A Synthetic Spectrum and Light-Curve Analysis of the Cataclysmic Variable IX Velorum

Abstract

Spectrum synthesis analysis of FUSE and STIS spectra for the cataclysmic variable IX Vel shows that it is possible to achieve a close synthetic spectrum fit with a mass transfer rate of M˙=5×10^-9 M_solar yr^-1 and a modified standard model temperature profile. The innermost four annuli of the accretion disk model, extending to r/r_WD~4, are isothermal; beyond that limit the temperatures follow the standard model. A light synthesis fit to K-band photometry requires shallow eclipses of the accretion disk rim and secondary star limb. The geometry constrains the orbital inclination to i=57^deg+/-2^deg. The synthetic light curve requires a vertically extended accretion disk rim, beyond that predicted by gravitational equilibrium, to shadow the secondary star. The enhanced vertical extension is consistent with recent MHD predictions for CV accretion disks. Matching differing observed heights of alternate K-band light-curve maxima requires a warm rim region downstream of the intersection point of the mass transfer stream with the accretion disk rim. The temperature of the warm region is inconsistent with expectation for a bright spot associated with a rim shock.

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 Spectroscopic Explorer, which is operated for NASA by Johns Hopkins University under NASA contract NAS5-32985.