KQ Mon and the Nature of the UX Ursa Majoris Nova-Like Variables

Abstract

KQ Mon, a new UX UMa type nova-like variable discovered by H.E. Bond, exhibits optical spectra, UBV and high speed pnotometric characteristics strongly similar to other members of the UX Ursa Majoris subset. However its ultraviolet spectra when compared with other UX UMa stars shed considerable light on the nature of these objects. Its spectrum is dominated by strong broad highly ionized absorption lines including the NV, Si IV and CIV UV resonance doublets. No emission lines or P Cygni type features are evident and the velocity displacements are smaller suggesting the absence of a hot high velocity wind characterizing other UX UMa stars. A physical interpretation of the UV absorption spectra and optical spectra and their observed temporal variations is presented. Based upon (1) high mass accretion rates derived by fitting the observations with theoretical continuum fluxes from steady accretion disk models by R.E. Williams, (2) the presence of outflowing winds with the determination of corresponding mass loss rates and properties of the theoretical wind models by Cassinelli, Olson and Stalio, and (3) new time independent steady state disk structure computations, a model is suggested to explain the observed properties of the UX UMa stars and their lack of major outbursts.