Session 103 - Cool Stars.
Display session, Thursday, January 18
North Banquet Hall, Convention Center

## [103.02] GHRS Observations of Solar Neighborhood ZAMS K Dwarfs

C. W. Ambruster (Villanova U.), A. Brown (CASA, U.CO), F. C. Fekel (COE, TN St.U.)

We are currently obtaining (Sep-Nov 1995) GHRS observations of a unique, homogeneous group of 6 solar neighborhood (8 \leq d \leq 40 pc) Pleiades Moving Group K0-K2 dwarfs (HD 197890, HD 1405, HD 82558, HD 220140, HD 82443, HD 17925). The only significant variable between these stars is rotation (8 hr \leq P_rot \leq 6.9 d), which is widely believed to be the single most important parameter behind non-radiative atmospheric activity at all levels of the atmosphere. In this poster, we will present the GHRS spectra, as well as a comparison of derived chromospheric and transition region (TR) properties as a function of rotation \rm. We will ultimately \rm\ use the GHRS spectra, combined with our EUVE, IUE, and ground-based observations of these stars to define the (currently unknown) upper atmospheric structure of a cool star at the point of hydrogen ignition, many years before transition region and coronal spectroscopy can be done on the nearest cluster ZAMS stars, the Pleiades early K dwarfs.