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Rebrightening of the Supersoft X-ray Transient in the M31 Globular Cluster Bol 194

ATEL # 1334; A.K.H. Kong (NTHU), R. Di Stefano (CfA)
on 17 Dec 2007; 13:43 UT
Password Certification: Albert Kong (

Subjects: X-ray, Transients

We report the two Swift follow-up observations of the supersoft X-ray transient in the M31 globular cluster Bol 194 (ATel #1296,#1306,#1328). The source was first detected with Chandra on 2007 Nov 3 (ATel #1328) and has been monitored with Swift and Chandra since then. Swift observations taken on 2007 Nov 24 indicate that the source is still active (ATel #1306). However, the source was not detected with Chandra on 2007 Nov 27 with a 95% upper limit of 2.5e35 erg/s (ATel #1328). The source was observed with Swift on 2007 Dec 2-3 and was clearly detected with a 4.7 ks observation. All the source photons are from below 0.8 keV and the 0.3-1 keV unabsorbed luminosity is 3.8e37 erg/s, assuming the same parameters used in Haberl et al. (2007; ATel #1306). However, the source was not detected in a 3.9 ks Swift observation taken on 2007 Dec 17. We derived a 95% upper limit of 2.6e37 erg/s.

We would like to thank the Swift team for the scheduling of the observations.

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