Revealing the Nature of Extreme Coronal-line Emitter SDSS
  J095209.56+214313.3
  Extreme coronal-line emitter (ECLE) SDSSJ095209.56+214313.3, known by its
strong, fading, high ionization lines, has been a long standing candidate for a
tidal disruption event, however a supernova origin has not yet been ruled out.
Here we add several new pieces of information to the puzzle of the nature of
the transient that powered its variable coronal lines: 1) an optical light
curve from the Lincoln Near Earth Asteroid Research (LINEAR) survey that
serendipitously catches the optical flare, and 2) late-time observations of the
host galaxy with the Swift Ultraviolet and Optical Telescope (UVOT) and X-ray
telescope (XRT) and the ground-based Mercator telescope. The well-sampled,
$\sim10$-year long, unfiltered LINEAR light curve constrains the onset of the
flare to a precision of $\pm5$ days and enables us to place a lower limit on
the peak optical magnitude. Difference imaging allows us to estimate the
location of the flare in proximity of the host galaxy core. Comparison of the
\textsl{GALEX} data (early 2006) with the recently acquired Swift UVOT (June
2015) and Mercator observations (April 2015) demonstrate a decrease in the UV
flux over a $\sim 10$ year period, confirming that the flare was UV-bright. The
long-lived UV-bright emission, detected 1.8 rest-frame years after the start of
the flare, strongly disfavors a SN origin. These new data allow us to conclude
that the flare was indeed powered by the tidal disruption of a star by a
supermassive black hole and that TDEs are in fact capable of powering the
enigmatic class of ECLEs.
