{
  "bibcode": "2007GCN..6761....1Y",
  "body": "F. Yuan, E.S. Rykoff (U Mich), report on behalf of the ROTSE collaboration:\n\nROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB \n070810A (Swift trigger 287364;  Cummings, et al., GCN 6733), and \ndetected the optical counterpart (Swan, et al., GCN 6734).\nThe initial aperture photometry reported in GCN 6734 was biased due to \ncontamination from the nearby star.\nWith a reference image taken 6 days after the burst, we were able to \nsubtract the nearby star and obtain better estimate of the OT \nbrightness with PSF fitting. Our refined analysis shows the OT at 18.0 \n� 0.2 mag (unfiltered images, calibrated relative to USNO-B1.0 R) \nbetween 1607s and 2290s after the burst.\n\nstart UT       end UT        mag\n-------------------------------------\n02:38:39.5   02:50:02.3    18.0+/-0.2\n03:13:15.7   03:24:39.0    18.5+/-0.2\n\n\nThe OT faded with a decay index 0.7 �0.2 in the next 40 minutes before \ndropping below our detection threshold. This decay index is \nsignificantly shallower than seen at later time in Keck photometry \n(Perley, et al., GCN 6757), implying a light curve break between 1.2 hr \nand 4 hr after the burst.",
  "circularId": 6761,
  "createdOn": 1187310267000,
  "email": "yuanfang@umich.edu",
  "subject": "GRB 070810A: ROTSE-III Refined Analysis",
  "submitter": "Fang Yuan at ROTSE  <yuanfang@umich.edu>",
  "eventId": "GRB 070810A"
}