The Astrophysical Journal, 513:L53L56, 1999 March 1
1999. The American Astronomical Society. All rights reserved. Printed in U.S.A.
IMPLICATIONS FROM EXTREME-ULTRAVIOLET OBSERVATIONS FOR CORONAL HEATING OF ACTIVE STARS
and Manuel Gu¨del1
Paul Scherrer Institute, Wu¨renlingen and Villigen, 5232 Villigen PSI, Switzerland; firstname.lastname@example.org, email@example.com
Edward F. Guinan
Department of Astronomy and Astrophysics, Villanova University, Villanova, PA 19085; firstname.lastname@example.org
Received 1998 November 20; accepted 1998 December 28; published 1999 January 25
Extreme Ultraviolet Explorer (EUVE) data of two active solar analogs, 47 Cas and EK Dra, were used to
investigate flare statistics and the distribution of the flare occurrence rate in energy. The EUVE satellite observed
each star for almost 7 days. Simultaneous spectral data from its spectrometers were used to derive temperature
and abundance characteristics of their coronae. The emission models were derived from differential emission
measure distributions by fitting optically thin thermal models to the spectra. The Deep Survey instrument photon
lists were analyzed by applying different time binnings. A total of 28 flares were identified for further analysis.
The timing study provided estimates for the total radiative energy loss of each flare. The differential distribution
of flares in total X-ray energy is found to be a power law ( , with ) valid in the energya