Gamma Draconis: Transition Region and Coronal Activity Beyond ''the Coronal Dividing Line''

Details Gamma Draconis: Transition Region and Coronal Activity Beyond ''the Coronal Dividing Line'' Gamma Draconis: Transition Region and Coronal Activity Beyond ''the Coronal Dividing Line''

Jul 1995

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995hst..prop.6068b&link_type=abstract

HST Proposal ID #6068

Physics

Hst Proposal Id #6068 Cool Stars

Scientific paper

Gamma Draconis is the first, normal, single late K giant (K5 III) located on the red side of the coronal ``dividing line'' that shows conclusive evidence for hot (~ 10^5 K) transition region (TR) and coronal plasma. Gamma Dra also has a cool stellar wind with a peak outflow velocity of 70 kms. This star is the first convincing example of a luminosity class III hybrid-chromosphere star that is not part of a binary system. We propose to measure the physical properties of the TR and wind of Gamma Dra by observing emission lines reflecting the electron density and atmospheric dynamics using the GHRS. Gamma Dra allows us to study stellar atmospheric properties at the lowest levels of magnetic activity observable. Density-sensitive lines of O IV, OV, Si III, and C III will be used to estimate the TR electron density, while the C II intersystem multiplet will give chromospheric densities. These optically-thin emission lines are also accurate tracers of turbulent and flow velocities. Characteristics of the wind flow will be measured using the absorption features seen in Fe II emission lines with a variety of optical depths. These results will be compared with our earlier observations of coronal and non-coronal cool stars.

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