{
  "bibcode": "2005GCN..3304....1R",
  "body": "E.S. Rykoff (U Mich), S.A. Yost (U Mich), H. Swan (U Mich) report on \nbehalf of the ROTSE collaboration:\n\nROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB \n050421 (Swift trigger 115135), producing images beginning 9.7 s after \nthe GCN notice time. An automated response took the first image at \n04:12:58.8 UT, 67.2 s after the burst, under good conditions. These \nobservations were affected by the bright moon. We took 10 5-sec, and 350 \n20-sec eposures. These unfiltered images are calibrated relative to USNO \nA2.0 (R).\n\nComparison to the DSS (second epoch) reveals no new sources within the \n3-sigma BAT error circle including the 3-sigma XRT error circle (GCN \n3301). Individual images have limiting magnitudes ranging from \n16.49-17.34. In particular, we set a limit of magnitude 16.49 in a \nsingle 5 s exposure, starting 67.1 s after the burst. Coadding images \ninto sets of 10 reveals no new sources down to limits of 17.8 (t0+61.7s \n- t0+130.7s) and 18.4 (t0+144s - t0+431s)",
  "circularId": 3304,
  "createdOn": 1114097082000,
  "email": "erykoff@umich.edu",
  "subject": "GRB 050421: ROTSE-III Optical Limits",
  "submitter": "Eli Rykoff at U of Michigan/ROTSE  <erykoff@umich.edu>",
  "eventId": "GRB 050421"
}