SRG/eROSITA detection of the tidal disruption event AT2022dsb
ATel #15259; Zhu Liu, Adam Malyali, Arne Rau, Andrea Merloni (all MPE), Mirko Krumpe (AIP)
on 3 Mar 2022; 17:01 UT
Credential Certification: Zhu Liu (liuzhu@mpe.mpg.de)
Subjects: X-ray, Tidal Disruption Event
Referred to by ATel #: 15293
We report on the X-ray detection from SRG/eROSITA (Predehl et al. A&A 647, A1, 2021) of the tidal disruption event (TDE) AT2022dsb. AT2022dsb was reported as a new optical transient ASASSN-22cs on 2022 March 1st, (TNS Astronomical Transient Report No. 138375), and was spectroscopically classified as a TDE at a redshift of z=0.023 by ePESSTO+ (TNS Classification Report No. 12024).
AT2022dsb was in the Field-of-View of eROSITA during the fifth consecutive all-sky survey (eRASS5) on 2022 February 17th, 11 days before the ASASSN TNS report. The source was discovered as a new soft X-ray nuclear transient eRASSt J154221.7-224013.0 in eRASS5 with a total exposure time of ~239s and total photon counts of 36 in the 0.2-2.3keV energy band. An optical spectrum was obtained with the FLOYDS spectrograph mounted at the LCOGT 2m telescope at Haleakala Observatory on February 26th. In agreement with the TNS Classification Report (No. 12024), the spectrum shows broad Halpha and prominent HeII 4685 in emission.
Assuming an absorbed blackbody model, with equivalent hydrogen column density fixed to N_H=1.7x10^21 cm^-2 (Willingale et al., 2013, MNRAS, 431, 394), we derived a best-fitting blackbody temperature of 45+-10eV with observed 0.2-2.3keV flux of 3.3+-1.1E-13 erg/s/cm^2 (~4.2E41 erg/s). AT2022dsb was not detected in all four previous eROSITA all-sky surveys. Using the best-fitting model from eRASS5, we derived a 3 sigma 0.2-2.3keV flux upper limit of 5.0E-14 erg/s/cm^2 combing all the previous four eRASS data which has a total exposure of 978s. Additional XMM, NICER and Swift observations have been requested to continue monitoring the X-ray/ UV evolution of this TDE candidate.
