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GCN Circular 15253

GRB 130925A: Initial Similarities to Swift J1644+57
2013-09-25T14:59:41Z (11 years ago)
S. Bradley Cenko at Caltech <>
D. N. Burrows (PSU), D. Malesani (DARK/NBI), A. Y. Lien (NASA/GSFC/ORAU),
S. B. Cenko (NASA/GSFC), and N. Gehrels (NASA/GSFC) report:

At 04:11:24 UT on 25 September 2013, the Swift BAT triggered on an object
denoted as GRB 130925A on the assumption that it is a gamma-ray burst
(Lien et al., GCN 15246).  Here we note that this source presents several
unusual features that are atypical of GRBs.

The initial XRT observations show extremely rapid and dramatic flaring
over the first 10^4 s, far in excess of what we typically see in GRBs.
The high X-ray flux at these relatively late times is likely what resulted
in the detection of this source by MAXI ~ 1 hour after the GRB (Suzuki
et al., GCN 15248).  The Swift/XRT light curve is available at the
following URL:

We note that this behavior is at first glance similar to the highly
variable soft X-ray light curve observed from Swift J1644+57 (GRB
110328A), which has been interpreted as a newly formed relativistic jet
resulting from the tidal disruption of a star by a super-massive black
hole (Burrows et al. 2011; Levan et al. 2011; Zauderer et al. 2011; Bloom
et al. 2011).  Like Swift J1644+57, GRB 130925A is a BAT image trigger,
is associated with highly absorbed optical/NIR transient emission
(Sudilovsky et al., GCN 15247), and lies at a relatively low redshift
(z = 0.347; Vreeswijk et al., GCN 15249; Sudilovsky et al., GCN 15250).

We encourage observations at all wavelengths to help determine the nature
of this interesting source.
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