First Detection of an X-Ray Burst and a One-Hour Intensity Dip in 4U1323-62

Abstract

We report the results of a 1.4 10⁴s observation of the region of 4U 1323-62 with the EXOSAT ME. The source has a flux of 7 8 10^-11 erg/cm²s (2 10 keV) and a power-law spectrum with 1.1 < α < 1.8. During our observation, the source showed a symmetric 60% dip in its X-ray flux of R~1 hr. The spectrum hardens during the dip. Inside the dip we observed an X-ray burst with a 2 10 keV peak flux of ∼7 10^-10 erg/cm²s. The burst spectrum is black-body, and shows evidence of cooling during the burst decay. The discovery of a burst from 4U 1323-62 settles the classification of the source; the observation of a dip suggests that we may be able to measure its orbital period in the near future.