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C. K. Henry, E. M. Sion (Villanova Un.)
VW Vulpecula and X Leo are two U Geminorum type dwarf novae, the latter with a newly found orbital period (0.16870±.00007 days). The inclination angle of VW Vul is known to be 44±2 deg, the mass of the white dwarf is 0.24±.06 Msun, a secondary mass of 0.14±.01 Msun and the system appears to have an outburst period of 14-24 days (Ritter & Kolb 2000). X Leo has nearly the same orbital period, outburst recurrence time and outburst amplitude but more uncertain orbital parameters. We have carried out an IUE archival comparative study of the two systems. We have applied the Massa-Fitzpatrick (2000) flux calibration correction to the archival IUE NEWSIPS SWP spectra of these two systems, obtained during dwarf nova quiescence. We have carried out high gravity model atmosphere using the codes TLUSTY195, SYNSPEC42, ROTIN and accretion disk synthetic spectra from the grid of Wade and Hubeny (1998). We have determined the physical properties of the white dwarf accreters, including temperature, gravity, chemical abundances estimates, and the accretion rate during quiescence. We discuss our results in the context of the overall picture of accretion physics in dwarf novae and the effects of accretion on the white dwarf.
This research was supported in part by NSF grant AST 99-01955, NASA ADP grant NAG5-8388 and by summer research funding from the NASA- Delaware Space Grant Colleges Consortium.