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Session 6 - Novae and Supernovae.
Display session, Monday, June 08
Atlas Ballroom,

[6.05] Spectrum Synthesis of Accretion Disks in Partial Eclipse

R. A. Wade, J. Orosz (Penn State University)

We have modified our synthetic spectrum code for accretion disks in binary star systems, to deal with the case of a disk that is partially eclipsed by the mass-losing star. As in all eclipse mapping procedures used to study disks in binaries, the known Roche geometry of the binary system permits the correspondence to be made between the spectrum observed over some phase interval and the region of the disk that contributes to the spectrum. Our code can generate simulated observations corresponding to arbitrary phase intervals, with arbitrary spectral sampling and resolution. This capability clearly includes generating broad-band light curves as a limiting case. At present, our input (local, restframe) spectra are from non-irradiated LTE models self-consistently computed using I.\ Hubeny's TLUSDISK and SYNSPEC codes, and contain all relevant lines (typically thousands) from the Kurucz CD-ROM distribution. We use angle-dependent specific intensities, so limb darkening effects are automatically taken into account.

We present trailed-spectrogram and other representations of the partially-eclipsed disk spectrum as a function of orbital phase, for portions of the mid- and far-ultraviolet spectral regions accessible to HST and FUSE. We illustrate the behavior of blended features through eclipse and comment on the sensitivity of the synthesized spectra to the parameters of the input model, such as the stellar masses, mass transfer rate, and orbital inclination. Compared with out-of-eclipse spectra of the entire disk, observations during eclipse have the advantage for diagnostic purposes of showing deeper individual lines, (2) less blending of lines, and (3) an effectively smaller range of effective temperatures contributing to the observed spectrum. These advantages are especially important in analysis of the ultraviolet spectra of disks.

Supported by NASA grant NAG 5-3459 and STScI grants GO-3683.03 and GO-06661.01.

Program listing for Monday