Lightcurve Evolution of the nearest Tidal Disruption Event: A late-time,
  radio-only flare
  Tidal disruption events (TDEs) occur when a star passes close enough to a
galaxy's supermassive black hole to be disrupted by tidal forces. We discuss
new observations of IGRJ12580+0134, a TDE observed in NGC 4845 (d=17 Mpc) in
November 2010, with the Karl G. Jansky Very Large Array (JVLA). We also discuss
a reanalysis of 2010-2011 Swift and XMM-Newton observations, as well as new,
late-time Swift observations. Our JVLA observations show a decay of the nuclear
radio flux until 2015, when a plateau was seen, and then a significant (~factor
3) radio flare during 2016. The 2016 radio flare was also accompanied by radio
spectral changes, but was not seen in the X-rays. We model the flare as
resulting from the interaction of the nuclear jet with a cloud in the
interstellar medium. This is distinct from late-time X-ray flares in a few
other TDEs where changes in the accretion state and/or a fallback event were
suggested, neither of which appears possible in this case. Our reanalysis of
the Swift and XMM-Newton data from 2011 shows significant evidence for thermal
emission from a disk, as well as a very soft power-law. This, in addition to
the extreme X-ray flux increase seen in 2010 (a factor of >$100) bolsters the
identification of IGRJ12580+0134 as a TDE, not an unusual AGN variability
event.
