TITLE:   GCN CIRCULAR
NUMBER:  31361
SUBJECT: GRB220101A: optical afterglow detection from Konkoly Observatory
DATE:    22/01/02 00:53:01 GMT
FROM:    Jozsef Vinko at Konkoly Observator  <vinko@konkoly.hu>

J. Vinko, A. Pal, L. Kriskovics, R. Szakats, K. Vida  
(Konkoly Observatory, Hungary) report:

We observed the field of GRB220101A (Tohuvavohu et al., GCN #31347; Arimoto et al., 
GCN #31350; AGILE Ursi et al., GCN #31354) 
with the RC80 robotic telescope at Piszkesteto Station of Konkoly
Observatory on 2022 Jan 01  starting at 21:32:18 UT. A series of 5x300 sec
frames were collected through Sloan r'- and i' bands. The bright optical afterglow
(Kuin & Tohuvavohu, GCN #31351; Fu et al., GCN #31353; Hentunen et al., GCN
#31356; Perley, GCN #31357; Ugarte Postigo et al. GCN #31358; Fynbo et al. GCN #31359)
is clearly detected on the stacked frames with the following magnitudes, calibrated
via nearby PS1 stars:

Date         UT-middle   t-T0(hr)  Exp(s)   r'(AB-mag)       i'(AB-mag)
2022-01-01   21:52:52    16.73     5x300    19.81 +/- 0.12   18.67 +/- 0.14