TITLE: GCN CIRCULAR NUMBER: 15253 SUBJECT: GRB 130925A: Initial Similarities to Swift J1644+57 DATE: 13/09/25 14:59:41 GMT FROM: 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: http://www.swift.ac.uk/xrt_curves/00571830/ 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.