SRG/eROSITA prospects for the detection of stellar tidal disruption flares

We discuss the potential of the eROSITA telescope on board the Spectrum-RoentgenGamma (SRG) observatory to detect stellar tidal disruption events (TDE) during its 4-year all-sky survey. We propose to distinguish such events from other X-ray transients using two criteria: i) large (more than a factor of 10) X-ray variation between two subsequent 6-month scans of the sky and ii) soft X-ray spectrum. The expected number of TDE candidates is ∼ 103 per scan (with most of the events being new discoveries in a given scan), so that a total of several thousand TDE candidates can be found during the 4-year survey. The actual number may significantly differ from this estimate, since it is based on just a few TDEs observed so far. The eROSITA all-sky survey is expected to be nearly equally sensitive to TDEs occurring near supermassive black holes (SMBH) of mass between ∼ 106 and ∼ 10M⊙ and will thus provide a unique census of quiescent SMBHs and associated nuclear stellar cusps in the local Universe (z . 0.15). Information on TDE candidates will be available within a day after their detection and localization by eROSITA, making possible follow-up observations that may reveal peculiar types of TDEs.