{
  "subject": "GRB 230307A: iTelescope optical upper limit (likely)",
  "eventId": "GRB 230307A",
  "bibcode": "2023GCN.33635....1R",
  "createdOn": 1681659079000,
  "circularId": 33635,
  "submitter": "Filipp Dmitrievich Romanov at Amateur astronomer  <filipp.romanov.27.04.1997@gmail.com>",
  "email": "filipp.romanov.27.04.1997@gmail.com",
  "body": "On 2023-03-09 I observed the field of GRB 230307A (Fermi GBM team, GCN\nCirc. 33405) remotely using the telescope T17 (0.43-m f/6.8 reflector\n+ CCD) of iTelescope.Net in Siding Spring Observatory (Australia). Ten\nimages with exposures of 300 seconds and Ic filter (Astrodon\nJohnson-Cousins Ic) were obtained, the midtime of the stacked image is\n10:52:40.7 UT (1.8 d. after the trigger). I did not detect a clear\noptical afterglow near the Swift-XRT position (Burrows et al., GCN\nCirc. 33465), but in this area in the stacked image there is what I\ncan consider a noise (SNR <2), but I do not exclude that it may be\nfaint afterglow near the upper limit of about 20 magnitudes in this\nband."
}