{
  "bibcode": "2025GCN.39730....1P",
  "format": "text/plain",
  "subject": "GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits",
  "submittedHow": "web",
  "createdOn": 1742023293833,
  "eventId": "GRB 250226A",
  "body": "N. Pankov (HSE, IKI), E. Klunko (ISTP), A. Novichonok (KIAM), I. Nikolenko (INASAN), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN:\n\nWe performed optical observations of the field of GRB 250226A (The Fermi GBM team, GCN 39479; V.Lipunov et. al, GCN 39481; Jiang et. al, GCN 39482; An et. al, GCN 39486; Zhu et. al, GCN 39487; Magnani et. al, GCN 39488; Li et. al, GCN 39489; Li et. al, GCN 39492; Aryan et. al, GCN 39509; Zou et. al, GCN 39511; Jiang et. al, GCN 39513; Li et. al, GCN 39514; Junjie-Jin et. al, GCN 39515; Thakur et. al, GCN 39518; Poidevin et. al, GCN 39524; Pathak et. al, GCN 39530; Pankov et. al, GCN 39539; Pankov et. al, GCN 39540; Svinkin et. al, GCN 39542; Tanasan et. al, GCN 39554) in the Rb filter with 1-meter Zeiss-1000 telescope of the Koshka Observatory (INASAN), and in the R-filter with 1.5-meter AZT-33IK telescope of Sayan Solar Observatory (Mondy). The observations began on 2025-02-28 23:27:51 UT, i.e. ~2.75 days since trigger at Koshka. We do not detect the optical counterpart in the stacked images from both telescopes. The preliminary upper limits are as follows:\n\nDate       UT start  t-T0         Exp.    Filter  UL(3sigma)\n                     (mid, days)  (s)\n2025-02-28 23:27:51  2.75236      47*180  Rb      22.1\n2025-03-01 20:06:19  3.60304      57*120  R       23.8\n\nRef. stars\nUSNO-B1.0\nRA Dec R2\n14:57:12.82 +20:57:33.04 15.73\n14:57:12.66 +21:00:25.03 15.74\n14:56:52.84 +21:00:58.82 14.86\n\nThe photometry is based on nearby stars from the USNO-B1.0 catalog (see above) and has not been corrected for the Galactic extinction.",
  "circularId": 39730,
  "submitter": "Nicolai Pankov at HSE, IKI RAS <colinsergesen@gmail.com>"
}