The nature of the companion to omicron Ceti
Abstract
The star o Ceti is a visual binary system composed of a red giant (Mira A) and a small blue companion. The companion (Mira B) is a white dwarf which intereacts with the stellar wind from Mira A. Mira B captures a portion of the stellar wind which forms an accretion disk surrounding the white dwarf. It is the light from the accretion disk which produces the visible companion. This work reports on photometry obtained in 1975 which exhibits two outbursts substantially larger than the normal background fluctuations in accretion disks. The possibility that Mira B might actually be a cataclysmic binary (CB) was investigated and radial velocity data was obtained in a search for periodic variations on the time scale of CB orbital periods. The white dwarf + accretion disk model and the CB model of Mira B are compared. The CB model of Mira B is rejected due to (1) insufficient mass in the system, (2) the size of the outbursts are too small even after removing the background contribution from Mira A, (3) there is no evidence of short-term periodicity in the radial velocities. The mass of Mira as determined from the orbit is strongly dependent on the adopted distance. A larger distance can remove the first objection to the CB model. The accretion disk model is consistent in a general way with the observations but details are sometimes inconsistent with the system parameters adopted in other works. Stellar wind accretion in detached systems provide important information on the outburst mechanism in cataclysmic variables. The occurrence of outbursts in Mira's accretion disk supports this as the site for the mechanism responsible for CV outbursts.
Degree
Ph.D.
Advisors
Moffett, Purdue University.
Subject Area
Astronomy|Astrophysics
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