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C. Froning, E. L. Robinson, W. F. Welsh (U. Texas at Austin), J. Wood (Keele University)
We present near-infrared, H- and K-band observations of the eclipsing, quiescent dwarf nova, IP Peg, and the eclipsing, novalike cataclysmic variable, RW Tri. The light curves are composed of ellipsoidal variations from the late-type secondary star and emission from the accretion disk and the bright spot. The light curves have two eclipses: a primary eclipse of the accretion disk and the bright spot by the companion star, and a secondary eclipse of the companion star by the disk. The ellipsoidal variations of the secondary star in each system were modeled and subtracted from the data.
The resulting H-band light curve in IP Peg shows a pronounced double-hump variation which resembles the double-hump profiles seen in the light curves of the dwarf novae WZ Sge and AL Com and likely originates in the accretion disk. The primary eclipse was modeled using maximum entropy disk mapping techniques. The results show that the near-infrared accretion disk has a flat intensity distribution and a cool brightness temperature (Tbr ~q 3000 K). Superimposed on the face of the disk is the bright spot (Tbr ~q 10,000 K); the position of the bright spot does not correspond to the theoretical mass stream trajectory nor to the observed positions of the bright spot at visual wavelengths. The flat radial brightness temperature profile resembles those of other quiescent, eclipsing dwarf novae. The presence of the secondary eclipse indicates that the disk is not optically thin, but the secondary eclipse is too shallow to be caused by a completely opaque disk, either. The near-infrared disk flux in IP Peg is a mixture of optically thick and optically thin emission, although the optically thin component appears to dominate.
A comparison of the near-infrared light curves and the properties of the accretion disks in IP Peg and RW Tri will be discussed.
The author(s) of this abstract have provided an email address for comments about the abstract: cyndi@astro.as.utexas.edu