{
  "bibcode": "2021GCN.30748....1S",
  "body": "R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (U. of the Virgin Islands/College of Marin) report on behalf of a larger collaboration:\n\nWe observed Swift GRB 210901A (Laha, et al., GCN 30746) with the LCO 1-m Sinistro instrument at the South African Astronomical Observatory site, on September 1, from 17:14 to 17:36 UT (corresponding to 2.17 to 2.53 hours from the GRB trigger time) with the Bessel R and I filters.\n\nWe performed a series of 3x300s exposures in R and I. In the XRT detection region (Laha, et al., GCN 30746) no optical counterpart could be detected down to the following upper limits, calculated using the USNO-B.1 catalog as reference:\n\nR>21.55\n\nI>21.16\n\nThese magnitudes are not corrected for galactic extinction.\n\nR.S. is funded by NSF AST grant #1831682",
  "circularId": 30748,
  "createdOn": 1630526551000,
  "email": "robert.strausbaugh@uvi.edu",
  "subject": "GRB 210901A: LCO Optical Upper Limit",
  "submitter": "Robert Strausbaugh at U. of the Virgin Islands  <robert.strausbaugh@uvi.edu>",
  "eventId": "GRB 210901A"
}