F. Knust (MPE Garching), A. Nicuesa Guelbenzu (TLS Tautenburg)
and J. Greiner (MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 130206A (Swift trigger 547918; De Pasquale
et al.,GCN 14181) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.
2008, PASP 120, 405) mounted at the 2.2m MPG/ESO telescope at La Silla
The first observations started at 01:10 UT on 07 Feb 2013, 6.5 hrs after
the GRB trigger, and a second epoch was taken at 7:47 UT on 8 Feb 2013.
These observations were performed at an average seeing of 1.4/1.0 arcsec
and at an average airmass of 1.3/1.4.
We detect three sources within the 5.6 arcsec Swift-XRT error circle
(Beardmore et al., GCN 14188), at positions:
RA (2000.0) = 09h 21m 30.45s
Decl. (2000.0) = -58d 11' 34.7"
RA (2000.0) = 09h 21m 30.10s
Decl. (2000.0) = -58d 11' 36.5"
RA (2000.0) = 09h 21m 30.14s
Decl. (2000.0) = -58d 11' 41.2"
with an uncertainty of 0.5" in each coordinate.
For the aforementioned three sources, the preliminary photometry does
not show any variability. Image subtraction between the two epochs
has revealed no residuals either.
Based on exposures of 42 min in g'r'i'z' and 54 min in JHK,
we do not detect the afterglow within the 5.6" XRT error circle
to the following 3-sigma upper limits (AB system):
g' > 24.7,
r' > 24.6,
i' > 23.8,
z' > 23.8,
J > 21.6,
H > 21.2 and
K > 20.6
The given limits are derived based on calibrating the images against GROND
zeropoints and 2MASS field stars and are not corrected for the Galactic
foreground extinction corresponding to a reddening of E_(B-V)= 0.5 in the
direction of the burst (Schlegel et al. 1998).