GCN Circular 9352
Subject
GRB 090510: GROND observations
Event
Date
2009-05-12T15:19:57Z (16 years ago)
From
Thomas Kruehler at MPE/MPI <kruehler@mpe.mpg.de>
F. Olivares (MPE Garching), S. Klose (Tautenburg), T. Kruehler, J. Greiner
(both MPE Garching) report on behalf of the GROND team:
GROND, mounted at the 2.2m on La Silla, observed the field of GRB 090510,
detected by Swift (Hoversten et al., GCN 9331), Fermi GBM (Guiriec et al.,
GCN 9336) and LAT (Ohno & Pelassa, GCN #9334), AGILE (Longo et al., GCN
9343) and Konus-Wind (Golenetskii et al., GCN 9344), in g'r'i'z'JHK
starting at 6:34 UT on 10 May 2009.
We detect the afterglow reported by Marshall & Hoversten (GCN #9332) and
Olofsson et al. (GCN #9338) in the optical bands. At a midtime of 9.0 h
after the burst, we measure the following AB magnitudes of the afterglow
and upper limits in stacked images
g' = 23.5 +/- 0.3
r' = 23.0 +/- 0.1
i' = 22.8 +/- 0.1
z' = 22.6 +/- 0.1
J > 21.8
H > 21.4
K > 20.7
calibrated against the GROND zeropoints and 2MASS field stars. We caution
that the photometry might be contaminated by the nearby source mentioned by
Olofsson et al. (GCN #9338).
Together with the magnitude reported by NOT (Olofsson et al. GCN #9338),
this implies a rapid early fading with an index of ~2 during this epoch,
which is compatible to the X-ray afterglow at a similar time interval
(Grupe & Hoversten, GCN #9341). A late flattening of the optical light
curve is then indicated by the UVOT detection (Kuin et al. #GCN 9351).