GCN Circular 13579
Subject
GRB 120804A: GROND upper limits
Event
Date
2012-08-04T09:07:02Z (14 years ago)
From
Vladimir Sudilovsky at MPE <vsudilov@mpe.mpg.de>
V. Sudilovsky, J. Elliott, and J. Greiner (all MPE Garching) report
on behalf of the GROND team:
We observed the field of GRB 120804A (Swift trigger 529686; Lien et al.,
GCN 13573) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla
Observatory (Chile).
Observations started at 02:22 UT on 2012-08-04, 1.5 hrs after the GRB
trigger. We do not detect any sources within the XRT position reported by
Osborne et al (GCN 13577). We do note that observations were severely
limited by unfavorable weather conditions, including moon-illuminated
visible cirrus towards the field.
Based on six co-added exposures of 370s (g'r'i'z') and 240s (JHK) taken
at a mean airmass of 1.3 and a mean seeing of 3.0", we derive the following
upper limits (all AB system):
g' > 21.9
r' > 22.1
i' > 22.0
z' > 21.9
J' > 20.6
H' > 20.0
K' > 19.5
The magnitudes are derived based on GROND zeropoints (g'r'i'z') and 2MASS
stars (JHK). The above upper limits are not corrected for the Galactic
extinction
of E(B-V) = 0.23 mag along the line of sight (Schlegel et al. 1998).