Rotation-Activity Relations for Cool Zero-Age Main Sequence (ZAMS) Stars.
Chromospheric and transition region (TR) rotation-activity relations are presented, based on HST/GHRS observations of a homogeneous group of 6 solar-neighborhood Pleiades Moving Group members. The 6 stars are all between spectral types K0 V and K2 V, i.e., they are just coming on to the Zero-Age-Main-Sequence (ZAMS). The GHRS fluxes generally agree well with fluxes measured by IUE, in particular, the GHRS data confirm the IUE result that the Mg 2 h+k fluxes are virtually saturated. However, for O 1 (lambda1304+lambda1306), which is also a chromospheric line, the flux level depends on rotation rate for periods longer than ~2-3 days. The slope of this relation is not as steep as that for the TR line, C 4 (lambda1548+lambda1551), as expected. We suggest that the different behaviors of Mg 2 and O 1 lies in their different excitation mechanisms.
|Main Author:||Ambruster, Carol W.|
|Other Authors:||Brown, Alexander., Fekel, Francis C., Harper, Graham M., Fabian, Dirk., Wood, Brian., Guinan, Edward F.|