TITLE:   GCN CIRCULAR
NUMBER:  29099
SUBJECT: GRB 201221A: FRAM-Auger optical limit
DATE:    20/12/21 08:29:10 GMT
FROM:    Martin Jelinek at Astro.Inst-AVCR,Ondrejov  <martin.jelinek@asu.cas.cz>

Martin Jelinek, Jan Strobl (ASU CAS Ondrejov, CZ),
Martin Masek, Petr Janecek, Sergey Karpov, Jakub
Jurysek, Jan Ebr, Ronan Cunniffe, Petr Travnicek and
Michael Prouza (Institute of Physics, Prague, CZ)

report:

The 30cm robotic telescope FRAM-Auger in Malargue (Argentina) reacted
robotically to the Swift/BAT alert of GRB201221A (Page et al., GCNC 29096,
Evans et al., GCNC 29097), starting with a series of 20 s R-band images at
07:10:13 UT, i.e. 72 s post trigger.

We do not detect any new or strongly variable source at or around the
reported gamma-ray errorbox in single frames nor in a combined 20 x 20 s
image spanning the period from 1.2 min to 12.1 min after the initial
trigger. The combined exposure has a 3-sigma limiting magnitude R(Vega) ~
17.5.