{
  "bibcode": "2000GCN...832....1P",
  "body": "L. Piro (BeppoSAX Mission Scientist, IAS/CNR Roma) & L. A. Antonelli (OaR)\nreport on behalf of the BeppoSAX team:\n\nA BeppoSAX TOO observation of GB000926  started on Sept. 29.00, i.e.\n2 days after the GRB and lasted for 12 hrs.\nEffective exposure times were MECS(1.6-10 keV): 20 ksec, LECS(0.1-10\nkeV):5 ksec.\n\nWe confirm the relatively bright unknown source identified as the X-ray\nafterglow by Piro (GCN 812)\n\n\nThe revised position is:\n\nRA(2000)=17h 04m 07s Decl.(2000)= +51 47' 18\"\n\nwith an error radius of 50\", consistent with the previous preliminary\nposition distributed in GCN 812 and with the optical counterpart\n(Gorosabel et al. GCN 803, Dall et al. GCN 804, Halpern et al. GCN 806).\n\n\nThe average flux of the source in the MECS(1.6-10 keV) is (4.1+/-0.6)\n10^-3 cts/s, corresponding to a F(1.6-10 keV)=(4.8+-0.7) 10^-13 erg/cm2/s.\nThe spectrum is consistent with a power law with photon index=(1.9+/-0.7)\nand absorption by our Galaxy (NH=2.7 10^20 cm-2).\n\nThe BeppoSAX observation occured in coincidence with the break of the\noptical light curve reported e.g by Fynbo (GCN820), Veillet (GCN 823) and\nHalpern et al (GCN824). In the X-ray band the source exhibits a\nsubstantial decay, decreasing by a factor of (1.7+/-0.5) in 6 hours. This\nwould correspond to a power law decay F= c(T-T0)^d_X (where T0=26.99)\nwith slope d_X=-4.3+/-1, i.e. steeper that that measured in the\noptical after the break (d_O=-2.5+/-0.2,  Halpern et al., GCN 824).\nThis behaviour is not immediately consistent with a jet-expansion, that\npredicts d_X=d_O. Chandra data, taken few hours after the end of the\nBeppoSAX observation, shall be crucial in confirming the X-ray light\ncurve.",
  "circularId": 832,
  "createdOn": 970776005000,
  "email": "piro@ias.rm.cnr.it",
  "subject": "GRB000926: X-ray afterglow by BeppoSAX. Refined analysis",
  "submitter": "Luigi Piro at IAS/CNR Frascati  <piro@ias.rm.cnr.it>",
  "eventId": "GRB 000926"
}