{
  "bibcode": "2021GCN.29866....1J",
  "body": "M. Jelinek, J. Strobl, R. Hudec, C. Polasek (ASU CAS Ondrejov)\n\nreport:\n\nWe observed the position of the bright GRB 210420B (Moss et al., GCN 29833\n& Lien et al., GCN 29854) with the D50 telescope of the Astronomical\nInstitute Ondrejov, near Prague, Czech  Republic. We performed a series of\n120 s unfiltered exposures starting 21:10 UT, between 2.6 and 4.9 h after\nthe trigger.\n\nThe optical afterglow (Lipunov et al., GCNC 29845; Oksanen et al., GCNC\n29846; Hu et al., GCNC 29847; Tianrui Sun et al., GCNC 29848; Leonini et\nal., GCNC 29851; de Ugarte Postigo et al., GCNC 29852; de Ugarte Postigo et\nal., GCNC 29853; Watson et al., GCNC 29858; Zheng et al., GCNC 29861;\nBreeveld et al., GCNC 29862; Stecklum et al., GCNC 29863 and Butler et al.,\nGCNC 29864) is clearly detected in single 120 s images, at least at the\nbeginning of the series.\n\nWe can confirm a decaying nature of the object - the afterglow faded > 0.4\nmag during the course of our observations, providing an alpha decay of 0.69\n+- 0.17.",
  "circularId": 29866,
  "createdOn": 1619019136000,
  "email": "martin.jelinek@asu.cas.cz",
  "subject": "GRB 210420B: Ondrejov D50 optical afterglow detection",
  "submitter": "Martin Jelinek at Astro.Inst-AVCR,Ondrejov  <martin.jelinek@asu.cas.cz>",
  "eventId": "GRB 210420B"
}