{
  "subject": "IBAS distribution of coordinates for low significance INTEGRAL GRB triggers",
  "bibcode": "2011GCN.11766....1M",
  "createdOn": 1298564322000,
  "circularId": 11766,
  "submitter": "Sandro Mereghetti at IASF/CNR  <sandro@iasf-milano.inaf.it>",
  "email": "sandro@iasf-milano.inaf.it",
  "body": "S.Mereghetti (INAF IASF-Milano), D.Gotz (CEA-Saclay), J. Borkowski (CAMK, \nTorun), M. Beck, C.Ferrigno (ISDC, Versoix), on behalf of the IBAS \nLocalization Team announce:\n\nA new version of the IBAS Alert Distribution system is operational at the \nINTEGRAL Science Data Center. In addition to the already available \nfunctionalities, the new version distributes in real time also Alert \nPackets for low significance triggers discovered in the field of view of \nthe IBIS imager.\n\nThe new Alert Packets are called WEAK Alerts and are identified by the \nfield PKT_TYPE=6 (see http://www.isdc.unige.ch/integral/science/grb#IBAS \nfor details on the different Alert types).\n\nUsers interested to receive the Alert Packets of the new type \"WEAK\" \nshould contact the ISDC IBAS team (isdc-ibas@unige.ch).\n\nThe threshold for the distribution of the usual high significance IBAS \ntriggers remains unchanged at\n\nSIGMA= 8.0   (Alert Packets with PKT_TYPE= 3 (WAKEUP))\n\nwhile the threshold for the distribution of low significance IBAS triggers is \ncurrently set at\n\nSIGMA= 6.5   (Alert Packets with PKT_TYPE= 6 (WEAK))\n\nThis threshold corresponds to a rate of a few WEAK Alert Packets per week, \nbut it could be adjusted in the future.\n\nMany WEAK alerts will be produced by statistical fluctuations, but there \nis also a non negligible probability that some of them are due to real \nastrophysical events. In most cases it is not possible to recognize the \nGRBs based only on the INTEGRAL data, but the detection of afterglows \ncould confirm some of these events as genuine GRBs.\n\nSeveral bursts that were confirmed by off-line interactive analysis of the \nINTEGRAL data produced triggers above the threshold currently adopted for \nthe WEAK alerts. Recent examples include the two short bursts GRB 100703A \n(GCN Circ. n.10936) and GRB 110112B (GCN Circ. n.11562) and the long burst \nGRB 100909A (GCN Circ. n.11260).\n\nWEAK Alert Packets provide a single sky position, with error radius \nsmaller than 4 arcmin. They are intended for robotic telescopes which can \nreact without a negative impact on scheduled observing programmes. The \nvalue of SIGMA in the WEAK Alert Packet can be used as a figure of merit.\n\nWEAK Alert Packets may or may not be followed by the usual WAKEUP and/or \nREFINED Alert Packets, depending on the evolution of the detected signal.\nWEAK alerts for events belows WAKEUP threshold are neither confirmed nor\ncancelled with an OFFLINE packet.\n\nFor further details see\nhttp://ibas.iasf-milano.inaf.it/IBAS_News.html\n\nIt is recommended that current ibas clients upgrade their IBAS Client \nSoftware to the version 2.1.0 (available at \nhttp://www.isdc.unige.ch/integral/analysis#Software), although the \nprevious versions should process WEAK alert without problems."
}