SDSS~J075217.84+193542.2: X-ray weighing of a secondary BH

This is the authors' abstract. We don't add key points for this paper.

Precise measurements of black hole (BHs) masses are necessary to understand the coevolution of these sources and their host galaxies. Sometimes in the center of a galaxy there is not one, but two BHs. The BH duality of the quasar nucleus SDSS~J075217.84+193542.2 (herein SDSS~J0752) was recently proposed based on the observed strict periodicity of optical emission from the source. We tested this assumption using X-ray observations with Swift/XRT (2008--2010). We fitted the SDSS~J075217 spectrum using a Comptonization model and discovered soft X-ray variability in the 0.3--10~keV energy range. We pursued a scenario in which two supermassive BHs at the center of SDSS~J0752 form a pair; and the less massive (secondary) BH periodically crosses/punctures the disk around the more massive (primary) BH. We associate these periodic crossings with tidal disruptions of the disk and, as a consequence, with an increase in X-rays seen as a flare in SDSS~J0752. During such an X-ray flare event (2008--2010), we discovered a change in the source spectral states and the photon index saturation at the Γ~3 level with mass accretion rate M. For BH mass scaling we used sources: OJ~287, M101 ULX--1 and HLX--1 ESO~243--49, as a reference ones, and found that MSDSS=9× 10⁷ solar masses, assuming dSDSS= 500 Mpc. Thus, we obtained a lower limit to a BH mass due the unknown inclination. In addition, we used the virial mass of the secondary BH based on H_α-line measurements and we estimated the binary's inclination at SDSS~J0752, i=80∘, using a scaling technique.