[vsnet-grb-info 27454] GRB 210222B: FRAM-ORM afterglow detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29557
SUBJECT: GRB 210222B: FRAM-ORM afterglow detection
DATE:    21/02/23 15:53:50 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 alert of GRB210222B (Gropp et al. GCNC 29545, Marrocchesi et al.
GCNC 29553), obtaining a series of 20 s unfiltered images starting at
22:38:21.1 UT, i.e. 55.1s post trigger.

We clearly detect the source reported by other telescopes (Hu et al. GCNC
29546, Strausbaugh et al. GCNC 29547, Mong et al. GCNC 29548, Perley GCNC
29549, Agui Fernandez et al. GCNC 29552, and Lipunov et al. GCNC 29554). As
seen by FRAM, the brightness of the object reached a maximum of about
R(Vega) ~ 15.5, similarly to the value of BOOTES, and then slowly changed
to a decay with an index alpha = ~1.1.

Would the decay stay at this rate, the afterglow may have a brightness of
R~22.0 24h post trigger.