GCN Circular 28615

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 GRB201013A (Page et al GCNC 28607), obtaining a series of
20 s unfiltered images starting at 03:47:01.3 UT, i.e. 31.3s post trigger.

There is a relatively bright star (R~16.3) within the errorbox of the XRT
localization. With the relatively coarse resolution of the 25 cm telescope,
direct detection of a faint object within the XRT errorbox is impossible.

We performed aperture photometry of the star. There seems to be an excess
flux of ~3.5 sigma by ~ 570 s post trigger. This is when optical afterglows
often show maxima in their
lightcurves.

We also performed image subtraction of a sum of four images obtained at the
time of the detected peak and twelve latest images of the series. The
resulting frame contains a very
weak residual towards the position of the X-ray afterglow from the star
center.

We therefore conclude that there is a slight possibility of an afterglow
peaking at R~17.0, which was outshined by a nearby star of R~16.3.