TITLE:   GCN CIRCULAR
NUMBER:  24751
SUBJECT: GRB 190530A: optical follow-up observations at Konkoly
DATE:    19/06/05 13:27:40 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:

We took follow-up observations on 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; Vinko et al., GCN 24709; 
Belkin et al., GCN 24712; Kumar et al., GCN 24729; Nandi et al., GCN 24745) 
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). 

The source was clearly detected on the stacked Sloan-r band CCD frames (total exposure time 60 min)
taken with the 0.8m RC80 telescope at Konkoly Observatory, Piszkesteto (Hungary)
on 2019-06-01.85 UT, but only marginally detected on the frames taken 
on 2019-06-02.86 UT (2.42 and 3.43 days after burst, respectively).

We measured the brightness of the transient via aperture photometry on the stacked 
r-band frames using PS1 r-band magnitudes of 19 local comparison stars. The results, 
corrected for the contamination of the nearby faint source (r_PS1(AB) = 20.947 +/- 0.0565 mag),
are as follows:

# Date      UT(mid)    JD-2400000     r(AB)  unc.   Ref
#----------------------------------------------------------------
2019-05-31 20:23:35   58635.349711    20.36  0.37   GCN 24709
2019-06-01 20:23:56   58636.349953    20.15  0.11   this circular
2019-06-02 20:37:30   58637.359375    22.10  0.41   this circular
#----------------------------------------------------------------

Note that in Vinko et al. (GCN 24709) the UT date of the observation was 
reported incorrectly. The correct date was 2019-05-31.85 UT. Also, our 
previous photometry given in GCN 24709 was not corrected for the nearby 
contaminating source. The table above contains the updated, corrected 
magnitudes.

Our last photometric measurement (taken on 2019-06-02) is consistent with the
R-band magnitude reported by Kumar et al. (GCN 24729, R ~ 21.3 +/- 0.3 mag).