[vsnet-grb-info 20926] GRB 180720B: D50 optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23024
SUBJECT: GRB 180720B: D50 optical observations
DATE:    18/07/23 20:21:57 GMT
FROM:    Jan Strobl at AI AS CR,Ondrejov  <jan at strobl.cz>

M. Jelinek, J. Strobl, R. Hudec, C. Polasek (ASU CAS Ondrejov)
report:

We observed the position of the bright GRB 180720B (Siegel et al., GCN 
22973 & GCN 22975) with the D50 telescope of the Astronomical Institute 
Ondrejov, near Prague, Czech Republic. We performed a series of ~300x 20s 
unfiltered exposures as soon as the position became accessible above local 
horizon, between 9.8 and 12h after the trigger.

The optical afterglow (Martone et al., GCN 22976; Sasada et al., GCN 
22977; Reva et al., GCN 22979; Itoh et al., GCN 22983) is clearly detected 
in single 20 s images.

We confirm the stationary behaviour during our observations as reported by 
Kann et al. (GCN 22985) - the afterglow might have faded as few as 0.04 
mag between 10 and 11h after the GRB trigger.