TITLE:   GCN CIRCULAR
NUMBER:  28750
SUBJECT: GRB 201020B: Konkoly Obs. optical detection
DATE:    20/10/22 18:48:16 GMT
FROM:    Jozsef Vinko at Konkoly Observatory  <vinko@konkoly.hu>

J. Vinko (Konkoly/ELTE/U Szeged), A. Pal, L. Kriskovics, R. Szakats, A. Ordasi and K. Vida (Konkoly)
report on behalf of the "Transient Astrophysical Objects" project:

We observed the field of GRB 201020B (Fermi team, GCN 28702; Lipunov et al. GCN 28704;
Malacaria and Meegan, GCN 28710; Ursi et al. 28714; Arimoto et al., GCN 28716;
Lipunov et al., GCN 28718; Xu et al., GCN 28719; Ridnaia et al., GCN 28723;
Belkin et al., GCN 28725; Sbarufatti et al., GCN 28740; Breeveld et al., GCN 28743)
with the 0.8m RC80 robotic telescope at Piszkesteto Mountain Station of Konkoly Observatory
through SDSS r' and i' filters (exposure time 3 x 300 sec per filter)
on 2020 Oct 21.807 UT (MJD 59143.807; 25.8 hours = 92880 s after the trigger).
The frames were tied to PS1-photometry of local stellar sources.
An optical afterglow of the GRB has been detected with the following AB-magnitudes:

r' = 20.869 +/- 2.311 AB mag
i' = 19.368 +/- 0.696 AB mag

which are consistent with previous detections of the fading afterglow.