{
  "bibcode": "2003GCN..2153....1S",
  "body": "Smith, D. A., Rykoff, E. S., McKay, T. A. report on behalf of the ROTSE\ncollaboration:\n\nThe ROTSE-IIIa robotic telescope at Siding Springs Observatory, NSW, responded\nautomatically to the two HETE alerts for this burst, in each case beginning a\n~45 minute sequence of unfiltered observations within six seconds of the alert\ntime stamp, the first of which was 238 s after the burst.  Each image sequence\nbegan with 10 5-s images and then continued with 90 20-s images.\n\nThe 20-s images reached typical limiting magnitudes of 17.5 calibrated against\nthe USNO A2.0 catalog in R band, while the 5-second images reached\n16.9. Sensitivity was degraded by the full moon.  Automated software searched\nthese frames for variable sources not in the USNO catalog and failed to\nidentify any counterpart candidates.  In particular, no source was initially\ndetected at the location of the optical counterpart reported by Price et al.\n(GCN Circ. 2148).\n\nCo-addition of multiple frames, however, yielded significant detections of the\noptical transient.  We co-added our 200 observations into groups of ten, and\nfound that from 10:05:23 to 10:50:05, and again from 11:43:07 to 12:20:42, we\nmeasure the transient to vary irregularly between 18.7 and 17.4, with errors of\norder 0.15 mag.  This means that from 360 s to 2.3 h after the burst, the\ntransient showed no evidence for decay, in marked contrast to other bursts that\nhave been observed at early times, such as 990123 and 021211.",
  "circularId": 2153,
  "createdOn": 1050704110000,
  "email": "dasmith@rotse2.physics.lsa.umich.edu",
  "subject": "ROTSE-III prompt optical detections of GRB 030418",
  "submitter": "Don Smith at U michigan  <dasmith@rotse2.physics.lsa.umich.edu>",
  "eventId": "GRB 030418"
}