New X-ray Outburst of ESO 243-49 HLX-1
ATel #3564; A. K.H. Kong (NTHU/HKU)
on 17 Aug 2011; 10:37 UT
Credential Certification: Albert Kong (akong@phys.nthu.edu.tw)
Subjects: X-ray, Black Hole, Variables
We report on recent Swift/XRT observations of the hyper-luminous X-ray source, HLX-1, in the galaxy ESO 243-49 (Farrell et al. 2009). Swift/XRT has been performing regular monitoring observations of HLX-1 since late-2008 and it is suggestive that the source has an outburst cycle of 373 days (see Kong 2011, arXiv:1102.3212; Lasota et al. 2011). The last X-ray outburst occurred in 2010 late-August (ATel #2821). Since 2011-08-15, HLX-1 has brightened again with an average 0.3-10 keV count rate of 0.03 c/s in the last 3 days which is consistent with the initial phase of previous outbursts. Furthermore, the source appears to be softer in X-ray colors for which all photons are from < 1.5 keV. Based on the observations, we suggest that the recurrence time of ~370 days is real and it is likely orbital in origin (Lasota et al. 2011).
Multiwavelength follow-up observations are encouraged.