Transition Layers of Hyades F Stars
Abstract
We would like to observe most Hyades F main sequence stars in order to determine the dependence of transition layer emission on temperature, rotation, binarity and Li abundances. In order to study the dependence on any one parameter one has to keep all other parameters constant. For the Hyades cluster age and metal abundance are constant. The Hyades cluster is the nearest one for which the F stars are bright enough to be observed with IUE in the SWP wavelength region. At the same time there are enough F stars to study the dependence on one parameter with all other parameters being nearly the same. In the F star region rotation decreases when going from early to late F stars. Simon and Drake suggest that the heating mechanism changes for B-V around 0.45. The chromospheric emission appears not to vary with time for stars earlier than F7 while it is variable for stars later than F8. Michaud suggests depletion of He for early F stars but not for late F stars. Boesgaard and Tripicco find a minimum in the Li abundances for stars with Teff around 6700 K. We want to study the changes (or not) in the transition layer emission related to all these events.
- Publication:
-
IUE Proposal
- Pub Date:
- 1992
- Bibcode:
- 1992iue..prop.4205B