{
  "eventId": "GRB 250404A",
  "circularId": 40090,
  "submitter": "Alexei Pozanenko at IKI, Moscow <grb.alex@gmail.com>",
  "submittedHow": "email",
  "subject": "GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit",
  "createdOn": 1743944706248,
  "body": " N. Pankov (HSE), A.N. Tarasenkov (INASAN), A. Pozanenko (IKI) report on\nbehalf of IKI GRB-FuN:\n\nWe observed GRB 250404A / EP250404a (Fermi GBM team, GCN 40050; Hu et al.,\nGCN 40051; Frederiks et al., GCN 40087) with RC500 telescope of the\nINASAN-Kislovodsk observatory. The optical counterpart (Jiang et al., GCN\n40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Zhu et al.,\nGCN 40061; Konno et al., GCN 40063; Odeh et al., GCN 40064; He et al., GCN\n40069; Pérez-Fournon et al., GCN 40071; Jelinek et al., GCN 40072;\nRakotondrainibe et al., GCN 40073; Taguchi et al., GCN 40074; Brivio et\nal., GCN 40075; Ruocco et al., GCN 40076; Martin-Carrillo et al., GCN\n40080; Pavoni et al., GCN 40083; Li et al., GCN 40084; Yin et al., GCN\n40085; Pankov et al., GCN 40086; Chen et al., GCN 40088;) is not detected\nstarting on 2025-04-04 (UT) 21:10:11. Preliminary upper limit of the\nstacked image is the following\n\nDate UT start t-T0 Filter Exp. OT Err. UL(3sigma)\n(mid, days) (s)\n\n2025-04-04 21:10:11 0.33362 R 70*120 n/d n/d 20.1\n\nThe photometry is based on nearby USNO-B1.0 stars.\n",
  "bibcode": "2025GCN.40090....1P"
}