[vsnet-grb-info 4362] GRB 070224: WHT K-band imaging

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6147
SUBJECT: GRB 070224: WHT K-band imaging
DATE:    07/02/25 11:08:53 GMT
FROM:    Nial Tanvir at IofA U.Cambridge  <nrt at ast.cam.ac.uk>

E. Rol, N.R. Tanvir, R. Starling (U. Leicester) and P. Groot
(U. Nijmegen) report on behalf of a larger collaboration:

We observed the field of GRB 070224 with the WHT/LIRIS instrument
in poor seeing, beginning at Feb 24 23:06 UT.  Our 6 minute K-band
image reached a 3-sigma limit of K~19.2 (based on calibration via
four 2MASS stars in the field).

A later observation in better seeing, beginning at Feb 25 04:44 UT,
reached a limiting magnitude of K~19.7.

In both images within the XRT error circle (GCN 6143) we see a source
at the position of the candidate reported by Thoene et al. (GCN 6142),
with a magnitude that is consistent with K~19.2 in both cases,
although some fading can't be ruled out.

In the second image we also see (close to the limit) another source
with (2000) coordinates approximately:

 11 56 06.26   -13 19 50.0