AB DOR - A SINGLE STAR WITH RSCVN LIKE, ACTIVITY IN X-RAY-BAND

Using the archival ROSAT PSPC observations, AB Dor is found to be vari able in X-rays. The periodic variations are consistent with previously reported rotational period of 0(d).514. The average spectrum of AB Do r is best represented with two-temperature Raymond-Smith model with kT values of 0.19 +/- 0.07 and 1.17 +/- 0.02 keV. The quiescent luminosi ty of the system is found to be 4.36 +/- 0.6 x 10(30) ergs s(-1). A fl are with a rise time of similar to 350 seconds is detected during whic h X-ray luminosity rises from 5.8 +/- 1.6 x 10(30) to 15.8 +/- 4.9 x 1 0(30) ergs s(-1). We conclude that AB Dor is very similar to the activ e components of RS CVn binaries and other active classes. In view of t he wide separation from the binary companion Rst 137B, this activity m ust be intrinsic to the active star.