Observations of Symbiotic Stars with the Astro-2 Mission

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Session 30 -- First Results from Astro 2
Oral presentation, Tuesday, June 13, 1995, 2:00pm - 5:30pm

[30.07] Observations of Symbiotic Stars with the Astro-2 Mission

B.R. Espey (JHU/U. Pitt.), R.E. Schulte-Ladbeck (U. Pitt.), G.A. Kriss (JHU), F.W. Hamann III (CASS, UCSD), J.J. Johnson (U. Wisconsin, Madison), H.M. Schmidt (MSSO)

We present an overview of the data obtained on symbiotic stars during the successful Astro-2 mission, choosing as examples the spectra of two objects \--- RR Tel and EG And \--- which show different aspects of the symbiotic phenomenon.

Excellent spectra were obtained for RR Tel which show the presence of excited species in the FUV data including the highest excitation species \--- Ne$^{5+}$ \--- seen to date in a symbiotic star spectrum. The $\sim18$\ spectral features in the HUT data between $912 - 1200$\AA\ and simultaneous coverage to $\sim 1820$\AA\ permit a re-examination of physical conditions in the nebular material and determination of the relative importance of collisional, as opposed to radiative, excitation.

In addition, we will report on the first moderate resolution FUV spectrum of EG And. As the hot star was coming out of eclipse at the time of observation, HUT data reveal the presence of FUV absorption of the hot continuum. The presence of HI and H$_2$\ absorption features together with absorption from low ionization species provides the first detailed view of a red giant atmosphere in this spectral region. The importance of these measurements for models of red giant mass loss will be reviewed.

We will concentrate on the FUV portion of the spectra which is not observable with IUE. However, for RR Tel, we shall also discuss the results of simultaneous ground-based observations of lines which are attributed to Raman-scattering of the OVI 1032, 1038\AA\ doublet (see, e.g. , Schmid \& Schild 1994 A\&A 281 , 145 and references therein). The scattering process is postulated to take place in the wind of the giant component of the symbiotic system, but this is the first occasion we know of in which simultaneous data is available with which to test this hypothesis.

This work was funded by NASA grant NAS 5-27000 to the Johns Hopkins University and by NAG 8-1049 to the University of Pittsburgh.

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