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Session 25 - Stars in the Ultraviolet.
Display session, Tuesday, June 10
South Main Hall,

[25.03] High-Dispersion UV Spectroscopy of Mira Variables with HST/GHRS

D. G. Luttermoser, S. Mahar (East Tenn. St. U.)

We report on the first set of UV spectra taken of Mira stars under high dispersion with the Goddard High Resolution Spectrograph (GHRS) onboard the Hubble Space Telescope (HST). Two spectral regions were observed, 2320 Å\ -- 2368 Å\ to record the C II] (UV0.01) multiplet and 2785 Å\ -- 2835 Å\ to obtain the Mg II h amp; k lines, for two Mira variables stars: R Hya, taken on 9 July 1996 (phase 0.26), and R Leo, taken on 14 January 1997 (phase 0.12). The R Hya Mg II spectrum is very clean and shows overlying absorption from Fe I (UV3) and Mn I (UV1) over the k line. The fluoresced Fe I (UV44) feature at 2824 Å\ is plainly visible in this spectrum, whereas past IUE observations at high dispersion were unable to record this feature. Remarkably, the newly identified fluoresced Fe I (UV45) feature near 2807 Å\ feature is seen in this spectrum. Until now, this line has only been seen in cool carbon stars with HST/GHRS. It is remarkable in that it is pumped by the thin C II] (UV0.01) emission line at 2325.5 Å\ in the carbon stars. This line is the likely pump in the oxygen-rich Miras in our sample as well. Two of the strongest C II] (UV0.01) near 2325 Å\ are barely detectable in our spectrum. This region of the spectrum is dominated by weak Si II] (UV0.01) near 2335 Åopposite to what is observed in the carbon stars. Very weak Mg II lines are seen in the R Leo spectrum at phase 0.12. At this phase, these lines are typically absent in IUE spectra.

This work is supported by NASA/STSCI grant GO-06620.01-95A. Ms.\ Mahar is an undergraduate student at East Tennessee State University who is assisting in the data analysis.

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