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Session 76 - Cataclysmic Variables and Accretion Disks.
Display session, Wednesday, January 15
We present a new eclipse mapping technique, which is able to map distributions in physical parameters of accretion disks in eclipsing cataclysmic variables.
The Physical Parameter Mapping Method is based on Horne's (1985, MNRAS, 213, 129) classical ``Eclipse Mapping Method'' (see also Baptista amp; Steiner, 1991, Aamp;A, 249, 284) which reconstructs intensity distributions of the accretion disk in eclipsing cataclysmic variables. Images are determined by the eclipse light curve and a maximum-entropy-method (MEM) (Skilling amp; Bryan 1984, MNRAS, 211, 111) leading to the smoothest image still compatible with the data. Instead of intensities we map physical parameter distributions within the accretion disk. In the simplest case, black body temperatures are determined by fitting several light curves simultaneously.
Multi-colour test eclipse light curves in UBVRJHK of an optically thick black body disc yield good fits. The general behaviour of the reconstructed temperature distribution resembles the original one very well, with only minor deviations at steep gradients. These deviations are due to the smearing character of the applied MEM algorithm.
The method allows furthermore to calculate both black body temperatures and deviations in form of intensity ratios in different passbands. This is especially interesting for outburst light curves, since they are believed to be caused by (close to) optically thick disks. Results for IP Peg during decline from outbursts will be presented.
Program listing for Wednesday