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

TL;DR

This study uses synthetic spectrum fitting to accurately model the accretion disk of V3885 Sagittarius, constraining key system parameters and validating the standard accretion disk model with observational data.

Contribution

It provides a detailed comparison of synthetic spectra with observations to determine system parameters, supporting the standard accretion disk model for V3885 Sagittarius.

Findings

Accurately constrained mass transfer rate of $5.0{ imes}10^{-9} M_{ m ext{sun}}/yr$

Validated the inclination angle of 65 degrees through spectral fitting

Determined the white dwarf temperature to be approximately 57,000 K

Abstract

A $\widetilde{\chi}^2$ analysis of standard model accretion disk synthetic spectrum fits to combined $FUSE$ and STIS spectra of V3885 Sagittarius, on an absolute flux basis, selects a model that accurately represents the observed SED. Calculation of the synthetic spectrum requires the following system parameters. The cataclysmic variable secondary star period-mass relation calibrated by Knigge in 2007 sets the secondary component mass. A mean white dwarf (WD) mass from the same study, that is consistent with an observationally-determined mass ratio, sets the adopted WD mass of $0.7M_{\odot}$, and the WD radius follows from standard theoretical models. The adopted inclination, $i=65{\arcdeg}$, is a literature consensus, and is subsequently supported by $\widetilde{\chi}^2$ analysis. The mass transfer rate is the remaining parameter to set the accretion disk $T_{\rm eff}$ profile, and the $Hipparcos$ parallax constrains that parameter to $\dot{M}=5.0{\pm}2.0{\times}10^{-9} M_{\odot} {\rm yr}^{-1}$ by a comparison with observed spectra. The fit to the observed spectra adopts the contribution of a $57,000{\pm}5000$K WD. The model thus provides realistic constraints on $\dot{M}$ and $T_{\rm eff}$ for a large $\dot{M}$ system above the period gap.