LATE TIME MULTI-WAVELENGTH OBSERVATIONS OF SWIFT J1644+5734: A LUMINOUS OPTICAL/IR BUMP AND QUIESCENT X-RAY EMISSION
- Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom)
- Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH (United Kingdom)
- Columbia Astrophysics Laboratory, New York, NY 10027 (United States)
- Astrophysics Science Division, NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, MD 20771 (United States)
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
- Department of Astronomy, California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States)
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{sup −70}. Beyond this point weak X-rays continue to be detected at an approximately constant luminosity of L{sub X} ∼ 5 × 10{sup 42} erg s{sup −1} and are marginally inconsistent with a continuing decay of t{sup −5/3}, similar to that seen prior to the switch-off. Host photometry enables us to infer a black hole mass of M{sub BH} = 3 × 10{sup 6} M{sub ⊙}, 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 M{sub R} ∼ −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.
- OSTI ID:
- 22521479
- Journal Information:
- Astrophysical Journal, Vol. 819, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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