%0 Journal Article
%T Swift J164449.3+573451 and Swift J2058.4+0516: Black hole mass estimates for tidal disruption event sources
%A Elena Seifina
%A Enrico Virgilli
%A Lev Titarchuk
%J -
%D 2017
%R 10.1051/0004-6361/201730869
%X A tidal disruption event (TDE) is an astronomical phenomenon in which a previously dormant black hole (BH) destroys a star passing too close to its central part. We analyzed the flaring episode detected from the TDE sources, <i>Swift<i/>ˋJ164449.3+573451 and <i>Swift<i/>ˋJ2058.4+0516 (hereafter <i>Swift<i/> J1644+57 and <i>Swift <i/>J2058+05, respectively) using RXTE, <i>Swift <i/>and <i>Suzaku <i/>data. The spectra are well fitted by the so called Bulk Motion Comptonization model for which the best-fit photon index 忙 varies from 1.1 to 1.8. We have firmly established the saturation of the photon index versus mass accretion rate at 忙<sub>sat<sub/> about 1.7每1.8. The saturation of 忙 is usually identified as a signature of a BH now established in <i>Swift<i/> J1644+57 and <i>Swift <i/>J2058+05. In <i>Swift<i/> J1644+57 we found the relatively low 忙<sub>sat<sub/> values which indicate a high electron (plasma) temperature, <i>k<i/><i>T<i/><sub>e<sub/> ~ 30每40 keV. This is also consistent with high cutoff energies, <i>E<i/><sub>cut<sub/> ~ 60每80 keV found using best fits of the RXTE spectra. <i>Swift<i/> J2058+05 shows a lower electron temperature, <i>k<i/><i>T<i/><sub>e<sub/> ~ 4每10 keV than that for <i>Swift<i/> J1644+57. For the BH mass estimate we used the scaling technique taking the Galactic BHs, GRO J1655每40,GX 339每4, Cyg X每1 and 4U 1543每47as reference sources and found that the BH mass in <i>Swift<i/> J1644+57 is <i>M<i/><sub>BH<sub/> ≡ 7 ℅ 10<sup>6<sup/><i>M<i/><sub>×<sub/> assuming the distance to this source of 1.5 Gpc. For <i>Swift<i/> J2058+05 we obtain <i>M<i/><sub>BH<sub/> ≡ 2 ℅ 10<sup>7<sup/><i>M<i/><sub>×<sub/> assuming the distance to this source of 3.7 Gpc. We have also found that the seed (disk) photon temperatures are quite low, of order of 100每400 eV, in both of the sources, which are consistent with the estimated BH masses
%U https://www.aanda.org/articles/aa/full_html/2017/11/aa30869-17/aa30869-17.html