GCN Circular 17419

T. Schweyer (MPE Garching), S. Schmidl (TLS Tautenburg), and J. Greiner
(MPE Garching) report on behalf of the GROND team:

We observed the field of GRB 150206A (Swift trigger 630019; Hagen et al.,
GCN 17413
Not found
 
 
) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla
Observatory (Chile).

Observations started at 00:32 UT on February 07, 2015, 10 hrs after the
GRB trigger. They were performed at an average seeing of 1.4" and at an
average airmass of 1.7.

We detect the optical aftergow canditate reported by Hagen et al. (GCN
17413
Not found
 
 
).

Based on total exposures of 8.8 minutes in g'r'i'z' and 8.0 minutes in
JHK, at a midtime of 10.3 hrs after the burst, we measure the following
preliminary magnitudes and upper limits (all AB magnitude system):

g' = 22.6 +/- 0.2 mag,
r' = 21.9 +/- 0.1 mag,
i' = 21.2 +/- 0.1 mag,
z' = 20.8 +/- 0.1 mag,
J = 20.0 +/- 0.2 mag,
H > 20.2 mag, and
K > 19.4 mag.

The magnitudes are calibrated against GROND zeropoints and 2MASS field
stars and are not corrected for the Galactic foreground extinction
corresponding to a reddening of E_(B-V)= 0.02 in the direction of the
burst (Schlegel et al. 1998).