AAS 197, January 2001
Session 8. Circumstellar Matter and Winds
Display, Monday, January 8, 2001, 9:30am-7:00pm, Exhibit Hall

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[8.03] On the Temperature Structure of \alpha~TrA's Wind

G. M. Harper, A. Brown, T. R. Ayres, R. A.. Osten, P. D. Bennett, J. L. Linsky, S. L. Skinner (CASA, U. of Colorado), S. Redfield, R. Baade (JILA, U. of Colorado & NIST), D. Reimers (Hamburger Sternwarte), B-G Andersson (Johns Hopkins University)

We present new constraints on the wind temperature structure of the hybrid bright-giant \alpha~TrA (K2 II) based on multi-wavelength datasets (ATCA, HST/GHRS & STIS, FUSE, ASCA). A previous study by Dupree & Brickhouse (1998), based on an ORFEUS-SPAS II spectrum, suggested that \alpha~TrA's wind temperature was 3 \times 105~K but this appears inconsistent with the line profile shapes of lower excitation species observed in GHRS spectra. The GHRS profiles indicate an ionization temperature at the base of the wind of Tion \le 20,000~K (Harper 2001).

We present new high sensitivity and R~20,000 spectral resolution FUSE spectra which allow us to examine the C~III 977Å\ and O VI line profiles in detail. Contrary to the ORFEUS-SPAS II spectra, the O~VI lines show no evidence that they are physically associated with the stellar wind. To within the inherent uncertainties in the FUSE wavelength scale, the O~VI 1031.9Å\ line is symmetric when centered on the photospheric rest frame. This indicates that (i) O~VI photons are not created within a 3 \times 105~K outflow, and (ii) there is no significant material at this temperature to scatter photons within the wind.

We also investigate the suggestion by Ayres & Kashyap (1994) that the large asymmetry observed in the H~Ly\alpha line, which is also observed in the FUSE Ly\beta profile, is a result of trace neutral hydrogen in a high velocity (400\>{\rm km\>s}-1) coronal wind.

This research is funded by NASA grants NAG5-9010 & NAG5-3226.

The author(s) of this abstract have provided an email address for comments about the abstract: gmh@casa.colorado.edu

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