GCN Circular 15489
Subject
GRB 130925A: HST imaging
Date
2013-11-16T09:22:23Z (10 years ago)
From
Nial Tanvir at U.Leicester <nrt3@star.le.ac.uk>
N. R. Tanvir (U. Leicester), A. J. Levan (U. Warwick), R. Hounsell,
A. S. Fruchter (STScI), S. B. Cenko (NASA/GSFC), D. A. Perley (Caltech),
P. T. O'Brien (U. Leicester) report:
We imaged the location of GRB 130925A (Evans et al. GCN 15251;
Sudilovsky et al. GCN 15247) with HST at two epochs, at 20 days and
47 days post-burst respectively, in the F814W (I-band), F110W (J-band)
and F160W (H-band) filters.
The host galaxy is well resolved and appears to be an almost edge-on spiral.
The galaxy shows signs of disturbance: specifically the disk shows asymmetry
and the bulge appears to be extended perpendicular to the disk, suggestive
of a polar-ring morphology.
Image subtraction reveals evidence of faint transient light in the first epoch
in all three filters. The location is in good agreement with that from prior
ground-based imaging of the GRB. The transient position is close to the disk
plane, which likely accounts for the high extinction and X-ray column for this
event (Evans et al. GCN 15254). It is, however, slightly offset from the
nucleus of the galaxy by about 0.12 arcsec (~600pc in projection). This
would initially seem to be in conflict with a possible tidal disruption origin
for this event, although if the galaxy morphology is indicative of a recent
major merger, then it is plausible that the system currently contains more
than one super-massive black hole.
Further analysis is ongoing.
We thank the staff at STScI for approving and expediting
these ToO observations.