[vsnet-grb-info 27022] GRB 201221D: FRAM-ORM optical limit

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29125
SUBJECT: GRB 201221D: FRAM-ORM optical limit
DATE:    20/12/22 10:25:06 GMT
FROM:    Martin Jelinek at Astro.Inst-AVCR,Ondrejov  <martin.jelinek at asu.cas.cz>

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

report:

The 25cm robotic telescope FRAM-ORM at La Palma (Spain) reacted robotically
to the Swift alert of GRB201221D (Page et al., GCNC 29112 and Evans et al.
GCNC 29113, GCNC 29119 and 29124), obtaining a series of 20s unfiltered
images starting at 23:07:11.9 UT, i.e. 37.6s post trigger.

We do not detect any new or strongly variable source neither in single
images (detection limit R>~16.9) nor in a combined 40x20s frame (mean exp
time 560s post trigger, with a limit R>~18.5). While we analysed the entire
25'x25' field of view centred at the XRT localization, we did pay a special
attention to the location of the candidate afterglow mentioned by Malesani
& Knudstrup (GCNC 29117) with a negative outcome.