TITLE:   GCN CIRCULAR
NUMBER:  10545
SUBJECT: GRB 100324A: GROND observations
DATE:    10/03/26 13:59:40 GMT
FROM:    Felipe Olivares Estay at MPE  <felipe@mpe.mpg.de>

A. Updike (Clemson University), M. Nardini, A. Rau, F. Olivares, and
J.Greiner (all MPE Garching) report on behalf of the GROND team:

We observed the field of GRB 100324A (ground analysis of Swift/BAT
data, Cummings et al., GCN #10544) simultaneously in g'r'i'z'JHK with
GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m MPI/ESO
telescope at La Silla Observatory (Chile). Observations started on 24
March 2010 at 23:41 UT, 23.3 hours after the GRB. The field was
observed during a second epoch, starting at 00:10 UT on 26 March 2010,
47.9 hours after the burst.

Our i'-band and H-band observations cover 95% and 100% of the 2.5' BAT
error circle, respectively. Image subtraction between the two
observing epochs does not reveal any variable source. The first image,
consisting of 24.8 min exposure in g'r'i'z' and 20 min in JHK, yields
the following 3-sigma upper limits (both AB magnitudes):

i' > 23.6 mag
H > 21.6 mag

which were obtained using the GROND zero points and 2MASS field stars
as reference. The given magnitudes are not corrected for the
significant Galactic extinction corresponding to a reddening of E(B-V)
= 0.71 mag (Schlegel et al. 1998).