The discovery of X-ray bursts from CIR X-1.

Abstract

A sequence of eight X-ray flares was detected during an EXOSAT observation of the low-state Circinus X-1 (= BR Cir). The authors identify these flares with X-ray bursts from Cir X-1. The recurrence time, ratio of persistent flux to the time-averaged flux and indications of cooling during the bursts are all consistent with these bursts being type I, although the authors cannot rule out the possibility that the bursts are type II. Type I bursts would be strong evidence that Cir X-1 is a neutron star and not a black hole.