Physics – Plasma Physics
Scientific paper
Dec 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997hst..prop.7733a&link_type=abstract
HST Proposal ID #7733
Physics
Plasma Physics
Hst Proposal Id #7733 Cool Stars
Scientific paper
We will explore possible future fates of solar magnetic activity through high-S/N ultraviolet spectra of the ancient Sun analog, Arcturus {K2 III}. The fundamental mechanisms that drive the hot {T>10^6 K} coronae of cool stars remain elusive. Solving the mystery is a central theme of the ``solar-stellar connection;'' whose importance extends beyond astronomy to areas ranging from basic plasma physics to solar-terrestrial relations. A significant property of the activity is that it subsides with age: G dwarfs in young clusters are intense coronal sources, whereas old low mass K giants are so feable in soft X-rays that most are below current detection limits. For that reason, historical studies of activity have been biased towards the younger stars. Now HST/STIS easily can record faint coronal proxies {like Si IV and C IV} in nearby cool subgiants and giants, thereby mitigating the de facto age discrimination. In the solar neighborhood the brightest single star of advanced age {9-11 Gyr} is Alpha Bootis {K2 III}. Previous studies have placed the archetype red giant firmly in the ``coronal graveyard.'' Our project focuses on understanding the ``basal'' chromosphere; molecular cooling catastrophes and the structure of the passive ``COmosphere;'' the dynamics and energy balance of the residual subcoronal gas; and mass loss mechanisms. {This program is a carryover from a failed Cycle 5 GHRS observation.}
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