TITLE:   GCN CIRCULAR
NUMBER:  24711
SUBJECT: GRB 190531B: VLT optical upper limit
DATE:    19/06/01 20:38:26 GMT
FROM:    Jure Japelj at API,U of Amsterdam  <japelj.jure@gmail.com>

J. Japelj (U. Amsterdam), A. Rossi (INAF-OAS), D. B. Malesani
(DTU Space), K. E. Heintz (Univ. Iceland), G. Pugliese, L. Kaper
(U. Amsterdam) report on behalf of the Stargate collaboration:

We observed the field of GRB 190531B (Fermi GBM team, GCN 24695;
Kunzweiler et al., GCN 24696; Axelsson et al., GCN 24701) with the ESO VLT
UT2 (Kueyen), using the X-shooter acquisition camera. A 3x30 s exposure
with the SDSS r filter was taken at approximate time 2019 June 1.39 UT
(0.55 days after GRB).

We do not detect any new object within the error region of the detected
X-ray afterglow (D'Avanzo et al., GCN 24706), down to a 3-sigma
limiting magnitude r > 23 AB (calibrated against nearby star at position
RA=01:37:12.696, Dec=-41:57:36.702). The closest source to the XRT error
circle is at RA=01:37:11.37, Dec=-41:57:30.73, which is 3.1 arcsec away
from the XRT location, and is thus unlikely to be related to the GRB.

We acknowledge excellent support from the observing team in Paranal,
in particular Alex Correa, Florian Rodler and Pascale Hibon.