GCN Circular 10835
A. Nicuesa (TLS Tautenburg), T. Kruehler and J. Greiner (MPE Garching) report on behalf of the GROND team: We observed the field of GRB 100606A (Oates et al., GCN 10824) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPI/ESO telescope at La Silla Observatory (Chile). Observations started at 04:27 UT on June 07, 9.2 hours after the GRB trigger. Within the enhanced XRT error circle (Evans et al. GCN 10827) we confirm the presence of the blue and extended source reported by Levan et al. (GCN 10831) in g' and r' at RA (J2000.0) = 23:22:30.27 Dec (J2000.0) = -66:14:27.1 with typical uncertainties of 0.5" in each coordinate. Similar to Levan et al. (GCN 10831) we also do not find evidence of an optical/NIR afterglow. Stacked images of 270 min total integration time in g'r'i'z' and 80 min in JHK yield the following preliminary upper limits in the AB system, which have been obtained using the GROND zeropoints and 2MASS field stars as reference: g' > 25.7 (24.7 +- 0.2) r' > 25.5 (25.0 +- 0.3) i' > 24.6 z' > 24.1 J > 22.2 H > 21.5 K > 21.0 Magnitudes in brackets denote the brightness of the putative host galaxy. Using the r'-band upper limit and the X-ray brightness at a similar time, beta_oX is constrained to be smaller than 0.6, implying that the burst would not be necessarily 'dark' according to the Jakobsson et al. (2004, ApJ, 617, 21) classification. Thus, our limit neither implies large redshift nor large extinction.