Discovery of Pulsed X-Ray Emission from the Small Magellanic Cloud Transient RX J0117.6–7330

Abstract

We report on the detection of pulsed, broadband, X-ray emission from the transient source RX J0117.6-7330. The pulse period of 22 s is detected by the ROSAT/PSPC instrument in a 1992 September 30-October 2 observation and by the Compton Gamma-Ray Observatory/BATSE instrument during the same epoch. Hard X-ray pulsations are detectable by BATSE for approximately 100 days surrounding the ROSAT observation (1992 August 28-December 8). The total directly measured X-ray luminosity during the ROSAT observation is 1.0 × 10^(38) (d/60 kpc)^2 ergs s^(-1). The pulse frequency increases rapidly during the outburst, with a peak spin-up rate of 1.2 × 10^(−10) Hz s^(-1) and a total frequency change of 1.8%. The pulsed percentage is 11.3% from 0.1-2.5 keV, increasing to at least 78% in the 20-70 keV band. These results establish RX J0117.6-7330 as a transient Be binary system.