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Extreme Ultraviolet Explorer Right Angle Program observations of cool stars

The Extreme Ultraviolet Explorer (EUVE) Right Angle Program (RAP) obtains photometric data in four bands centered at 100 (Lexan/B), 200 (Al/Ti/C), 400 (Ti/Sb/Al), and 550 (Sn/SiO) during pointed spectroscopic observations. RAP observations are up to 20 times more sensitive than those in the EUVE all-sky survey. We present RAP observations of two dozen late-type stars. We derive surface fluxes from the Lexan/B and Al/Ti/C count rates and cataloged ROSAT Position Sensitive Proportional Counter (PSPC) data. The EUVE surface fluxes are reasonably correlated with surface fluxes calculated from PSPC measurements. The time variability of the sources has been examined. Most of the sources show no significant variability at the 99 percent confidence level. Flares were detected from the K7 V star Melotte 25 VA 334, the K3 V star V834 Tau (HD 29697), and the K3 + K8 Hyades binary BD +22669. The BD +22669 count rate at the peak of the flare is a factor of 6 higher than the quiescent count rate, with a peak Lexan/B luminosity of 7.9 1029 ergs/s. The V834 Tau flare was detected in both Lexan/B and Al/Ti/C bands. The peak luminosity of the flare is 1.6 1029 and 8 1028 ergs/s for Lexan/B and Al/Ti/C, respectively.

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