paper

iPTF16fnl: a faint and fast tidal disruption event in an E+A galaxy

arXiv:1703.00965 · doi:10.3847/1538-4357/aa7579

Abstract

We present ground-based and \textit{Swift} observations of iPTF16fnl, a likely tidal disruption event (TDE) discovered by the intermediate Palomar Transient Factory (iPTF) survey at 66.6 Mpc. The lightcurve of the object peaked at absolute mag. The maximum bolometric luminosity (from optical and UV) was erg/s, an order of magnitude fainter than any other optical TDE discovered so far. The luminosity in the first 60 days is consistent with an exponential decay, with , where =~57631.0 (MJD) and days. The X-ray shows a marginal detection at erg/s (\textit{Swift} X-ray Telescope). No radio counterpart was detected down to 3, providing upper limits for monochromatic radio luminosity of erg/s and erg/s (VLA, 6.1 and 22 GHz). The blackbody temperature, obtained from combined \textit{Swift} UV and optical photometry, shows a constant value of 19,000 K. The transient spectrum at peak is characterized by broad He II and H emission lines, with an FWHM of about 14,000 km/s and 10,000 km/s respectively. He I lines are also detected at 5875 and 6678. The spectrum of the host is dominated by strong Balmer absorption lines, which are consistent with a post-starburst (E+A) galaxy with an age of 650 Myr and solar metallicity. The characteristics of iPTF16fnl make it an outlier on both luminosity and decay timescales, as compared to other optically selected TDEs. The discovery of such a faint optical event suggests a higher rate of tidal disruptions, as low luminosity events may have gone unnoticed in previous searches.

arXiv comment14 pages, 11 figures, accepted for publication in ApJ

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