TITLE:   GCN CIRCULAR
NUMBER:  32096
SUBJECT: GRB 220521A: REM optical/NIR upper limits
DATE:    22/05/23 20:14:11 GMT
FROM:    Paolo D'Avanzo at INAF-OAB  <pda.davanzo@gmail.com>

M. Ferro, R. Brivio, A. Melandri, P. D'Avanzo, S. Covino, D. Fugazza, (INAF-OAB) on behalf of the REM team, report:

We observed the field of GRB 220521A (Fermi/GBM team GCN Circ. 32075; Dichiara et al., GCN Circ. 32076) with 
the REM 60cm robotic telescope  located at the ESO premise of La Silla (Chile). The observations were carried in the 
g, r, i, z, J, H and K bands, starting on 2022 May 22 at 02:24:40 UT (i.e. about 3.1 hours after the burst) and lasting for 
about one hour. 

The optical afterglow (Malesani et al., GCN Circ. 32078) is not detected. From preliminary photometry we derive the 
following magnitude upper limits (3sigma c.l.): 

g > 19.5
r > 19.1
i > 18.8
z > 17.4
(AB; calibrated against the Pan-STARRS catalogue) at a mid time of t-t0 ~ 3.5 hours;

J > 16.6
H > 16.2
K > 13.5
(Vega; calibrated against the 2MASS catalogue) at a mid time of t-t0 ~ 3.9 hours.