RADIO MONITORING OF THE TIDAL DISRUPTION EVENT SWIFT J164449.3+573451. II. THE RELATIVISTIC JET SHUTS OFF AND A TRANSITION TO FORWARD SHOCK X-RAY/RADIO EMISSION
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Mullard Radio Observatory, Cavendish Laboratory, Cambridge, CB3 0HE (United Kingdom)
- Racah Institute of Physics, Hebrew University, 91904 Jerusalem (Israel)
- Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany)
- Department of Physics and Astronomy, York University, Toronto, Ontario (Canada)
We present continued multi-frequency radio observations of the relativistic tidal disruption event Swift J164449.3+573451 (Sw 1644+57) extending to t Almost-Equal-To 600 days. The data were obtained with the JVLA and AMI Large Array as part of our on-going study of the jet energetics and the density structure of the parsec-scale environment around the disrupting supermassive black hole. We combine these data with public Swift/XRT and Chandra X-ray observations over the same time-frame to show that the jet has undergone a dramatic transition starting at Almost-Equal-To 500 days, with a sharp decline in the X-ray flux by about a factor of 170 on a timescale of {delta}t/t {approx}< 0.2 (and by a factor of 15 in {delta}t/t Almost-Equal-To 0.05). The rapid decline rules out a forward shock origin (direct or reprocessing) for the X-ray emission at {approx}< 500 days, and instead points to internal dissipation in the inner jet. On the other hand, our radio data uniquely demonstrate that the low X-ray flux measured by Chandra at Almost-Equal-To 610 days is consistent with emission from the forward shock. Furthermore, the Chandra data are inconsistent with thermal emission from the accretion disk itself since the expected temperature of {approx}30-60 eV and inner radius of {approx}2-10 R{sub s} cannot accommodate the observed flux level or the detected emission at {approx}> 1 keV. We associate the rapid decline with a turn off of the relativistic jet when the mass accretion rate dropped below {approx} M-dot{sub Edd}{approx}0.006 M{sub Sun} yr{sup -1} (for a 3 Multiplication-Sign 10{sup 6} M{sub Sun} black hole and order unity efficiency) indicating that the peak accretion rate was about 330 M-dot{sub Edd}, and the total accreted mass by t Almost-Equal-To 500 days is about 0.15 M{sub Sun }. From the radio data we further find significant flattening in the integrated energy of the forward shock at t {approx}> 250 days with E{sub j,iso} Almost-Equal-To 2 Multiplication-Sign 10{sup 54} erg (E{sub j} Almost-Equal-To 10{sup 52} erg for a jet opening angle, {theta}{sub j} = 0.1) following a rise by about a factor of 15 at Almost-Equal-To 30-250 days. Projecting forward, we predict that the emission in the radio and X-ray bands will evolve in tandem with similar decline rates.
- OSTI ID:
- 22126869
- Journal Information:
- Astrophysical Journal, Vol. 767, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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