{
  "bibcode": "2025GCN.40823....1M",
  "format": "text/plain",
  "submitter": "Alexander Moskvitin at SAO RAS <mosk@sao.ru>",
  "eventId": "GRB 250617B",
  "body": "A. Moskvitin, O. Spiridonova (SAO RAS), N. Pankov (HSE, IKI), E. Klunko (ISTP),  A. Pozanenko (IKI) report on behalf of GRB follow-up and IKI-GRB-FuN collaborations.\n\nWe observed the field of the GRB 250617B (Page et al., GCN 40760; \nFermi GBM team, GCN 40763;  Bala and Meegan, GCN 40766; Osborne et al., GCN 40767; Williams et al., GCN 40773; Laha et al., GCN 40812) at the redshift of z = 1.396 (Corcoran et al., GCN 40776) with the 1.5-meter AZT-33IK telescope of Mondy observatory on 2025-06-23 and with the 1-m telescope Zeiss-1000 of the SAO RAS on 2025-06-24.\n\nThe OT (Page et al., GCN 40760; Moskvitin et al., GCN 40761; \nJelinek et al., GCN 40762; Grossan et al., GCN 40771; Ma et al., GCN 40772; \nAntier et al., GCN 40775; Corcoran et al., GCN 40776; Turpin et al., GCN 40777; \nSiegel and Page, GCN 40778; Pankov et al., GCN 40783; Gendreau-Distler et al., \nGCN 40789; Calapai, GCN 40804; also detected in NIR by Schneider et al., GCN 40774) is marginally detected in AZT-33IK stacked image and clearly detected in Zeiss-1000 stacked image. Preliminary results are as following.\n\nDate       UT start t-T0      Exp.   Filter OT Err.  UL   telescope\n                    (mid, days) (s)                  (3 sigma)\n2025-06-23 16:37:49 5.84791   45*120 R      22.9 0.4 22.7 AZT-33IK     \n2025-06-24 22:44:03 7.09417   12*300 Rc     23.4 0.2 23.9 Zeiss-1000\n\nThis photometry is based on the USNO-B1.0 stars given in Moskvitin et. al, (GCN 40761) and has not corrected for the Galactic extinction.",
  "circularId": 40823,
  "createdOn": 1750864236223,
  "submittedHow": "web",
  "subject": "GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24"
}