[vsnet-grb-info 20616] GRB 180512A: GROND upper limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22714
SUBJECT: GRB 180512A: GROND upper limits
DATE:    18/05/13 02:42:32 GMT
FROM:    Jan Bolmer at MPE/Garching  <jan at bolmer.de>

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.