GCN Circular 22714
J. Bolmer MPE Garching) reports on behalf of the GROND Team: I observed the field of GRB180512A (Swift trigger 832119; Deich et al., GCN #22710) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m MPG telescope at the ESO La Silla Observatory (Chile). Observations started at 00:03 UT on 2018-05-13, 2.7 hrs after the GRB trigger. They were performed at an average seeing of 1.3'' and at an average airmass of 1.9. No source is detected within or close to the Swift-XRT error circle. Based on 40 min of exposure in g'r'i'z' and 41 min in JHK_s, at a mid-time of 00:44 UT, we derive the following preliminary upper limits (in AB system): g' > 25.4 mag, r' > 24.9 mag, i' > 24.0 mag, z' > 23.4 mag, J > 21.9 mag, H > 21.2 mag, and K_s > 20.2 mag. Given upper limits are calibrated against SDSS field stars in g'r'i'z' as well as 2MASS field stars in JHK_s. No correction for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.058 mag in the direction of the burst (Schlafly & Finkbeiner 2011) has been applied.