TITLE:   GCN CIRCULAR
NUMBER:  9923
SUBJECT: GRB 090915: GROND upper limits
DATE:    09/09/17 20:18:51 GMT
FROM:    Robert Filgas at MPI  <filgas@mpe.mpg.de>

P. Afonso (MPE Garching), A. Updike (Clemson University), J. Greiner and R.
Filgas (MPE Garching) report on behalf of the GROND team:

GROND (Greiner et al. 2008, PASP 120, 405), mounted at the 2.2m ESO/MPI
telescope at La Silla Observatory (Chile), observed the field of GRB 090915
(Cummings and Markwardt 2009, GCN #9912) simultaneously in the g'r'i'z'JHK
bands.

With 8 min total integration time in JHK and 7.7 min in g'r'i'z',
observations started on September 17, at 00:19 UTC (32.7 h = 117.8 ksec
after the burst) and were done at high air mass and under variable sky
conditions.

Inside the enhanced XRT error circle we do not detect the object reported
by Beardmore et al. (GCN #9914), Hoversten and Sakamoto (GCN #9918) and
Updike et al. (GCN #9920), down to the following limiting magnitudes (all
in the AB system):

g' > 23.7
r' > 23.2
i' > 22.7
z' > 21.3
J  > 21.1
H  > 20.2
K  > 19.2

The upper limits were obtained using SDSS and 2MASS catalogs
field stars as reference. No correction has been made for the expected
extinction corresponding to E(B-V) = 0.05 mag in the direction of the burst
(Schlegel et al. 1998).

The non-detection of the source suggests this was indeed the
afterglow of GRB 090915.