[vsnet-grb-info 15665] GRB 141026A: GROND observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16953
SUBJECT: GRB 141026A: GROND observations
DATE:    14/10/26 05:56:23 GMT
FROM:    Alexander Kann at TLS Tautenburg  <kann at tls-tautenburg.de>

K. Varela (MPE Garching), D. A. Kann (TLS Tautenburg), and J. Greiner (MPE
Garching) report on behalf of the GROND team:

We observed the field of GRB 141026A (Swift trigger 616502; Hagen et al.,
GCN #16950) 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 02:51 UT on October 26th, approximately 15 min
after the GRB trigger. They were performed at high airmass (2.5 but
rising) but decent seeing (1".2).

At the position of the P60 candidate (Perley, GCN #16951) we do not detect
any source. We find a source just to the north of the 5".8 Swift-XRT error
circle reported by Hagen et al. at

RA (J2000.0) = 02:56:20.16
DEC (J2000.0) = +26:55:41.4

with an error of 0".5. This source is also reported by RATIR (Littlejohns
et al., GCN #16952). We do not find any variability within errors over the
course of our observations. It is likely not associated with the GRB.

Based on images with an exposure time of 1500 s in the optical and 1200 s
in the NIR, centered at 0.05598 days after the trigger, we estimate
preliminary magnitudes and limits (all in AB system) for this source of:

g' = 23.2 +/- 0.1 mag
r' = 21.8 +/- 0.1 mag
i' = 21.5 +/- 0.1 mag
z' = 21.2 +/- 0.1 mag
J = 20.9 +/- 0.3 mag
H = 20.5 +/- 0.3 mag
K > 18.7 mag

Given magnitudes are calibrated against GROND zeropoints (g'r'i'z') and
2MASS field stars (JHK) and are not corrected for the expected Galactic
foreground extinction corresponding to a reddening of E_(B-V)=0.18 mag in
the direction of the burst (Schlegel et al. 1998).