[vsnet-grb-info 4858] GRB 070628: NIR detection of afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6590
SUBJECT: GRB 070628: NIR detection of afterglow
DATE:    07/06/29 19:54:12 GMT
FROM:    Jochen Greiner at MPI  <jcg at mpe.mpg.de>

N. Primak, G. Szokoly, J. Greiner, C. Clemens, T. Kruehler, A. Kuepcue-Yoldas, 
A. Yoldas (all MPE Garching), S. Klose, A. Rossi (Tautenburg Observatory), 
and F. Carrier (Instituut voor Sterrenkunde Leuven, Belgium) report:

We observed the field of GRB 070628 (Swift trigger 283320; Holland et al., 
GCN 6584) with GROND at the 2.2m Max-Planck Institute telescope at the 
ESO La Silla observatory in Chile. The observations started at 22:21:57, 
about 7.7 hrs after the GRB and just after sunset, and lasted 10 min. 
We observed simultaneously in the g,r,i,z,J,H,K bands. The UVOT afterglow
(Cronwall & Holland, GCN 6585) is clearly detected at H=16.2+-0.3 and 
K=16.3+-0.2 mag. The NIR magnitudes are calibrated against 2MASS. 
Nothing is visible in the J band (limiting magnitude 16.0), and all 
optical frames are saturated due to twilight. 

We note that the afterglow was atypically bright for the given time after
the burst, suggesting a slow fading. We encourage near-IR spectroscopy to
determine the redshift.