paper

Radio observations of the tidal disruption event XMMSL1 J074085

arXiv:1610.03861 · doi:10.3847/1538-4357/aa6192

Abstract

We present radio observations of the tidal disruption event candidate (TDE) XMMSL1 J074085 spanning 592 to 875 d post X-ray discovery. We detect radio emission that fades from an initial peak flux density at 1.6 GHz of mJy to mJy suggesting an association with the TDE. This makes XMMSL1 J074085 at Mpc the nearest TDE with detected radio emission to date and only the fifth TDE with radio emission overall. The observed radio luminosity rules out a powerful relativistic jet like that seen in the relativistic TDE Swift J1644+57. Instead we infer from an equipartition analysis that the radio emission most likely arises from a non-relativistic outflow similar to that seen in the nearby TDE ASASSN-14li, with a velocity of about km s and a kinetic energy of about erg, expanding into a medium with a density of about cm. Alternatively, the radio emission could arise from a weak initially-relativistic but decelerated jet with an energy of erg, or (for an extreme disruption geometry) from the unbound debris. The radio data for XMMSL1 J074085 continues to support the previous suggestion of a bimodal distribution of common non-relativistic isotropic outflows and rare relativistic jets in TDEs (in analogy with the relation between Type Ib/c supernovae and long-duration gamma-ray bursts). The radio data also provide a new measurement of the circumnuclear density on a sub-parsec scale around an extragalactic supermassive black hole.

arXiv commentAccepted to ApJ. One new figure and minor revisions added; conclusions unchanged

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