TITLE:   GCN CIRCULAR
NUMBER:  24709
SUBJECT: GRB 190530A: Konkoly optical observations of the afterglow
DATE:    19/06/01 18:26:08 GMT
FROM:    Jozsef Vinko at Konkoly Observatory  <vinko@konkoly.hu>

J. Vinko, R. Szakats, A. Pal, L. Kriskovics, A. Ordasi, K. Sarneczky
(MTA CSFK Konkoly Observatory) report:

The optical afterglow (Lipunov et al., GCN 24680; Kann et al., GCN 24684; Heintz et al., GCN 24686;
Izzo et al., GCN 24687; Xin et al., GCN 24688; Watson et al., GCN 24690; Lipunov et al., GCN 24693;
Xin et al., GCN 24697; Belkin et al.,  GCN 24698; Kann et al., GCN 24700; Siegel, GCN 24703;
Moskvitin and Uklein, GCN 24708) of the bright GRB 190530A (Fermi GBM team, GCN 24676, Biltzinger et al.,
GCN 24677;  Longo et al., GCN 24679; Lucarelli et al.,GCN 24678, Verecchia et al., GCN 24683)
is marginally detected on the stacked Sloan-r band CCD frames (total exposure time 45 min)
taken with the 0.8m RC80 telescope at Konkoly Observatory, Piszkesteto (Hungary)
on 2019-05-31.35 UT, 1.42 day after the burst.
                          
Aperture photometry on the stacked frame, tied to PS1 r-band data of 19 local comparison
stars resulted in the following AB magnitude for the transient:
                          
r_PS1 (AB) = 19.86 +/- 0.37 mag

This is consistent with R-band brightness (~19.39 +/- 0.05 AB-mag at 1.353 days after burst) reported by
Moskvitin and Uklein (GCN 24708), but significantly brighter than the one measured by Kann
et al. (GCN 24700, Rc ~ 20.60 +/- 0.15 AB-mag at 1.44509 day after burst).

Further monitoring of this interesting transient is encouraged.