[vsnet-grb-info 7495] GRB 090328: GROND Detection of the Optical/NIR Afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9054
SUBJECT: GRB 090328: GROND Detection of the Optical/NIR Afterglow
DATE:    09/03/30 03:36:16 GMT
FROM:    Adria C. Updike at Clemson U  <aupdike at clemson.edu>

Adria Updike (Clemson University), Sylvio Klose (Tautenburg Obs.),
Christian Clemens and Jochen Greiner (MPE Garching) report on behalf of
the GROND team:

We observed the field of GRB 090328 (Fermi trigger 259925808; McEnergy et
al., GCN 9044) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.
2008, PASP 120, 405) mounted at the 2.2 m ESO/MPI telescope at La Silla
Observatory (Chile).

Observations started at 23:24 UT on date, about 1.6 days after the GRB
trigger, and are continuing. They were performed at an average seeing of
1.8" and at an average airmass of 1.06.

We detect the afterglow reported by Kennea et al. (GCN 9045) in all bands.

Based on the first 8 min of total exposures in g'r'i'z' JHK, we estimate
preliminary magnitudes (all in AB system) of

g' = 20.97 +/- 0.05 mag,

r' = 20.23 +/- 0.03 mag,

i' = 19.89 +/- 0.04 mag,

z' = 19.54 +/- 0.03 mag,

J = 19.54 +/- 0.06 mag,

H = 19.02 +/- 0.06 mag and

K = 18.52 +/- 0.08 mag

Given magnitudes are calibrated against USNO as well as 2MASS field stars
and are not corrected for the expected Galactic foreground extinction
corresponding to a reddening of E_(B-V) = 0.06 mag in the direction of the
burst (Schlegel et al. 1998).