The 2017 X-ray detection of the luminous nuclear transient AT 2017gbl

ATel #13435; Sasha Bates, Sol Gutierrez-lara (Commonwealth School, Boston), Jeremy J. Drake, Antonella Fruscione (Smithsonian Astrophysical Observatory)
on 31 Jan 2020; 23:37 UT
Credential Certification: Jeremy J. Drake (jdrake@cfa.harvard.edu)

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We report on a 2017 X-ray detection of the luminous nuclear transient AT 2017gbl (23:46:05.5, +53:14:01) made by the Chandra X-ray Observatory on 2017-11-03. AT 2017gbl was discovered in the near-infrared on MJD 57942.56 by Kool et al. (ATel #10651) superimposed on the nucleus of the luminous infrared galaxy IRAS 23436+5257 (D=146 Mpc). The transient was subsequently detected at 15.5 GHz (ATel #10679) and at 4.4 and 7.6 GHz (ATel #10712). AT 2017gbl was observed by the ACIS-S detector for 10 ks. A source was detected at the position of AT 2017gbl and appeared moderately extended with source counts spread over a region approximately 20 arcsec across. We extracted the counts around the source position within a circle of 13” radius. The background counts were estimated in an annulus around the source position with no contaminating sources. We measured a count rate of 8.6+/-1.3 count/ks in the [0.5-7 keV] energy range. The source was significantly variable during the observation at a level of approximately 40% over several ks. We extracted the spectrum and fitted it with both power law and MEKAL optically-thin plasma models absorbed by the interstellar medium. The MEKAL temperature and power law slope were not strongly constrained but the best-fits were approximately 80 keV and Gamma=0.8, respectively. The X-ray flux in the 0.5-7 keV bandpass was (1.04+/-0.2)e-13 erg/cm^2/s.