{
  "bibcode": "2021GCN.29852....1D",
  "body": "A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), D. B. Malesani (DTU\nSpace), E. Knudstrup (NOT, Aarhus Univ.) report on behalf of a larger\ncollaboration:\n\nWe observed the afterglow of GRB 210420B (Moss et al. GCN 29844;\nLipunov et al. GCN 29845; Oksanen GCN 29846; Hu et al. GCN 29847; \nSun et al. GCN 29848; Leonini et al. GCN 29851) with ALFOSC at the \n2.5 m Nordic Optical Telescope at Roque de los Muchachos Observatory \n(La Palma, Spain). The observation consisted of 3x100 s imaging in g, r \nand i bands, and 5x100 s in z-band and started at 00:13 UT.\n\nThe afterglow is well detected in individual images in all bands at\nthe following coordinates (J2000) calibrated with Gaia, and with an\nuncertainty estimated at 0.3\":\n\nR.A. = 16:57:18.00\nDec. = +42:34:12.1\n\nIn a preliminary analysis we measure the following AB magnitudes, as\ncompared with 3 field stars from the SDSS catalogue:\n\ng = 19.45 +/- 0.04\nr =  19.32 +/- 0.04\ni = 19.18 +/- 0.04\nz = 19.03 +/- 0.07",
  "circularId": 29852,
  "createdOn": 1618969360000,
  "email": "deugarte@iaa.es",
  "subject": "GRB 210420B: Multiband photometry from NOT",
  "submitter": "Antonio de Ugarte Postigo at IAA-CSIC  <deugarte@iaa.es>",
  "eventId": "GRB 210420B"
}