TITLE:   GCN CIRCULAR
NUMBER:  31387
SUBJECT: GRB 220101A: iTelescope optical observations
DATE:    22/01/04 19:11:01 GMT
FROM:    Filipp Dmitrievich Romanov at Amateur astronomer  <filipp.romanov.27.04.1997@gmail.com>

I observed the field of GRB 220101A (Tohuvavohu et al., GCN Circ.
31347) using remote telescope T21 (0.43-m f/6.8 reflector + CCD +
f/4.5 focal reducer) of iTelescope.Net in Observatory New Mexico Skies
at Mayhill (New Mexico, USA). Four images (with exposures 300 seconds,
BINx1) were obtained with Ic filter on 2022-01-04 from 01:29:50 to
01:51:05 UTC.

I detected faint (SNR ≈ 3) optical afterglow with UVOT position in
stacked image (mid time = 01:40:27 UTC, that is 2.854 days after the
trigger) and measured its magnitude from comparison to magnitudes of
nearby stars from the SDSS Photometric Catalogue, Release 12 (Alam et
al., 2015), transformed to Ic by Lupton's (2005) formulas.

Measured magnitude (was not corrected for Galactic extinction) = 19.4
+/- 0.4 Ic. Stacked image available here:
https://www.flickr.com/photos/filipp-romanov/51800218870

I also observed the field of GRB 220101A remotely with telescope T18
(0.32-m f/8.0 reflector + CCD) in AstroCamp observatory (Nerpio,
Spain). I did not detect the source (magnitude limit of about 19 R) in
a 300-sec image taken with a red filter, started on 2022-01-02 at
18:40:52 UTC.

F. D. Romanov.