TITLE: GCN CIRCULAR NUMBER: 16953 SUBJECT: GRB 141026A: GROND observations DATE: 14/10/26 05:56:23 GMT FROM: Alexander Kann at TLS Tautenburg 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).