Millisecond X-ray bursts from Circinus X-1

Abstract

X-ray bursts lasting less than 10 ms have been observed in the 1-8-keV flux from Cir X-1. The strongest burst shows structure at the 1-ms level. Thus far, millisecond variability in X-ray emission has been detected from only one other source: the black hole candidate Cyg X-1. The close similarity in the temporal profile of the emission from these objects suggests that Cir X-1 is also a black hole.