A $\widetilde{\chi}^2$ analysis of standard model accretion disk syntheticspectrum fits to combined $FUSE$ and STIS spectra of V3885 Sagittarius, on anabsolute flux basis, selects a model that accurately represents the observedSED. Calculation of the synthetic spectrum requires the following systemparameters. The cataclysmic variable secondary star period-mass relationcalibrated by Knigge in 2007 sets the secondary component mass. A mean whitedwarf (WD) mass from the same study, that is consistent with anobservationally-determined mass ratio, sets the adopted WD mass of$0.7M_{\odot}$, and the WD radius follows from standard theoretical models. Theadopted inclination, $i=65{\arcdeg}$, is a literature consensus, and issubsequently supported by $\widetilde{\chi}^2$ analysis. The mass transfer rateis the remaining parameter to set the accretion disk $T_{\rm eff}$ profile, andthe $Hipparcos$ parallax constrains that parameter to$\dot{M}=5.0{\pm}2.0{\times}10^{-9} M_{\odot} {\rm yr}^{-1}$ by a comparisonwith observed spectra. The fit to the observed spectra adopts the contributionof 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.
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