[vsnet-grb-info 11513] GRB 120202A: WHT, Gemini & UKIRT candidate afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  12912
SUBJECT: GRB 120202A: WHT, Gemini & UKIRT candidate afterglow
DATE:    12/02/03 22:14:28 GMT
FROM:    Nial Tanvir at U.Leicester  <nrt3 at star.le.ac.uk>

N. R. Tanvir (U. Leicester), A. J. Levan (U. Warwick),
L. Domínguez Palmero (ING), S. Leggett (Gemini) & T. Wold (JACH)
report on behalf of a larger collaboration:

We imaged the field of GRB120202A (Mereghetti et al. GCN12909) using the
WHT/ACAM and Gemini-N/GMOS.  At the location of the X-ray source identified
by Holland et al. (GCN12911) we find a faint source at position:

13:34:00.80Â  +22:46:24.3

with the following provisional magnitudes (both photometry and astrometry are
calibrated against SDSS DS8):

WHT
r= 25.00 +/- 0.15Â  (approx 7:40 hours post-burst)

Gemini-N
r=24.84 +/- 0.09 (approx 16:10 hours post-burst)

Thus there is no clear evidence for variability. 
There is however another point source close to the reported Swift XRT
source at position:

13:34:01.27 +22:46:29.0

slightly outside the reported 90% error circle, for which
we find magnitudes:

WHT:Â Â Â 
r=24.68 +/- 0.09,   z=22.93 +/- 0.18

Gemini:Â Â 
r=24.26 +/- 0.06,   z=22.64 +/- 0.08

Thus, there is evidence of brightening for this source by about
0.3-0.4 mag between the two epochs, making it likely associated with
the GRB, albeit with unusual afterglow behaviour.  For this source we also
have a K-band magnitude from UKIRT/WFCAM:

K=18.35 +/- 0.18Â  (calibrated against 2MASS, taken at 15:00 hours post-burst)

indicating a very red colour from the provisional photometry.