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OJ 287 at its highest X-ray state since the beginning of Swift monitoring

ATel #10043; Dirk Grupe (Morehead State University), S. Komossa (QianNan Normal University for Nationalities), & Abe Falcone (Penn State University)
on 3 Feb 2017; 02:10 UT
Credential Certification: Dirk Grupe (dgrupe007@gmail.com)

Subjects: Optical, Ultra-Violet, X-ray, Black Hole, Blazar

We report on an outburst of the 0.3-10 keV X-ray emission of the blazar OJ 287, which is a candidate binary black hole system. This outburst occurred on 2017 February 02, during observations at approximately 08:52 UT (MJD 57786.369975). Swift previously discovered OJ 287 in a bright X-ray and UV state on 2016 October 12 (Grupe et al., ATEL 9629). We have followed OJ 287 since October 2016 with a two day cadence. Although it remained bright, its X-ray flux seemed to suggest an end of the flaring state. However, about a week ago OJ 287 started to become brighter again in X-rays. Further observations were triggered last night, which resulted in the detection of an outburst at a level of 2 counts/s, the highest count rate seen since the start of the monitoring program by Swift in 2005 May. The 0.3-10 keV spectrum of the current outburst can be fitted by a single power law model with a photon index of Gamma = 2.62+/-0.06. The observed flux in the 0.3-10 keV band currently is (3.83+/-0.10)e-14 W m-2 (or e-11 ergs/s/cm2). In the optical and UV band, OJ 287 has become brighter compared with the observation during the last few weeks. The optical and UV magnitudes found in the most recent observation from February 02 are (not corrected for Galactic reddening): V: 14.09+/-0.04, B: 14.43+/-0.04, U: 13.56+/-0.05 UVW1: 13.53+/-0.05, UVM2: 13.48+/-0.05, UVW2: 13.66+/-0.05. We are planning to continue monitoring OJ 287 with Swift and encourage observers to obtain multi-wavelength observations in order to cover this brightest X-ray outburst since 2005.