Other
Scientific paper
Jan 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993phdt........21w&link_type=abstract
PhD Dissertation, Indiana Univ. Bloomington, IN United States
Other
Cataclysmic Variables, Accretion Disks, Stellar Spectra, Stellar Spectrophotometry, White Dwarf Stars, Red Dwarf Stars, Magnetic Stars, Astronomical Photometry, Astronomical Spectroscopy, Classifications
Scientific paper
My research involves two members of the class of interacting binary star systems referred to as cataclysmic variables (CV's). The CV canonical model consists of a white dwarf and a red dwarf companion orbiting their common center of mass; material is siphoned from the red dwarf by the white dwarf, forming an accretion disk around the white dwarf. While classical novae are CV's, the two I have studied, CP Puppis (Nova Puppis 1942) and BT Monocerotis (Nova Monocerotis 1939), exhibit characteristics that appear to challenge this model. Using time-resolved spectrophotometric data on CP Pup and BT Mon, I performed photometric and spectroscopic analyses, as well as Doppler tomographic studies of these two CV's. CP Pup's Doppler tomograms show that the system harbors an accretion disk, but they also indicate unusual regions of enhanced emission on the backside of the disk. Further, my analyses demonstrate the existence of a photometric period 11% longer than the system's spectroscopic period. Such characteristics suggest that CP Pup may be a DQ Herculis system, characterized by a magnetic white dwarf that partially disrupts the accretion disk, an SU Ursae Majoris system, characterized by a processing accretion disk, or possibly a hybrid system that lies between these two established subclasses. In Doppler tomograms of BT Mon, however, there is no evidence of an accretion disk. In addition, high-velocity (approximately greater than 1000 km s-1) gas motions visible only during eclipse of the white dwarf and unique among CV's, suggest material from the red dwarf falls radially onto the white dwarf. I consider four models to explain the BT Mon observations, the most intriguing being that BT Mon is a long-period, column-accreting AM Herculis system, but find ultimately and unfortunately that a firm conclusion cannot be reached at this time. Although it is impossible to determine the exact natures of CP Pup and BT Mon without polarimetric observations and additional spectrophotometric observations, it is obvious that these two old novae are not accurately described by the canonical model; indeed, my research and that of others implies that unusual behavior in CV's is the norm rather than the exception.
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