{
  "bibcode": "2000GCN...700....1K",
  "body": "GRB000528: follow-up X-ray measurements and update of IPN annulus \n\nE. Kuulkers, L. Kuiper, J.J.M. in 't Zand, J. Heise (Space Research\nOrganization Netherlands), L.A. Antonelli (Osservatorio Astronomico di Roma),\nK. Hurley (University of California, Berkeley), L. Salotti (ASI, Rome),\nM. Stornelli, G. Celidonio (Telespazio, Rome), E. Costa, M. Feroci, \nG. Gandolfi (IAS-CNR, Rome), F. Frontera (ITESRE-CNR, Bologna, and University\nof Ferrara) L. Nicastro (IFCAI-CNR, Palermo), T. Cline (NASA Goddard Space\nFlight Center), E Mazets (Ioffe Physici-Technical Institute, St. Petersburg), \nC. Guidorzi, and E. Montanari (University of Ferrara) report:\n\nThe BeppoSAX narrow-field instruments observed the region of GRB000528 twice:\nfrom May 28.71 to May 29.57 UT (TOO1, 8.3-28.9 hours after the burst) and\nfrom May 31.65 to June 1.49 (TOO2). The total exposure time obtained with\nthe Medium-Energy Concentrator Spectrometers (MECS) is 58 ksec. Two X-ray\nsources close to one another were detected in the field, one at\nR.A. = 10h 45h 28m, Dec. = -33d 58' 14\" (J2000.0), which we designate as\n1SAX J1045.5-3358 (object 1 in GCN 683), and the other at R.A. = 10h 45m 08s,\nDec. = -33d 59' 26\", which we designate as 1SAX J1045.1-3359 (object 2 in GCN\n683). Both sources have a conservative positional error of 1.5'. Object 2 is\ninside the WFC error region (GCN 677) while the centroid of object 1 is 2.5\narcmin outside that region. We note that a bright and archival radio source\nhas been reported coincident with object 1 (GCN 686). A refined IPN analysis\nusing Ulysses, BeppoSAX, and Konus data indicates that object 1 is far less\nconsistent with the IPN annuli than object 2. The countrates for object 1\nin MECS units 2 and 3 combined are (2.10+/-0.44)E-3 and (1.21+/-0.36)E-3 c/s\nfor TOO1 and TOO2 respectively and for object 2 (2.40+/-0.46)E-3 and\n(0.65+/-0.32)E-3 c/s. Object 2 shows the strongest fading. Based on all\npieces of information, we identify object 2 (1SAX J1045.1-3359) as the\nlikely X-ray afterglow of GRB 000528.\n\nFor maps of the error regions, see URL http://wfc.sron.nl/GRB000528/\n\nNeither the WFC nor the GRBM observed the delayed emission 600 s after\nthe burst (GCN 681); the source was unocculted at this time, and this\nemission would have been detected with high significance if it had\noriginated from this source.  We conclude that this emission was either\nsolar in origin, or possibly from a different GRB.\n\nThis message may be cited.",
  "circularId": 700,
  "createdOn": 960922368000,
  "email": "jeanz@sron.nl",
  "subject": "GRB000528: follow-up X-ray measurements and update of IPN annulus",
  "submitter": "Jean int Zand at SRON  <jeanz@sron.nl>",
  "eventId": "GRB 000528"
}