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CCD Photometry and Preliminary Analysis of V865 Cygni
Ronald G. Samec, Scott A. Herr, James T. Zetzl and Tobias J. Kreidl
Publications of the Astronomical Society of the Pacific
Vol. 104, No. 671 (1992 January), pp. 29-37
Published by: Astronomical Society of the Pacific
Stable URL: http://www.jstor.org/stable/40679821
Page Count: 9
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CCD images of the thirteenth-magnitude variable V865 Cygni were taken on four consecutive nights in the summer of 1990. The 1.1-m Hall reflector telescope at Lowell Observatory was used in conjunction with an RCA CCD camera system. Four times of minimum light were determined and improved linear and quadratic ephemerides were calculated. A period study, spanning over a fortyyear interval, may indicate that the system is undergoing a continuous period increase of 5.4 × 10⁻ɸ day yr⁻ⁱ. In a conservative scenario, this would be an indication of a mass accretion by the primary, more massive, component. The V, R, and I light curves formed by the first precision photometry to be obtained on V865 Cygni show that it is an A-type W UMa system. However, the curves are somewhat incomplete since the maximum that follows the secondary eclipse was not covered. The first synthetic light-curve solution of V865 Cygni is also presented. This solution reveals that V865 Cygni is a contact binary consisting of two G spectral type components with a fillout of ~18% and a mass ratio of ~0.45. The component temperature difference is only ~110 K. A substantial hot spot region of ~34° diameter is proposed to model the asymmetry in the light curves following the observed maximum. We suggest that the origins of this region may be attributed to fluid dynamics rather than to the usual magnetic activity which is prevalent in late-type systems like V865 Cyg.
Publications of the Astronomical Society of the Pacific © 1992 The University of Chicago Press