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| Paper: |
Searching for the Cause of Hybrid Star Activity |
| Volume: |
154, Cool Stars, Stellar Systems and the Sun: Tenth Cambridge Workshop |
| Page: |
1307 |
| Authors: |
Robinson, Richard D.; Carpenter, Kenneth G.; Brown, Alexander |
| Abstract: |
UV spectra for a wide range of chromospheric diagnostics have been obtained for the non-coronal giant alpha Tau and the `hybrid' star gamma Dra using the Goddard High Resolution Spectrograph. These stars have very similar spectral types and are very close to one another in mass, luminosity, size, effective temperature and gravity. A detailed comparison shows that the photosphere and chromosphere of the stars are very similar. The two stars show the same level of UV continuum emission and chromospheric turbulence and have Fe 2 emission profiles which are nearly identical. The amount of transition region plasma, as measured by the C 4 surface flux, is also nearly the same. The winds of these two stars, however, are significantly different. Preliminary models based on the O 1 (UV 2) and Mg 2 (UV 1) profiles show that the wind for alpha Tau has a terminal velocity of ~30 km s^{-1} and a much slower acceleration than the wind of gamma Dra, which has a terminal velocity of ~65 km s^{-1}. However, despite the different wind properties, the mass loss rate from these two stars is very similar. |
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