[1111.2802] Jets from Tidal Disruptions of Stars by Black Holes

Authors: Julian H. Krolik, Tsvi Piran

Date: 11 Nov 2011

Abstract: Tidal disruption of main sequence stars by black holes has generally been thought to lead to a signal dominated by UV emission. If, however, the black hole spins rapidly and the poloidal magnetic field intensity on the black hole horizon is comparable to the inner accretion disk pressure, a powerful jet may form whose luminosity can easily exceed the thermal UV luminosity. When the jet beam points at Earth, its non-thermal luminosity can dominate the emitted spectrum. The thermal and non-thermal components decay differently with time. In particular, the thermal emission should remain roughly constant for a significant time after the period of maximum accretion, beginning to diminish only after a delay, whereas after the peak accretion rate, the non-thermal jet emission decays, but then reaches a plateau. When the newly-found flare source Swift J2058 is analyzed in terms of this model, it is found to be consistent with an event in which a main sequence solar-type star is disrupted by a black hole of mass at least $\sim 10ˆ7 M_{\odot}$. Swift may have already observed the beginning of the flat phase in the non-thermal emission from this source. Optical photometry over the first $\simeq 40$ d of this flare is also consistent with this picture, but there is a large uncertainty in the bolometric correction. We suggest that future searches for main sequence tidal disruptions use methods sensitive to jet radiation as well as to thermal UV radiation.

abs pdf

Nov 14, 2011

1111.2802 (/preprints)
2011-11-14, 08:27 [edit]


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