DISCOVERY OF PERIODIC ECLIPSES IN THE X-RAY PULSAR 1H 0253+193

Periodic intensity dips with a period of 21,829 s were discovered in the X-ray light curve of the 206 s pulsar 1H 0253 + 193. The X-ray flux outside of the dips was 2 x 10(-11) ergs cm-2 s-1 (in the 2-10 keV energy band), while the X-ray flux during the dips was below the detection limit of 2 x 10(-12) ergs cm-2 s-1. The duration of the intensity dips and the transient time from normal to intensity dip (or vice versa) were 1990 and 50 s, respectively. The periodic dips indicate that the X-ray pulsar 1H 0253 + 193 is an X-ray binary source, and the dips are naturally explained by an eclipse by the companion star. We have estimated the stellar radii of the binary system and the orbital separation. We conclude that the system is a DQ Her-type cataclysmic variable.