Planck-cmb-allsky

Visual and Infrared Photometry of the Ultrashort Period Dwarf Nova HT Cassiopeiae

November 1987 • 1987AJ.....94.1291B

Authors • Berriman, Graham • Kenyon, Scott • Boyle, Charles

Abstract • This paper presents simultaneous visual (V) and infrared (H) photometry of the eclipsing dwarf nova binary HT Cas during two eclipses in October 1985, and infrared (JHK) photometry out of eclipse in January 1986. These are the first infrared observations of this object. They require that the red dwarf is fainter than Fν = 0.5 mJy at H(H = 15.7), and that the system is at least 215 pc away, for a red dwarf radius of RR = 0.15 R_sun;. At this distance, the white dwarf has a brightness temperature at V of Tb = 26000K. The accretion disk around the white dwarf is highly variable from epoch to epoch: it was 70% brighter at H in January 1986 than in October 1985. Such variability in a quiescent system is unprecedented. The disk consisted of optically thin material in January, when it had a kinetic temperature of Tkin = 10000 - 20000K, and was most likely optically thin in October too.

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Bruce Berriman

Senior Scientist