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GCN Circular 32889

Subject
GRB 221028A: CrAO/ZTSh optical upper limit
Date
2022-10-29T20:04:27Z (a year ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Belkin (IKI), N. Pankov (HSE),  V. Rumyantsev (CrAO), A. Pozanenko 
(IKI)  report on behalf of IKI GRB FuN:

We observed the GRB 221028A  (Lien et al., GCN 32874; Ursi et al., GCN 
32885) with ZTSh 2.6m telescope of CrAO observatory starting on Oct. 28 
(UT) 19:38:37.  We do not detect any optical object within XRT 
localization (Lien et al., GCN 32874). This is consistent with reported 
  non-detections   (Hu et al., GCN 32878; Kumar et al., GCN 32876; 
Lipunov et al., GCN 32879; Strausbaugh et al., GCN 32881; Niwano et al., 
GCN 32883; Kumar  et al., GCN 32886;  Watson   et al., GCN 32888).

Preliminary photometry of the field in a combined image is following

Date       UT start   t-T0    Filter Exp.     OT      err    UL(3sigma)
                      (mid, days)       (s)
2022-10-28 19:38:37   0.27233 R      10*120   n/d     n/d    20.7

The photometry is based on several nearby USNO-B1.0 (R2) stars
USNO-B1.0
RA DEC R2
20:56:40.7621 +41:04:57.000 15.60
20:56:51.9768 +41:04:22.922 17.21
20:57:00.0629 +41:02:55.072 16.04
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