TITLE:   GCN CIRCULAR
NUMBER:  24492
SUBJECT: GRB 190511A: NOT optical afterglow
DATE:    19/05/11 22:13:23 GMT
FROM:    Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst  <malesani@dark-cosmology.dk>

Daniele B. Malesani (DAWN/NBI and DARK/NBI), Dong Xu (NAOC/CAS), Joonas 
Viuho (NOT and DAWN/NBI) report on behalf of a larger collaboration:

We observed the field of the Swift and Fermi GRB 190511A (Bernardini et 
al., GCN 24472; von Kienlin, GCN 24482; Axelsson et al., GCN 24483) 
using the Nordic Optical Telescope (NOT) equipped with the AlFOSC 
camera. Observations started in twilight and were carried out at high 
airmass due to the poor target visibility.

Just outside the enhanced XRT error position (Goad et al., GCN 24481), 
we clearly detect a source not visible in the archival Pan-STARRS images 
of the same area, which we suggest to be the optical afterglow of GRB 
190511A. Its coordinates are (J2000):

RA = 08:25:46.46
Dec = -20:15:33.4

Using nearby stars from the Pan-STARRS survey as calibrators, we measure 
for the afterglow a magnitude r = 20.89 +- 0.09 AB, at a mean epoch May 
11.8648 UT (13.51 hr after the trigger).