2017MNRAS.471.1141L -
Mon. Not. R. Astron. Soc., 471, 1141-1152 (2017/October-2)
Radiative interaction between the relativistic jet and optically thick envelope in tidal disruption events.
LU W., KROLIK J., CRUMLEY P. and KUMAR P.
Abstract (from CDS):
Reverberation observations yielding a lag spectrum have uncovered an Fe K α fluorescence line in the tidal disruption event (TDE) Swift J1644+57. The discovery paper used the lag spectrum to argue that the source of the X-ray continuum was located very close to the black hole (∼30 gravitational radii) and moved subrelativistically. We reanalyse the lag spectrum, pointing out that dilution effects cause it to indicate a geometric scale an order of magnitude larger than inferred by Kara et al. If the X-ray continuum is produced by a relativistic jet, as suggested by the rapid variability, high luminosity and hard spectrum, this larger scale predicts an Fe ionization state consistent with efficient K α photon production. Moreover, the momentum of the jet X-rays impinging on the surrounding accretion flow on this large scale accelerates a layer of gas to speeds ∼0.1-0.2c, consistent with the blueshifted line profile. Implications of our results on the global picture of jetted TDEs are discussed. A power-law γ/X-ray spectrum may be produced by external ultraviolet (UV)-optical photons being repetitively inverse-Compton scattered by cold electrons in the jet, although our model for the K α reverberation does not depend on the jet radiation mechanism (magnetic reconnection in a Poynting jet is still a viable mechanism). The non-relativistic wind driven by jet radiation may explain the late-time radio rebrightening in Swift J1644+57. This energy injection may also cause the thermal UV-optical emission from jetted TDEs to be systematically brighter than in non-jetted ones.
Abstract Copyright:
© 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
Journal keyword(s):
accretion, accretion discs - line: profiles - methods: analytical - galaxies: nuclei - radio continuum: transients - X-rays: bursts - X-rays: bursts
CDS comments:
Swift J1112.2+8238 is a misprint for Swift J1112.2-8238.
Simbad objects:
8
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