Birth of a relativistic outflow in the unusual [gamma]-ray transient Swift J164449.3+573451

• Published in: Nature (London) Vol. 476; no. 7361; p. 425
• Main Authors: Zauderer, B A, Berger, E, Soderberg, A M, Loeb, A, Narayan, R, Frail, D A, Petitpas, G R, Brunthaler, A, Chornock, R, Carpenter, J M, Pooley, G G, Mooley, K, Kulkarni, S R, Margutti, R, Fox, D B, Nakar, E, Patel, N A, Volgenau, N H, Culverhouse, T L, Bietenholz, M F, Rupen, M P, Max-Moerbeck, W, Readhead, A C S, Richards, J, Shepherd, M, Storm, S, Hull, C L H
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group 25.08.2011
• ISSN: 0028-0836; 1476-4687

Active galactic nuclei, which are powered by long-term accretion onto central supermassive black holes, produce relativistic jets with lifetimes of at least one million years, and the observation of the birth of such a jet is therefore unlikely. Transient accretion onto a supermassive black hole, for example through the tidal disruption of a stray star, thus offers a rare opportunity to study the birth of a relativistic jet. On 25 March 2011, an unusual transient source (Swift J164449.31573451) was found, potentially representing such an accretion event. Here we report observations spanning centimetre to millimetre wavelengths and covering the first month of evolution of a luminous radio transient associated with Swift J164449.31573451. The radio transient coincides with the nucleus of an inactive galaxy. We conclude that we are seeing a newly formed relativistic outflow, launched by transient accretion onto a million-solar-mass black hole. A relativistic outflow is not predicted in this situation, but we show that the tidal disruption of a star naturally explains the observed high-energy properties and radio luminosity and the inferred rate of such events. The weaker beaming in the radio-frequency spectrum relative to γ-rays or X-rays suggests that radio searches may uncover similar events out to redshifts of z [asymptotically =] 6. [PUBLICATION ABSTRACT]