The Quiescent Accretion disk in IP Peg at Near-Infrared Wavelengtths
C. S. Froning, E. L. Robinson, W. F. Welsh,
Department of Astronomy,
University of Texas at Austin, Austin, Texas, USA
and
J. H. Wood
Department of Physics,
Keele University, Keele, Staffordshire, England
We present near-infrared, H-band
(1.45 - 1.85 micrometer) observations
of the eclipsing dwarf nova, IP Peg, in quiescence.
The light curves are composed of ellipsoidal variations from
the late-type 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 were modeled
and subtracted from the data.
The resulting light curve shows a pronounced double-hump variation.
The double-hump profile resembles those seen in the light curves of WZ Sge
and AL Com and likely originates in the accretion disk.
The primary eclipse was modeled using maximum entropy disk
mapping techniques.
The accretion disk has a flat intensity distribution and a cool
brightness temperature (Tbr ~ 3000 K) in the
near-infrared.
Superimposed on the face of the disk is the bright
spot (Tbr ~ 10,000 K); the position
of the bright spot is different from the observed range of visible
bright spot positions.
The near-infrared accretion disk flux is dominated by optically thin emission.
The secondary eclipse indicates the presence of some
occulting medium in the disk, but the eclipse depth is too shallow
to be caused by a fully opaque accretion disk.