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Late Time Multi-Wavelength Observations of SWIFT J1644+5734: A Luminous Optical/IR Bump and Quiescent X-Ray Emission

Levan, AJ and Tanvir, NR and Brown, GC and Metzger, BD and Page, KL and Cenko, SB and O'Brien, PT and Lyman, JD and Wiersema, K and Stanway, ER and Fruchter, AS and Perley, DA and Bloom, JS (2016) Late Time Multi-Wavelength Observations of SWIFT J1644+5734: A Luminous Optical/IR Bump and Quiescent X-Ray Emission. The Astrophysical Journal, 819 (51). ISSN 1538-4357

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Abstract

The American Astronomical Society. All rights reserved.We present late time multi-wavelength observations of Swift J1644+57, suggested to be a relativistic tidal disruption flare (TDF). Our observations extend to >4 years from discovery and show that 1.4 years after outburst the relativistic jet switched off on a timescale less than tens of days, corresponding to a power-law decay faster than t-70. Beyond this point weak X-rays continue to be detected at an approximately constant luminosity of LX ∼ 5 ×1042 erg s-1 and are marginally inconsistent with a continuing decay of t-5/3, similar to that seen prior to the switch-off. Host photometry enables us to infer a black hole mass of MBH = 3 ×106 Mo, consistent with the late time X-ray luminosity arising from sub-Eddington accretion onto the black hole in the form of either an unusually optically faint active galactic nucleus or a slowly varying phase of the transient. Optical/IR observations show a clear bump in the light curve at timescales of 30-50 days, with a peak magnitude (corrected for host galaxy extinction) of MR ∼ -22 to -23. The luminosity of the bump is significantly higher than seen in other, non-relativistic TDFs and does not match any re-brightening seen at X-ray or radio wavelengths. Its luminosity, light curve shape, and spectrum are broadly similar to those seen in superluminous supervnovae, although subject to large uncertainties in the correction of the significant host extinction. We discuss these observations in the context of both TDF and massive star origins for Swift J1644+5734 and other candidate relativistic tidal flares. © 2016.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical And Space Sciences, 0305 Organic Chemistry, 0306 Physical Chemistry (Incl. Structural)
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: American Astronomical Society
Date Deposited: 17 Feb 2017 12:27
Last Modified: 07 Sep 2017 13:08
DOI or Identification number: 10.3847/0004-637X/819/1/51
URI: http://researchonline.ljmu.ac.uk/id/eprint/5608

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