Physics
Scientific paper
Aug 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000noao.prop..157f&link_type=abstract
NOAO Proposal ID #2000B-0157
Physics
Scientific paper
Cataclysmic variables (CVs) are outstanding test beds for studying the physics of accretion disks under a variety of conditions and stimuli. A number of fundamental questions concerning the structure of accretion disks in CVs remain unanswered, including the geometry and opacity of the continuum source and the emission line formation mechanism. Models in which the accretion disk is optically thin fail to reproduce the observed emission line strengths and predict variations in EW with binary inclination incompatible with observation. Vertically extended models in which the lines originate in a hot, transparent chromosphere overlying a cool, opaque disk are preferred, but recent near-infrared (NIR) observations of high-inclination CVs have shown that the cool bulk of the disk is primarily optically thin. These observations suggest an alternate picture of the accretion disk structure in which the disk is non-uniform and patchy, with localized regions of enhanced opacity. We propose to examine accretion disk structure by obtaining the first time-series NIR spectra of eclipsing CVs using OSIRIS on the CTIO 4-m telescope. The JHK colors will probe the optical depth of the disk continuum source, preferentially targeting the cool disk bulk rather than the hotter binary elements dominating the visible and UV wavelengths. We will use the secondary eclipse of the mass donor star--- seen only in the NIR---to determine the optical depth of the occulting accretion disk. We will use the primary eclipse and orbital phase- resolved spectra to map the accretion disk in both the lines and continuum, with which we will search for evidence of clumpy, non-uniform structure in the bulk of the disk and determine if disks are largely opaque with chromospheres or primarily transparent. Our results will impact general models of accretion disks both in CVs and in the more energetic disks of X-ray binaries and AGN.
Froning Cynthia S.
Long Knox S.
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