Abstract
In March 2011 Swift detected an extremely luminous and long-lived outburst from the nucleus of an otherwise quiescent, low luminosity (LMC-like) galaxy. Named Swift J1644+57, its combination of high-energy luminosity (1048 ergs s−1 at peak), rapid X-ray variability (factors of >100 on timescales of 100 seconds) and luminous, rising radio emission suggested that we were witnessing the birth of a moderately relativistic jet (Γ ∼ 2 − 5), created when a star is tidally disrupted by the supermassive black hole in the centre of the galaxy. A second event, Swift J2058+0516, detected two months later, with broadly similar properties lends further weight to this interpretation. Taken together this suggests that a fraction of tidal disruption events do indeed create relativistic outflows, demonstrates their detectability, and also implies that low mass galaxies can host massive black holes. Here, I briefly outline the observational properties of these relativistic tidal flares observed last year, and their evolution over the first year since their discovery.
Highlights
On the 28th March 2011 the Swift satellite detected what appeared at first to be a very long duration gamma-ray burst (GRB 110328A), detected as an image trigger with a duration of over twenty minutes [1]
An analysis of archival images of the field revealed a quiescent counterpart with R ∼ 22 in the X-ray error box [3]
Combined with the luminous X-ray afterglow these properties appeared at first sight similar to those of the Supergiant Fast X-ray Transients – High mass X-ray binaries with our Galaxy [4]
Summary
On the 28th March 2011 the Swift satellite detected what appeared at first to be a very long duration gamma-ray burst (GRB 110328A), detected as an image trigger with a duration of over twenty minutes [1]. Our observations unveiled a faint, fading infrared counterpart [6], which would provide a precise position for the burst relative to this host galaxy [7]. The X-ray afterglow was seen to persist at a bright level (>10−10 ergs s−1 cm−2) for several days, and subsequently re-triggered the BAT on two further occasions (i.e. triggered it four times in total) [2].
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