SUBJECT: GRB100401A, GROND Upper Limits
A. Updike (Clemson University), A. Rau, P. Afonso and J. Greiner (all
MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 100401A (Cummings et al., GCN #10567,
Goldstein and Gruber, #GCN 10568) simultaneously in g'r'i'z'JHK with
GROND (Greiner et al. 2008,PASP 120, 405), mounted at the 2.2m ESO/MPI
telescope at La Silla Observatory (Chile).
Observations started on 2010, April 3, at 09:21 UT, 2.09 days after the
burst, and consisted of 20 min in JHK and 24.6 min in g'r'i'z'. A second
epoch was obtained on 2010, April 4, at 09:09 UT, 2.99 days after the burst.
Image subtraction of the two epochs does not reveal a variable source,
down to the following 1st epoch limiting magnitudes (all in AB system):
g' > 23.7
r' > 23.9
i' > 23.4
z' > 23.4
J > 21.8
H > 21.4
K > 20.3
These magnitudes were obtained using 2MASS field stars and GROND
zero-points as reference, and are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.29 mag in the direction of
the burst (Schlegel et al. 1998).