V3885 Sagittarius: A Comparison with a Range of Standard Model Accretion Disks

Abstract

A \widetilde{χ}^2 analysis of standard model accretion disk synthetic spectrum fits to combined Far Ultraviolet Spectroscopic Explorer and Space Telescope Imaging Spectrograph spectra of V3885 Sagittarius, on an absolute flux basis, selects a model that accurately represents the observed spectral energy distribution. Calculation of the synthetic spectrum requires the following system parameters. The cataclysmic variable secondary star period-mass relation calibrated by Knigge in 2006 and 2007 sets the secondary component mass. A mean white dwarf (WD) mass from the same study, which is consistent with an observationally determined mass ratio, sets the adopted WD mass of 0.7 M _sun, and the WD radius follows from standard theoretical models. The adopted inclination, i = 65°, is a literature consensus, and is subsequently supported by \widetilde{χ}^2 analysis. The mass transfer rate is the remaining parameter to set the accretion disk T _eff profile, and the Hipparcos parallax constrains that parameter to \dot{M}=(5.0± 2.0)× 10^{-9} M_{⊙} yr^{-1} by a comparison with observed spectra. The fit to the observed spectra adopts the contribution of a 57, 000 ± 5000 K WD. The model thus provides realistic constraints on \dot{M} and T _eff for a large \dot{M} system above the period gap.

Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS5-26555, and the NASA-CNES-CSA Far Ultraviolet Explorer, which is operated for NASA by the Johns Hopkins University under NASA contract NAS5-32985.