{
  "bibcode": "2002GCN..1539....1H",
  "body": "IPN GCN Circulars now to be issued without restriction\n______________________________________________________\n\n\nUp to now, the IPN collaboration has been filtering its GCN Circulars\nand Notices on GRBs to include only localizations which satisfy three\ncriteria:\n\n1. Relatively small error boxes (<~ 1000 arcmin2) \n2. Relatively rapidly determined error boxes (<~100 hours) \n3. Error boxes with relatively small maximum dimension in any direction (<~30 arcmin)\n\nThese filters were tailored to the requirements of astronomers\nsearching for long-wavelength GRB afterglows. The resulting GCN rate\nhas been roughly one per week over the past several years, with large\nfluctuations in this rate due to solar activity and the start-up and\nshutdown of various missions.\n\nHowever, following discussions with members of the community, we\nbelieve that, in order to better serve the needs of astronomers\nsearching for other GRB-related phenomena, including neutrinos,\ngravitational radiation, and VHE gamma-rays, it is worthwhile to remove\nall filters from IPN GRBs. Accordingly, we will proceed to issue GCN\nCirculars which give information on bursts localized to annuli,\nsections of annuli, double error boxes, and so on, regardless of the\narea, maximum dimension, or delay in obtaining the error box.  These\nCirculars will be issued as soon as possible after receipt of the\ndata.  The removal of filters should at least double the GCN message\nrate; the majority of these Circulars will be issued within several\ndays of a burst, although outliers will always be present.  (We do not\nplan to issue this information as GCN Notices, unless the circumstances\nare exceptional, or a clear desire to have such Notices is expressed by\nmembers of the community.)  As always, all such information should be\nunderstood to be preliminary and subject to refinement when final data\n(such as spacecraft ephemeris and timing) become available, which\ntakes up to about one month, depending on the spacecraft.   Apart from\nexceptional cases, we will not issue final localizations as GCN\nCirculars, but instead defer them to publications in the refereed\nliterature.\n\nWe will use several techniques in addition to arrival-time analysis to\nconstrain GRB arrival directions as much as possible.  They include\nEarth-blocking, Mars-blocking, and ecliptic latitude determination.  A\nbrief discussion of some of these techniques may be found at\nssl.berkeley.edu/ipn3/statusreport.htm.\n\nUnconfirmed events (i.e., events observed by a single detector, or by\nseveral detectors on a single spacecraft) pose a particular problem.\nIn many cases, such events can safely be assumed to be cosmic due to\ntheir energy spectra and time histories.  However, some cases are\nharder to judge.  We will treat unconfirmed events in such a way as to\nminimize the false positive rate, while maximizing the completeness of\nthe sample.  Roughly speaking, we expect the overall result to be a GRB\nsample that is over 90% complete, with an over 90% probability that any\nunconfirmed event is indeed cosmic.  (Note that some unconfirmed events\nmay be localized, and some confirmed events may be unlocalized, due to\nthe nature of the IPN and its experiments.)\n\nWe will attempt to specify the nature of the event and its localization\nin the subject line of the circular, as far as possible.\n\nQuestions about specific events, or questions such as \"did any\nspacecraft observe a burst on day X at time Y?\", can be addressed to\nkhurley@sunspot.ssl.berkeley.edu.",
  "circularId": 1539,
  "createdOn": 1031680083000,
  "email": "khurley@sunspot.ssl.berkeley.edu",
  "subject": "IPN GCN Circulars now to be issued without restriction",
  "submitter": "Kevin Hurley at UCBerkeley/SSL  <khurley@sunspot.ssl.berkeley.edu>"
}