ERO Observation of Altair
Abstract
The A7 V star Altair (= HD 187642) occupies a unique position in the HR Diagram as the hottest star with late-type star characteristics. IUE, Einstein, and ROSAT observations show that Altair has ultraviolet emission lines and X-ray emission indicative of chromospheric and coronal plasma heated either by shock waves or magnetic reconnection events similar to the active late-type stars. Stars slightly hotter than Altair do not show these phenomena, apparently due to shallower convective zones. FUSE can obtain a rich FUV emission line spectrum that will likely contain C III, O VI, and the hydrogen Lyman emission lines. A FUSE spectrum of Altair will enable us to determine whether or not the relative heating rates for the 104, 105, and >106 K plasma follow the trends seen in the cooler stars, whether the heating is acoustic or magnetic in character, and whether the emission line shapes and Doppler shifts indicate a wind or interesting dynamics. A 5 ks exposure should obtain S/N in the range 16 to 33 per 0.032 A resolution element for the important emission lines.
- Publication:
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FUSE Proposal
- Pub Date:
- 1999
- Bibcode:
- 1999fuse.prop.X025L
- Keywords:
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- FUSE Proposal ID #X025