GCN Circular 9319
Subject
GRB 090427: GROND observations
Date
2009-05-04T00:07:14Z (16 years ago)
From
Felipe Olivares Estay at MPE <felipe@mpe.mpg.de>
F. Olivares, T. Kruehler, J. Greiner (all MPE Garching) report on behalf of
the GROND team:
We observed the central area of the error box of GRB 090427 localized by the
IPN (Pal'shin et al., GCN #9277) simultaneously in g'r'i'z'JHK with GROND
mounted at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile).
Three adjacent pointings centered at
RA = 15,43,31.0 Decl. = -13,40,00
RA = 15,43,43.4 Decl. = -13,30,00 (center of IPN box)
RA = 15,43,55.0 Decl. = -13,20,00
have been observed with our 10x10 arcmin (in JHK) and 5.4x5.4 arcmin
(g'r'i'z') field-of-view, thus covering about 27% and 8% of the full error
box respectively (see sketch at http://www.mpe.mpg.de/~jcg/grb090427.html).
Observations started on 29 Apr. 2009 at 06:20 UT, 30.9 h after the burst,
and consisted, for each of the three fields, of a set of images with a
total integration time of 8 min in JHK and 7.7 min in g'r'i'z'. A second
epoch of all three fields was obtained on 30 Apr. 2009 starting at 05:18 UT.
Image subtraction of the two epochs does not reveal a variable source
in any of the three fields, down to limiting magnitudes (all in AB system)
of
g' > 23.9
r' > 23.8
i' > 23.5
z' > 23.2
J > 22.2
H > 21.7
K > 20.6
These magnitudes have been obtained using 2MASS field stars and the GROND
zeropoints as reference.