New evidence of strong UV radiation in TT Ari.

Abstract

Three SWP spectra and one LWR spectrum of the cataclysmic variable TT Ari were obtained with the IUE satellite during three different brightness phases, including the brightness minimum of November 1980. The absolute continuum intensity distribution in the UV and optical regions is examined in relation to several steady-state optically thick accretion disk models. It is shown that the flux distribution cannot be represented by any of these models. The strong excess is in good agreement with an F_nu proportional to nu-squared power law, which is interpreted as the Rayleigh-Jeans tail of a soft X-ray thermal blackbody component with k(Tbb) 17 eV and maximum flux at 0.1-0.2 keV.