Revealing the Nature of Extreme Coronal-line Emitter SDSS J095209.56+214313.3

TL;DR

This study investigates the nature of the extreme coronal-line emitter SDSSJ095209.56+214313.3, providing evidence that its transient flare was caused by a tidal disruption event rather than a supernova, through multi-wavelength observations over a decade.

Contribution

The paper presents a comprehensive, multi-year observational analysis confirming the tidal disruption event origin of the ECLE, clarifying its powering mechanism and ruling out supernova scenarios.

Findings

The optical flare was precisely timed within a 10-year light curve.

UV flux decreased over 10 years, indicating a long-lived UV-bright phase.

Data supports TDE as the cause of the ECLE, not a supernova.

Abstract

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.