{
  "bibcode": "2021GCN.29883....1V",
  "body": "J. Vinko (Konkoly/ELTE/U Szeged), L. Kriskovics, R. Szakats, A. Pal and K. Vida (Konkoly)\nreport on behalf of the \"Transient Astrophyical Objects\" project:\n\nWe observed the field of GRB 210420B (Moss et al., GCN 29833; Lien et al., GCN 29854; \nOsborne et al. GCN 29876; Stamatikos et al., GCN29879) with the 0.8m RC80 robotic telescope at Piszkesteto Mountain Station of Konkoly Observatory through SDSS r' and i' filters on \n2021 Apr 21.85 UT (MJD 59325.85, 1.07 day after the trigger). The total exposure time \nwas 1800 s in both filters. \n\nThe frames were tied to PS1-photometry of local stellar sources. We detect the optical \nafterglow (Lipunov et al., GCN 29845; Oksanen et al., GCN 29846; Hu et al., GCN 29847;\nTianrui Sun et al., GCN 29848; Leonini et al., GCN 29851; de Ugarte Postigo et al., \nGCN 29852, 29853; Watson et al., GCN 29858; Zheng et al., GCN 29861; Breeveld et al., \nGCN 29862; Stecklum et al., GCN 29863; Butler et al.,GCN 29864; Jelinek et al., GCN 29866;\nWatson, GCN 29867; Leonini et al., GCN 29872) is detected on the stacked r-band images. \nForced photometry at the position of the GRB, tied to the PS1 photometry of nearby stars, \nresulted in the following AB-magnitudes:\n\nr = 20.76 +/- 0.33 (5-sigma limit 22.18)\ni > 22.09 (5-sigma limit)",
  "circularId": 29883,
  "createdOn": 1619113997000,
  "email": "vinko@konkoly.hu",
  "subject": "GRB 210420B: follow-up photometry of the optical afterglow at Konkoly",
  "submitter": "Jozsef Vinko at Konkoly Observator  <vinko@konkoly.hu>",
  "eventId": "GRB 210420B"
}