GCN Circular 15066

K.Varela (MPE Garching), P.Afonso (American River College) and J.Greiner
(MPE Garching)report on behalf of the GROND team :

We observed the field GRB 130803A (Swift trigger 565263; Page et al.,
GCN 15059
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 ) simultaneously in g'r'i'z'JHKs with GROND (Greiner et al.2008,
PASP 120, 405) mounted at the 2.2m MPG/ESO telescope at La Silla
Observatory (Chile).

Observations started at 23:13 UT on August 3, about 13.2 hours after
the trigger at a mean seeing of 1.8 arcsec and a mean airmass of 1.3. We
detect an extended source inside the enhanced 1.4'' XRT error circle
(Swift webpage). This could be the GRB host, though at the moment no
statement about variability can be made.

For stacked integration times of 100 min. in JHK and ~ 125min in griz, we
present the following preliminary magnitudes and ULs at the 3 sigma level:

g' = 25.6 +/- 0.4 mag,
r' = 24.4 +/- 0.3 mag,
i' = 23.8 +/- 0.2 mag,
z' = 23.4 +/- 0.3 mag,
J > 23.2 mag,
H > 22.5 mag, and
K > 22.2 mag.

Given magnitudes are calibrated against GROND zeropoints as well as 2MASS
field stars and are not corrected for the expected Galactic foreground
extinction corresponding to a reddening of E(B-V) = 0.05 mag in the
direction of the burst (Schlegel et al. 1998).