GCN Circular 1520
Subject
Second epoch K band imaging of GRB 020819
Date
2002-08-23T09:03:18Z (23 years ago)
From
Jochen Greiner at MPI <jcg@mpe.mpg.de>
S. Klose (Thueringer Landessternwarte Tautenburg),
A. Henden (USRA/USNO),
J. Greiner (MPE Garching),
D. H. Hartmann (Clemson University),
N. Cardiel, J. Gallego (Universidad Complutense de Madrid), and
U. Thiele (Calar Alto Observatory)
report:
A deep second epoch K' band observation of the 130 arcsec radius error
circle of the HETE burst GRB 020819 (HETE trigger #2275, Seq_4;
Vanderspek et al. 2002, GCN #1508) has been performed on August 20/21,
23:11--00:59 UT (about 33 hrs after the GRB), using the Calar Alto
3.5-m telescope equipped with the Omega Prime near-infrared camera.
The integration time was 77 min. The limiting magnitude is about
K'=20.5 (+/-0.5), the seeing was 1.2 arcsec.
Lacking a K band photometric calibration, we used the (B-R) colors of all
USNO stars (Monet et al. 1996; http://asteroid.lowell.edu/cgi-bin/koehn/webnet)
in the field for a rough calibration. Assuming their colors are
representative for their spectral type and assuming zero interstellar
extinction, the magnitude of the candidate object reported in GCN #1510
(Henden et al. 2002) is found to have K'=17.6 (conservative error of 0.2 mag).
Photometry of all objects within the HETE/SXC error circle using PSF fitting
(Sextractor) did not reveal any source brighter than K'=19 which faded by
more than 0.1 mag between the first epoch (Henden et al. 2002, GCN #1510)
and this second epoch observation. This and the findings of Price et al.
2002 (GCN #1511) and Salamanca et al. 2002 (GCN #1512) imply that the
candidate object proposed earlier (Henden et al. 2002, GCN #1510) is very
unlikely the GRB afterglow.