{
  "bibcode": "2021GCN.30674....1B",
  "body": "M. Blazek, D. A. Kann (both HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/\nIAA-CSIC, DARK/NBI), C. C. Thoene, J. F. Agui Fernandez (both HETH/IAA-CSIC)\nreport:\n\nWe observed the location of the Swift GRB 210820A (Beardmore et al., GCN\n#30664) with 2-m Liverpool Telescope located in La Palma, Canary Isands,\nSpain. We obtained 15 x 60 s images beginning 2021-08-21 03:29:30 UT. In\na stack of all images, centered at 0.4175 days after the GRB, no source is\ndetected at the UVOT position. Measured against three nearby SDSS stars, we\nderive an upper limit of r' > 21.1 mag. This agrees with the non-detections\nreported by Lipunov et al. (GCN #30666), Fu et al. (GCN #30669)., and Zhu et\nal. (GCN #30670).",
  "circularId": 30674,
  "createdOn": 1629567040000,
  "email": "alf@iaa.es",
  "subject": "GRB 210820A: LT optical upper limit",
  "submitter": "Martin Blazek at HETH/IAA-CSIC  <alf@iaa.es>",
  "eventId": "GRB 210820A"
}