TITLE:   GCN CIRCULAR
NUMBER:  14173
SUBJECT: GRB 130131B: GROND Upper limits
DATE:    13/02/01 14:07:31 GMT
FROM:    Karla Varela at MPE  <kvarela@mpe.mpg.de>

F.Knust, K.Varela, J.Greiner (all MPE Garching) report on behalf of the
GROND team:

We observed the field of GRB 130131B (Swift trigger 547420; Siegel et al.,
GCN 14159) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla
Observatory (Chile).

Observations started at 04:00 UT on February 1st, 9 hrs after the GRB
trigger, only 27 deg away from the moon. They were performed at an average
seeing of 2.9” and at an average airmass of 1.6.

We do not detect a source within the Swift-XRT error circle reported by
Goad et al. (GCN 14165) down to 3-sigma AB limiting magnitudes

g' > 23.4,

r' > 23.7,

i' > 23.4,

z' > 23.3,

J > 21.2,

H > 20.5 and

K > 19.7

The given limits are derived based on calibrating the images against GROND
zeropoints in g'r'i'z' and 2MASS field stars in JHK and are not corrected
for the Galactic foreground extinction corresponding to a reddening of
E_(B-V)= 0.03mag in the direction of the burst (Schlegel et al. 1998).