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Paper: The Quiescent Accretion Disk in IP Peg at Near-Infrared Wavelengths
Volume: 157, Annapolis Workshop on Magnetic Cataclysmic Variables
Page: 397
Authors: Froning, C. S.; Robinson, E. L.; Welsh, William F.; Wood, Janet H.
Abstract: We present near-infrared H-band (1.45-1.85 microns) observations of the eclipsing dwarf nova IP Peg in quiescence. The light curve is dominated by ellipsoidal variations from the late-type secondary star and emission from the accretion disk and the bright spot. The light curve shows a primary eclipse of the accretion disk and a secondary eclipse of the companion star by the disk. The contribution of the secondary star (i.e. the ellipsoidal variations) was modeled and subtracted from the data. The remaining light curve shows a pronounced double-hump variation. The variation resembles the double-hump profiles seen in the light curves of the dwarf novae WZ Sge and AL Com, which in these systems originates in the accretion disk. The primary eclipse was modeled using a maximum-entropy disk mapping technique. The results show that the near-infrared accretion disk has a flat intensity distribution and a low brightness temperature (Tbr = 3000 K). Superimposed on the face of the disk is the bright spot (Tbr = 10 000 K). The presence of the secondary eclipse in the light curve indicates that the disk is not transparent, but the eclipse is too shallow to be caused by a fully opaque disk. The near-infrared flux from the accretion disk in IP Peg is emitted from a combination of opaque and transparent material, with the optically thin component dominating the disk emission.
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