CIRCUMSTELLAR MATERIAL IN TX URSAE MAJORIS

The analysis of the Halpha difference profiles of TX UMa has revealed deep redshifted absorption during primary eclipse, weaker redshifted a bsorption at other phases, and strong blueshifted and redshifted emiss ion outside primary eclipse. The absorption seen during primary eclips e is produced by circumstellar gas extending above and below the orbit al plane and between us and the partially eclipsed primary star. The c ircumstellar material is in the form of a rotating disk because double -peaked emission features are visible at most phases outside primary e clipse, with the stronger component first redshifted near phase 0.16-0 .19 but blue-shifted half an orbit away near phase 0.65-0.66. In addit ion, this rotating disk is asymmetric since the difference profiles se en near phi = 0.25 are typically weaker, with strengths approximately 14% of the continuum flux, than those seen near the other quadrature, which have strengths as high as 18% of the continuum flux. There is ev idence that the circumstellar gas varied between 1991 and 1992, but th e profiles were relatively unchanged during intervals less than four o rbital cycles. Our results also support previous reports that the prim ary star rotates up to four times the synchronous rate. This high rota tional velocity is most likely due to the impact of the high-velocity gas stream on the star. In TX UMa, most of the circumstellar gas is ob served between phases 0.65 and 0.11 and is found primarily in the regi on between the two stars, symmetrically located at about the point of he impact between the gas stream and the primary. With these results, TX UMa is now only the second partially eclipsing Algol-type system, a fter beta Per, in which there is convincing evidence of a transient ac cretion disk.