[vsnet-grb-info 17938] GRB 160504A: NOT upper limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19385
SUBJECT: GRB 160504A: NOT upper limits
DATE:    16/05/04 22:22:05 GMT
FROM:    Thomas Kruehler at MPE Garching  <kruehler at mpe.mpg.de>

T. Kruehler (MPE Garching), A. de Ugarte Postigo (IAA-CSIC and
DARK/NBI), and T. Kuutma (NOT) report on behalf of a larger
collaboration:

We observed the field of GRB 160504A (Malesani et al., GCN #19382)
with the NOT equipped with ALFOSC. Imaging in the r, i and z-band
filter started at 20:54:10 UT on 2016-05-04, 1.4 hr after the GRB
trigger.

We detect no sources in the enhanced XRT error circle given at
http://www.swift.ac.uk/sper/685124/.

Calibrating our images against magnitudes from field stars of the
SDSS catalog, we measure preliminary upper limits of

r > 23.3 mag
i > 22.8 mag
z > 22.0 mag

These limits are not corrected for the expected foreground
extinction corresponding to a reddening of E(B-V) = 0.01 mag
(Schlafly & Finkbeiner 2011).