{
  "submitter": "Alexei Pozanenko at IKI, Moscow <grb.alex@gmail.com>",
  "createdOn": 1774131694340,
  "subject": "GRB 260310A: continued optical observation at Mondy",
  "eventId": "GRB 260310A",
  "circularId": 44073,
  "bibcode": "2026GCN.44073....1P",
  "submittedHow": "email",
  "body": "N. Pankov (IKI), A. Volnova (IKI), E. Klunko (ISTP), A. S. Moskvitin\n(SAO RAS), O. Spiridonova (SAO RAS), A. Pozanenko (IKI) report on\nbehalf of GRB IKI FuN.\n\nWe continued observation the GRB260310A/AT2026fgk detected by\nFermi/GBM (Fermi GBM team, GCN 43951) and AstroSat (Salunke et al.,\nGCN 43958) with AZT-33IK telescope of Mondy observatory. We obtained\nseries in B and R filters on 2026-03-21.\n\nThe OT discovered by GOTO (O'Neill et al. 2026, TNS Discovery Report\n294132) and observed earlier (Konno et al., GCN 43974; Hinds et al.,\nGCN 43977; Lipunov et al., GCN 43978;Martin-Carrillo et al., GCN\n43979; Méndez et al., GCN 43980;de Ugarte Postigo et al., GCN 43984;\nHsu et al., GCN 43986; Pursiainen et al., GCN 43990; Becerra et al.,\nGCN 43991; Li et al., GCN 43993; Jayaraman et al., GCN 43994; Stein et\nal., GCN 43996;Martin-Carrillo et al., GCN 44000; Moreno Méndez et\nal., GCN 43980; Becerra et al., GCN 43991; Li et al., GCN 43993; Stein\net al., GCN 43996; Watson et al., GCN 44001; Lai et al., GCN 44002;\nIzzo et al., GCN 44003; Brivio et al., GCN 44004; Moskvitin et al.,\nGCN 44006; Romanov, GCN 44020; Brosio et al., GCN 44021; Pawar et al.,\nGCN 44022; Belkin et al., GCN 44043; Li et al., GCN 44044; Gupta et\nal., GCN 44051; Becerra et al., GCN 44059; Volnova et al., GCN 44060;\nBusmann et al., GCN 44061; Zheng t al., GCN 44065) is clearly detected\nin our images. Preliminary photometry is the following\n\nDate UT_start t_mid - T0,  exp, mag, err,  filter, UL(3sigma)\n                          days                s\n\n2026-03-21 16:35:57 11.48526 30*120 B 20.19 0.04 23.3\n2026-03-21 16:04:50 11.46366 15*120 R 19.21 0.04 23.4\n\nThe photometry is based on the nearby calibrations stars of PS1\ncatalogue converted to B, R using the Lupton (2005) transformations.\nThe magnitudes of the AT2026fgk are not corrected for Galactic\nextinctions.\n\nThe light curve obtained from our observations and GCNs can be found\nin https://heaiki.ru/lvc/GRB260310A/GRB260310A_LC.png\nWe can assume that the light curve becomes steeper 9 days after long\nlasting plateau phase\n"
}