GCN Circular 6259
Subject
GRB 070406: Gemini South Imaging and XRT analysis
Event
Date
2007-04-08T05:05:48Z (19 years ago)
From
Josh Bloom at UC Berkeley <jbloom@astron.berkeley.edu>
J. S. Bloom (UC Berkeley), H-W. Chen (Chicago), J. X. Prochaska (UC
Santa Cruz), N. R. Bulter (UC Berkeley) report:
We observed the field of GRB 070406 (Cummings et al.; GCN 6247) with
the GMOS instrument on Gemini South in r and i-band filters. An i-
band finder is provided (*) with mean epoch 7.26 April 2007 UT (~29.4
hours after the GRB). The images cover the region of the XRT source
(Troja et al.; GCN 6255). Our re-analysis of the XRT data, based on
the first 20 ks and allowing for the possiblity of an astrometric XRT
frame offset, yields a moderately larger XRT error circle (labeled
"Butler") of:
RA(J2000) = 13:15:51.16 DEC = +16:30:47.7 (6.4" at 90%
confidence)
We cannot confirm any variability of the X-ray source. The SDSS
galaxy noted by Kann (GCN 6256) and the faint source noted by
Malesani et al. (GCN 6257) are well detected. We note that the
Malesani source appears to be resolved and it thus unlikely to be the
afterglow (it also appears marginally detected in the SDSS i-band
image from Cool et al. GCN 6248). We note 5 additional sources in the
XRT error circle (J2000):
RA DEC
s1 13:15:51.41 +16:30:42.6
s2 13:15:51.19 +16:30:41.9
s3 13:15:50.94 +16:30:42.6
s4 13:15:50.75 +16:30:48.0
s5 13:15:51.48 +16:30:52.7
We make no claims about variability at this time.
We find no source at the location of the Xin et al. transient (GCN
6253). However, we do detect a faint source ~2.3 arcseconds to the
South West of that position at:
OT? 13:15:40.91 16:34:13.1
This source is several magnitudes fainter than the galaxy to the
northwest noted by Xin et al., whereas Xin et al. indicate that their
source was 4 magnitudes brighter at 35.4 hour after the GRB."
This message can be cited.
(*) http://lyra.berkeley.edu/~jbloom/grb070406_ep1.pdf
GRAASP thanks to Henry Lee and the observing team at Gemini South for
performing these ToO observations.