TITLE: GCN CIRCULAR NUMBER: 16724 SUBJECT: GRB140819A: Deep GROND Upper Limits DATE: 14/08/20 01:31:51 GMT FROM: Sebastian Schmidl at TLS Tautenburg S. Schmidl (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 140819A (Fermi trigger 430148973; optical candidate: Lipunov et al., GCN #16720) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m MPG telescope at ESO La Silla Observatory (Chile). Observations started on August 19, 2014, at 23:42 UT, 9.9 hrs after the GRB trigger. They were performed at an average seeing of 1.0" and at an average airmass of 1.1. We do not detect a source at the postion of the afterglow candidate reported by Lipunov et al. (GCN #16720). Based on a total exposure of 25 minutes in g'r'i'z'and 20 minutes in JHK, at a midtime of 0.42 days after the burst, we measure the following preliminary upper limits (AB magnitudes system): g' > 25.0, r' > 25.0, i' > 24.1, z' > 23.6, J > 20.9, H > 20.7, and K > 18.8. These derived upper limits are significantly deeper than those reported beforehand (Espartero et al., GCN #16772, Dichiara et al., GCN #16773). The decay slope between the 10th magnitude detection at a minute after the GRB and r' > 25 mag at 10 hours implies a decay slope > 2. Such a steep slope over a prolonged period of time is unlikely. Note that if the transient is not seen already in the second image taken by MASTER, an even steeper slope is implied (assuming a magnitude limit of 12.6 for the image). We therefore propose the optical transient is unassociated with the GRB, and may be due to, e.g., a glint off a tumbling object in near Earth orbit. Given magnitudes are calibrated against GROND zeropoints as well as 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.58 mag in the direction of the burst (Schlegel et al. 1998).