ASASSN-15oi: A Rapidly Evolving, Luminous Tidal Disruption Event at 216 Mpc

Holoien, TW-S, Kochanek, CS, Prieto, JL, Grupe, D, Chen, P, Godoy-Rivera, D, Stanek, KZ, Shappee, BJ, Dong, S, Brown, JS, Basu, U, Beacom, JF, Bersier, D, Brimacombe, J, Carlson, EK, Falco, E, Johnston, E, Madore, BF, Pojmanski, G and Seibert, M (2016) ASASSN-15oi: A Rapidly Evolving, Luminous Tidal Disruption Event at 216 Mpc. Monthly Notices of the Royal Astronomical Society, 463 (4). pp. 3813-3828. ISSN 0035-8711

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Abstract

We present ground-based and Swift photometric and spectroscopic observations of the tidal disruption event (TDE) ASASSN-15oi, discovered at the center of 2MASX J20390918-3045201 ($d\simeq216$ Mpc) by the All-Sky Automated Survey for SuperNovae (ASAS-SN). The source peaked at a bolometric luminosity of $L\simeq1.9\times10^{44}$ ergs s$^{-1}$ and radiated a total energy of $E\simeq5.0\times10^{50}$ ergs over the $\sim3.5$ months of observations. The early optical/UV emission of the source can be fit by a blackbody with temperature increasing from $T\sim2\times10^4$ K to $T\sim6\times10^4$ K while the luminosity declines from $L\simeq1.9\times10^{44}$ ergs s$^{-1}$ to $L\simeq2.8\times10^{43}$ ergs s$^{-1}$, requiring the photosphere to be shrinking rapidly. The optical/UV luminosity decline is broadly consistent with an exponential decline, $L\propto e^{-t/t_0}$, with $t_0\simeq35$ days. ASASSN-15oi also exhibits roughly constant soft X-ray emission that is significantly weaker than the optical/UV emission. Spectra of the source show broad helium emission lines and strong blue continuum emission in early epochs, although these features fade rapidly and are not present $\sim3$ months after discovery. The early spectroscopic features and color evolution of ASASSN-15oi are consistent with a TDE, but the rapid spectral evolution is unique among optically-selected TDEs.

Item Type:	Article
Additional Information:	This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record "ASASSN-15oi: A Rapidly Evolving, Luminous Tidal Disruption Event at 216 Mpc" is available online at http://dx.doi.org/10.1093/mnras/stw2272
Uncontrolled Keywords:	astro-ph.HE; astro-ph.HE
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	Oxford University Press
Related URLs:	http://arxiv.org/abs/1602.01088v1
Date of acceptance:	6 September 2016
Date of first compliant Open Access:	10 February 2016
Date Deposited:	10 Feb 2016 10:24
Last Modified:	20 Apr 2022 09:27
DOI or ID number:	10.1093/mnras/stw2272
URI:	https://researchonline.ljmu.ac.uk/id/eprint/2897

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