[vsnet-grb-info 6850] GRB 081028: GROND Confirmation of the Optical/NIR Afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8442
SUBJECT: GRB 081028: GROND Confirmation of the Optical/NIR Afterglow
DATE:    08/10/29 09:00:11 GMT
FROM:    Christian Clemens at MPE  <cclemens at mpe.mpg.de>

C. Clemens, T. Kruehler and J. Greiner (all MPE Garching) report on behalf of 
the GROND team:

We observed the field of GRB 081028 for a second time at 07:45 UT on October 
29th, 2008, 31.3 hr after the GRB trigger with 460 s of total exposures in 
g'r'i'z' and 480 s in JHK. Observations were performed at an average seeing 
of 1.3" and at an average airmass of 1.5.

We still detect the bright afterglow within the refined 1.5'' Swift-XRT error 
circle (Evans et al., GCN #8427) with the following preliminary magnitudes 
(all in AB system) of

g' ~ 21.26 mag,
r' ~ 20.49 mag,
i' ~ 20.24 mag,
z' ~ 19.99 mag and
J ~ 19.6 mag

with statistical errors of +/- 0.05 in g'r'i'z' and +/- 0.1 in J. Given 
magnitudes are calibrated against SDSS as well as 2MASS field stars.

These measurements demonstrate a strong fading of the source compared to our 
first epoch observations (Clemens et al., GCN #8424). We therefore confirm 
this to be the afterglow of GRB 081028.

No correction for the Galactic foreground extinction corresponding to a 
reddening of E_(B-V)= 0.03 mag in the direction of the burst (Schlegel et al. 
1998) has been applied.