Spitzer Space Telescope - General Observer Proposal #60107


Investigating the Nature of Dust Disks in Weakly-Magnetic Cataclysmic Variables

Principal Investigator: Kunegunda Belle
           Institution: Los Alamos National Laboratory

     Technical Contact: Donald Hoard, IPAC, California Institute of Technology

Co-Investigators: 
D. W. Hoard, Spitzer Science Center                                   
Steve B. Howell, NOAO                                                 

Science Category: compact objects 
 Observing Modes: IRAC Post-Cryo Mapping
  Hours Approved: 20.4 

Abstract:
We propose to obtain 4.5 micron light curves and a single 3.6 micron measurement
of four intermediate polars, a class of weakly-magnetic cataclysmic variables
(CVs), in order to investigate the nature of dust in CVs. This proposal is
motivated by results from our Cycle 2 observations, in which we discovered the
presence of circumbinary dust disks in highly-magnetic CVs, and our Cycle 4
observations, in which 4.5 and 8 micron light curves of the non-magnetic CV, WZ
Sge, revealed the presence of previously undetected dust associated with the
accretion disk within the binary. This dichotomy in dust properties may be the
result of evolutionary differences between highly-magnetic and non-magnetic CVs,
or the different accretion processes occurring within the systems. Intermediate
polars present a blend of non-magnetic and highly-magnetic CV properties, and
therefore, Spitzer time-series observations of these systems will help to answer
many of the questions that arose after our Cycle 2 and Cycle 4 observations, and
will also answer outstanding questions about intermediate polars, such as if
they are evolutionarily linked to highly-magnetic systems and how the cool
component of the accretion disk is affected by the truncation of the hot inner
component of the disk. The proposed observations will also have great relevance
for our understanding of the physics and structure of accretion disks in
general, those in binary systems as well as in active galaxies.