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 absorption at other phases, and strong blueshifted and redshifted emission outside primary eclipse. The absorption seen during primary eclipse is produced by circumstellar gas extending above and below the orbital plane and between us and the partially eclipsed primary star. The circumstellar material is in the form of a rotating disk because double-peaked emission features are visible at most phases outside primary eclipse, 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 addition, this rotating disk is asymmetric since the difference profiles seen 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 evidence that the circumstellar gas varied between 1991 and 1992, but the profiles were relatively unchanged during intervals less than four orbital cycles. Our results also support previous reports that the primary star rotates up to four times the synchronous rate. This high rotational 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 observed between phases 0.65 and 0.11 and is found primarily in the region 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, after beta Per, in which there is convincing evidence of a transient accretion disk.