{
  "bibcode": "1999GCN...275....1S",
  "body": "D. A. Smith, A. Levine, and R. Remillard (MIT), on behalf of the\nRXTE/ASM team at MIT and NASA/GSFC, K. Hurley (UCB), on behalf of the\nUlysses GRB team, and S. Barthelmy (NASA/GSFC) report:\n\nGRB 990308 was detected by the All-Sky Monitor on RXTE during a 90-s\nobservation that began at MJD 51245.218333 (03/08/99 05:14:24 UTC).\nThis burst was also observed by BATSE (Trigger #7457), and the BATSE\ntrigger time was 05:15:07 UTC.  At this time, SSC 3 of the ASM (the\ncamera aligned with the rotation axis of the ASM assembly) observed an\ninterval of enhanced count rates that lasted until the end of the\nobservation.  The light curve of the event was highly variable, with a\nmean 1.5-12 keV flux of about 400 mCrab.  SSC 3 has lost the use of\nfour of its eight resistive anodes over its the three years of\noperation, but we could still localize this GRB with the remaining\nanodes to a 10 deg by 6.6 arcmin error box (full-width at 90%\nconfidence, including estimates of both statistical and systematic\neffects), centered at R.A. = 182.761832, Decl. = +4.282319 (J2000) and\nrotated 51.2 deg east from north.\n\nGRB 990308 was also detected, very weakly, by Ulysses, and it was\ntherefore possible to obtain an IPN annulus by triangulation of burst\narrival times at Ulysses and BATSE.  This annulus is centered at\nR.A. = 154.0761 degrees, Decl. = -9.6383 degrees, with a radius of\n35.583 degrees, and a 3 sigma half-width of 0.399 degrees.  This\nannulus is based on preliminary data, but we do not expect it to\nimprove much, if at all.\n\nThe IPN annulus and the ASM error box cross each other, yielding a\njoint error box 48 arcmin by 6.6 arcmin.  The corners of this box lie\nwithin the BATSE LOCBURST error circle, and their celestial\ncoordinates are:\n\nR.A.(J2000)  Decl. (J2000)\n186.142867     +6.921870\n186.091377     +7.021754\n185.502582     +6.412172\n185.451355     +6.512323\n\nThis position was still in the FOV of SSC 3 after its 6-deg rotation,\nand examination of the instrument response at the center of the joint\nerror box yields a ~4-sigma detection of a ~50 mCrab flux (1.5-12\nkeV), averaged over the next 90-s ASM observation (56-146 s after the\nburst trigger).  This is an average of less than 2 c/s in the\ntime-series data during this observation, which shows an average total\ncount rate of 27 c/s, so it is not possible to directly measure the\nburst behavior on any shorter time-scales.  By the second observation\nafter the burst (t=152-242 s), the average flux had fallen below 30\nmCrab (3-sigma upper limit). \n\nFigures showing localizations of GRB 990308, as well as the time-\nseries data from the first ASM observation, can be seen on the WWW at\n\nhttp://xte.mit.edu/grb/trig7457.24/web_trig7457_24.html\n\nThis report may be cited.",
  "circularId": 275,
  "createdOn": 921440612000,
  "email": "dasmith@space.mit.edu",
  "subject": "ASM/IPN error box for GRB 990308 (BATSE #7457)",
  "submitter": "Don Smith at MIT  <dasmith@space.mit.edu>",
  "eventId": "GRB 990308"
}