SRGe J131014.2+444315 - a tidal disruption event at early phase
ATel #14800; M. Gilfanov (IKI, MPA), S. Sazonov (IKI), P. Medvedev (IKI), G. Khorunzhev (IKI), R. Sunyaev (IKI, MPA), Y. Yao (Caltech), S. R. Kulkarni (Caltech), Y. Sharma (Caltech)
on 20 Jul 2021; 08:29 UT
Credential Certification: Marat Gilfanov (gilfanov@iki.rssi.ru)
Subjects: Optical, X-ray, Tidal Disruption Event
On June 6-7, 2021, in the course of its third all-sky survey, SRG/eROSITA discovered a new X-ray source SRGe J131014.2+444315 with a very soft spectrum with the blackbody temperature of 50+/-10 eV and the 0.3-2 keV flux of ~3.8e-13 erg/s/cm^2. The source was not detected during two previous scans of this region 6 and 12 months earlier, with an upper limit of ~1/20 of its current flux.
On July 6, the source was observed with Keck/LRIS, which shown narrow galaxy lines at z=0.199 on top of a blue continuum, and a broad emission complex around He II 4686A. The Keck spectrum is reminiscent of helium-rich tidal disruption events that are bright in UV/optical. ATLAS forced photometry data showed that optical brightening of the source started at some time between June 15 and June 27, roughly 1â2 weeks after the discovery of the X-rays source.
Swift XRT observations on July 13 and 17 revealed that the source continued its rise in X-rays and reached the level of 7.2e-13 erg/s/cm2, with a consistently soft spectrum, kTbb=64+/-6 eV. UVOT observations suggest that this object is bright in the UV (absolute magnitude in UVW2=-20.4).
Remarkably, this is the first event among optically active SRG/eROSITA TDEs, which was detected in X-rays before any optical activity was identified, suggesting that it was caught at early phase. Swift will continue monitoring of the source, follow-up visits with Keck are also planned. Further observations of the source at various wavelengths are of importance.
