http://arxiv.org/abs/1802.02151
Recent optical/UV transient surveys have been successful in finding tidal disruption events (TDEs), where a star is disrupted by the tidal gravity of a supermassive black hole. For the majority of the TDE candidates, the observed energy in the optical/UV bands is only ~10^{51} erg. We show that this observed energy is smaller than the theoretically expected minimum bolometric energy by a factor of 10 to 100. We argue that this discrepancy is because the majority of the energy release is in the extreme-UV (EUV) band and/or in the form of relativistic jets beamed away from the Earth. The EUV scenario is supported by existing mid-infrared data and should be further tested by future dust reverberation observations. The jet scenario is disfavored by the radio observations of ASASSN-14li but may still be viable for other TDE candidates. We also provide evidences that most of the missing energy, in the EUV and/or in the form of jets, is released on a timescale comparable to the orbital period of the most tightly bound material P_{min}, which means: (1) the circularization of the fall-back stream may occur rapidly (within ~P_{min} after the initial stream self-intersection), and (2) the luminosity of the accretion flow or the jet power may not be capped near the Eddington level when the fall-back rate is super-Eddington.
W. Lu and P. Kumar
Thu, 8 Feb 18
33/43
Comments: 9 pages, 3 figures, submitted to MNRAS, comments welcome!
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