FUSE Survey of Cool Luminous Stars
Abstract
The FUSE telescope has been used to survey spectroscopically eight cool luminous stars (β Cet, α Ori,α Tau, α Car, β Gem, 31 Com, β Dra, α Aqr) in the spectral region λ λ 910--1180. Emission from O VI has been detected in all stars with the exception of α Ori, decreasing in surface flux across the giant branch. This demonstrates the pervasive extent of high temperature plasma ( ~ 3x 105K) to stars as late as K5 III (α Tau). Densities in the lower transition region ( ~ 70000K), as determined from C III line ratios, are on the order of 109 cm-3, with densities in the active stars 31 Com and β Cet perhaps as much as an order of magnitude higher. Emission from coronal plasma represented by Fe XVIII occurs in β Cet. Line profiles of individual species can be used to infer atmospheric heating and dynamics. Extended atmospheres are signaled by the presence of narrow Fe II emission that is fluoresced by H-Lyman α in the coolest stars including α Ori. These rich spectra document the energetics and dynamics of giant and supergiant atmospheres. Based on Guaranteed Team observations made with the NASA-CNES-CSA Far Ultraviolet Explorer which is operated for NASA by The Johns Hopkins University under NASA contract NAS5-32985.
- Publication:
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American Astronomical Society Meeting Abstracts
- Pub Date:
- December 2001
- Bibcode:
- 2001AAS...199.1310D