TITLE:   GCN CIRCULAR
NUMBER:  30888
SUBJECT: GRB 210919A: iTelescope T-11 upper limits
DATE:    21/09/27 09:23:47 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

K. Hasuda, T. Sakamoto (AGU)

We observed the field of GRB 210919A detected by Swift
(Tohuvavohu et al., GCN Circ. 30846) with the iTelescope.Net
(http://www.itelescope.net) T11 (Planewave 20" CDK) telescope
located at the New Mexico Skies Observatory (NM, USA).
59 images of 60 sec exposures were taken in the R filter
starting from September 21 on 10:04:47 (UT) about 2.4 days after
the trigger and stopped on 11:26:12 (UT).  We further obtained
60 images of 60 sec exposures in the R filter starting from
September 22 on 10:01:34.4 (UT) and stopped on 11:27:50 (UT).

We do not detect the optical afterglow both in the individual
images and the stacked image at the XRT position
(Goad et al., GCN Circ. 30850).  The estimated five sigma
upper limits of the combined image of the first observation
(total exposure of 3540 sec) and the second observation (total
exposure of 3600 sec) are 17.8 and 19.1 using the USNO-B1 catalog.