{
  "bibcode": "2021GCN.29747....1L",
  "body": "Simone Leonini, M. Conti, P. Rosi and L.M. Tinjaca Ramirez (Montarrenti Observatory, Siena, Italy) report:\n\nWe observed the field of GRB210402A (Swift trigger 1040123, Fermi trigger 639093861, K.L. Page et al., GCN Circ. 29743) with the automatic 0.53m RC telescope + U47 detector at Montarrenti Observatory (Siena, Italy, IAU code C88).\n\nThe observations were started at 2021-04-02 22:48:18 UT (18 minutes post-burst) stacking 4 unfiltered CCD exposures of 40s each.\n\nWe have not found optical transient within the error-box given.\nMag. upper limit R = 20.10+/-0.19\n\nMagnitudes were obtained using Astrometrica software using USNO-B1 catalogue and are not corrected for galactic extinction.",
  "circularId": 29747,
  "createdOn": 1617434261000,
  "email": "s.leonini@iol.it",
  "subject": "GRB 210402A: Montarrenti Observatory upper limit",
  "submitter": "Simone Leonini at Monarrenti Obs  <s.leonini@iol.it>",
  "eventId": "GRB 210402A"
}