplitude than found previously, suggesting that the source of the emission in V471 Tau was less concentrated around the sub-white dwarf point on the K star than had been observed in previous studies.
binaries: close; binaries: eclipsing; stars: variables: other; techniques: photometric
Issue 3 (2007 September)
Received 2007 April 10, accepted for publication 2007 June 14
Published 2007 July 26
Krzysztof Z. Kamiński et al. 2007 The Astronomical Journal 134 1206
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