{
  "bibcode": "2021GCN.30337....1J",
  "body": "Martin Jelinek, Jan Strobl, Rene Hudec and Cyril Polasek (ASU CAS Ondrejov,\nCZ), report:\n\nWe observed the Swift-improved localization (Tohuvavohu et al. GCN 30325,\nPerri et al. GCN 30329) of the GBM-detected GRB 210626A (Fermi GBM Team,\nGCN 30323) with the 50 cm robotic telescope (D50) of Ondrejov observatory\nin Czech Republic. We obtained a set of 120 s Sloan-i' exposures starting\nat 21:10 UT, i.e.  0.5386 d after the initial trigger.\n\nThe magnitude limit of our 34 x 120 s image with a mean time T-T0 0.5626 d\npost burst is i' > 21.2 (AB). The XRT (Perri et al. GCN 30329) error box\ndoes not appear completely clean in the image, there is a noise fluctuation\nor possibly a candidate at the level of i' = 21.3 +/- 0.4. While we mention\nthis, we also note that this is in a light halo of a nearby bright star, so\nartefacts of this kind may not be excluded.",
  "circularId": 30337,
  "createdOn": 1624874356000,
  "email": "martin.jelinek@asu.cas.cz",
  "subject": "GRB 210626A: Ondrejov D50 optical limit",
  "submitter": "Martin Jelinek at Astro.Inst-AVCR,Ondrejov  <martin.jelinek@asu.cas.cz>",
  "eventId": "GRB 210626A"
}