Temporal and Spectral Characteristics of X-Ray Bright Pleiads
Session 49 -- Associations and Clusters
Display presentation, Wednesday, 9:20-6:30, Pauley Room

## [49.09] Temporal and Spectral Characteristics of X-Ray Bright Pleiads

J.-P. Caillault, M. Gagn\'e, J. Yglesias (Univ. Georgia), L. Hartmann, C. Prosser, J. Stauffer (CfA)

ROSAT PSPC observations of the Pleiades have allowed us to analyze the spectral and temporal characteristics of the X-ray sources within the cluster. Of the $\sim$300 sources detected within the images, $\sim$20-30 of them seem to be variable at the 99\% confidence level ($\chi$$^2$-test). Numerous flares have also been found, the light curves of which we display. In addition, we have fit two-temperature Raymond-Smith thermal plasma models to the spectra of the $\sim$6 brightest sources and examined whether these sources behave in accordance with coronal loop models. We also demonstrate that the two-temperature fit changes during a flare. We have constructed composite spectra for both shallow and deep convective zone stars in order to see whether there is a systematic change of spectral characteristics from spectral type F to M. Finally, in an attempt to discern possible evolutionary effects, we compare our results with those from the older Hyades cluster (Stern et al. 1993).

This research was supported by NASA Grants NAG5-1608 to UGA and NAG5-1849 \& NAGW-2698 to the CfA.