TITLE:   GCN CIRCULAR
NUMBER:  29570
SUBJECT: GRB 210226A: Ondrejov BART/SBT optical limit
DATE:    21/02/26 08:05:59 GMT
FROM:    Martin Jelinek at Astro.Inst-AVCR,Ondrejov  <martin.jelinek@asu.cas.cz>

Martin Jelinek, Jan Strobl, Rene Hudec and Cyril Polasek (ASU CAS Ondrejov,
CZ), report:

The 0.2 m Small Binocular Telescope (BART/SBT) of Ondrejov observatory in
Czech republic reacted robotically to the alert of GRB 210226A (Beardmore
et al, GCNC 29568), obtaining a series of 12 s unfiltered images starting
at 04:54:55.8 UT, i.e. 659 s post trigger.

We do not detect any new source within the XRT errorbox neither in single
images (3-sigma limit r'(AB) > ~14.0) nor in a combined 30 x 12 s frame
(mean exp time 1033 s post trigger, 3-sigma limit r'(AB) > ~15.8) as
calibrated against the Atlas catalog (Tonry et al. ApJ 867, 105, 2018).