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A new outburst of ESO 243-49 HLX-1 after being in quiescence for two years

ATel #10289; Zhen Yan, Wenfei Yu (Shanghai Astronomical Observatory)
on 20 Apr 2017; 03:41 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Wenfei Yu (wenfei@shao.ac.cn)

Subjects: X-ray, Black Hole, Transient

We report on the most recent Swift observation of the hyper-luminous source ESO 243-49 HLX-1 taken on 2017-04-19 UT06:40:57. The XRT observation was taken in photon counting mode with an exposure time of 1753 seconds. The XRT count rate was 1.14+-0.27 e-2 c/s, indicating clearly that HLX-1 has entered a new outburst. We fitted the XRT spectrum with an absorbed power-law model with a fixed column density of 5e20 cm^-2. The power-law index is 4.4+-1.7 and the unabsorbed 0.3-10 keV luminosity is 9.8e41 erg/s, assuming a distance of 95 Mpc. If we use an absorbed disk blackbody model to fit the XRT spectrum, the inner disk temperature is about 0.13 keV and the unabsorbed 0.3-10 keV luminosity is 7.1e41 erg/s. The results are roughly consistent with those in previous outbursts (see ATel #3564, 4332, 5439, 6916).

The source has been in quiescence for more than 700 days since the previous outburst. The waiting time of this outburst is roughly two times longer than that of the previous outburst, which supports the conclusion that its outburst waiting time was getting longer (Yan et al. 2015, ApJ, 811, 23). We encourage multi-wavelength follow-up observations of the source during the new outburst.