IUE Observations of the Interacting S-Star Binary HR 1105
Session 46 -- Late Type Stars
Display presentation, Wednesday, 9:20-6:30, Heller Lounge Room

## [46.16] IUE Observations of the Interacting S-Star Binary HR 1105

T.B. Ake (CSC/GHRS), H.R. Johnson (Indiana U.), B.W. Bopp (U. Toledo)

We report on IUE observations of HR 1105, a symbiotic-like, interacting system comprised of an S3.5/2 red giant primary and hot companion. The UV flux is highly phase dependent for this 596-day period binary. At inferior conjunction of the hot object, continuum emission, high ionization permitted lines (C~IV, Si~IV, and N~V), and nebular lines (C~III], Si~III], and O~III]) are all intense. At other phases, these features weaken and can nearly disappear. High dispersion observations of Mg~II h and k have been obtained and profile shifts indicate these lines follow the red giant star. O~I $\lambda1300$ is also present, and although variable, is not orbitally modulated like the other UV features. Thus the Mg~II and O~I lines likely arise from the chromosphere of the S star, while the rest of the UV flux is the result of a stream or accretion disk around the secondary star. The absence of Tc in the photospheric spectrum of the red giant (Vanture et al, ApJ, 381, 278, 1991), evidence of gas streaming in He~I $\lambda 10830$ (Shcherbakov and Tuominen, A\&A, 255, 215, 1992), and the IUE data are consistent with the S star not being a thermally-pulsing asymptotic giant branch (AGB) star, but rather has been polluted by s-process material when the current secondary was a peculiar red giant.