TITLE:   GCN CIRCULAR
NUMBER:  30404
SUBJECT: GRB 210706A: optical upper limit of Sintesz-Newton/CrAO and AS-32/AbAO
DATE:    21/07/07 13:44:19 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

N. Pankov (IKI, HSE), S. Nazarov (CrAO), R. Ya. Inasaridze (AbAO), A. 
Pozanenko (IKI), S. Belkin (IKI, HSE)  report on behalf of IKI GRB FuN:

We observed the filed of Swift/BAT-GUANO detection GRB 210706A 
(Tohuvavohu   et al., GCN 30393),  GRB 210706A also triggered Konus-Wind 
(Ridnaia et al., GCN 30403) with Sintesz-Newton 350mm f/5 telescope of 
CrAO observatory and AS-32 telescope of Abastumani observatory (AbAO). 
Observation started on 2021-07-06 (UT) 22:52:40 and consist of 6 images 
of 300 s exposure in Clear filter (Sintesz-Newton) and in R-filter (UT) 
2021-07-06 (UT) 20:23:40 (AS-32). In bothe telescopes we cover the whole 
localization region of Swift/BAT-GUANO (Tohuvavohu   et al., GCN 30393). 
We find no new optical sources in either of the two XRT candidates 
(https://www.swift.ac.uk/ToO_GRBs/00021455/). In particular no source 
was detected in XRT afterglow candidate #2 (Tohuvavohu   et al., GCN 30399).

Upper limit for of the stacked image is following

Date       UT start   t-T0    Filter Exp.     OT   err   UL(3) Telescope
                      (mid, days)       (s)

2021-07-06 20:23:40   0.50719 R      9*60    n/d  n/d    20.5  AS-32
2021-07-06 22:52:40   0.60755 Clear  6*300   n/d  n/d    21.5  Newton


The photometry is based on nearby USNO-B1.0 (R2) stars.

Our non-detections is consistent with results of GROWTH-India Telescope 
(Kumar  et al., GCN 30402).