HETE2GCN - HETE-2 GCN Triggers Catalog

Overview

HETE-2 (the High Energy Transient Explorer) is an international mission designed to help unravel the mystery of Gamma-Ray Bursts (GRBs). The primary goal of HETE-2 is to determine the origin and nature of cosmic gamma-ray bursts (GRBs) by simultaneous observation of soft and medium X-rays and gamma-rays to provide precise localization of GRBs and identification of counterparts to these explosions. HETE-2 carries three science instruments: a set of wide-field gamma-ray spectrometers (FREGATE), a wide-field X-ray monitor (WXM, and a set of soft X-ray cameras (SXC) HETE-2 was launched on October 9, 2000, and declared fully operational on February 6, 2001.

Provenance

The contents of this HEASARC database table are based on online tables created by Scott Barthelmy and available at the http://gcn.gsfc.nasa.gov/ web site. The HEASARC table will be updated on a twice-per-week basis whenever the original tables are updated.

Description

The HETE2GCN database table summarizes HETE-2 triggers (real GRBs and X-ray transients) as distributed by the Gamma-ray Burst Coordinates Network (GCN; http://gcn.gsfc.nasa.gov/gcn_main.html).

For more information about HETE-2 please see the HETE-2 archive website: http://heasarc.gsfc.nasa.gov/docs/hete2/

Parameters

Trigger_Num
The GCN trigger number.

Time
The Universal Time (UT) of the start of the trigger.

Type
The type of burst notice. Each entry in the table can be one of these types:

  S/C_Alert - An S/C alert notifies that HETE has detected a burst,
      but does not guarantee that the trigger was due to a valid burst, or
      that a localization will be forthcoming. Strength of burst and
      timescale are supplied. This is the first Notice for a given trigger;
      it appears only once for each trigger. On rare occasions when the s/c
      is out of contact with the Secondary Ground Stations, the S/C will
      create the S/C_Alert before contact is re-established. This S/C_Alert
      will have the position determination and so it is possible to have an
      S/C_Alert with a position. This will happen <10% of the time.

  S/C_Update - These contain any new burst information and,
      most importantly, the best localizations to date from the WXM and/or
      SXC, along with "goodness" indicators for each. Zero to N messages of
      this type are possible (the 0 case is possible if the burst is over
      before a Secondary Ground Station comes into view and so only the
      S/C_Last would be transmitted -- this is rare). It is also possible to
      have these Updates without any position information. The operations
      team can (and has) commanded off the position content; this is
      happening while the s/c is looking at the very active Galactic Center
      which is producing a high rate of X-ray Burster triggers of very low
      detection significance (and therefore large position error).

  S/C_Last - These give a summary of the on-board analyses of the burst.
      This includes the timescale of the burst, peak brightness, best (if
      any) localizations by the WXM and SXC, and, if appropriate a "never
      mind" indicator and the reason for the burst's invalidation (ie a
      non-GRB trigger). This is the last of the real-time Notices; it appears
      only once for each trigger.

  GndAnalysis - contains the best positions available from ground
      post-processing at the time of the message. Multiple messages of this
      type are possible, if the ground team conducts even further analysis.
      Please note that it is possible for a trigger to be classified as
      "definite GBR" but contain no position. This happens when a burst does
      not have a large enough signal-to-noise ratio to calculate a reliable
      position, or when a burst is outside the FOV of the two imaging
      instruments and is determined to be a burst by looking at the FREGATE
      light curve or from some external information e.g information from
      another mission.

Instrument
The HETE-2 instrument which triggered. Tabulated values are WXM, SXC, TBD if not known yet as in an S/C_Alert Notice, "none" if the s/c decided there was enough to trigger, but not enough events to produce a position, or "neither" as in a GroundAnalysis Notice where it was determined that the trigger was a non-GRB.

RA
The Right Ascension of the burst, if known.

Dec
The Declination of the burst, if known.

LII
The Galactic Longitude of the burst, if known.

BII
The Galactic Latitude of the burst, if known.

Error_Radius
The error (in arcminutes, includes systematic + statistical uncertainties) in the specified position, if known.

Comments
Comment describing the observation results. If a column's information is not available or is not applicable, then that entry is listed as "n/a".

ID_Flag
A numerical value that can be used to identify the type of event that caused the trigger. These values are updated manually and are based on the GCN message stored in the `Comments' parameter.

The numerical values have the following meanings:

   GRB                       10
   Possible or Probable GRB   9
   SGR                        8
   GRB or XRB                 7
   Possible GRB or XRB        6
   XRB                        5
   Not a GRB                  4
   Invalid Trigger            3
   Particle Event             2
   Unclear                    1

ID_Verified
A flag used to indicate whether or not the `ID_Flag' has been verified by a human inspector. If the value is 'N', then the identification has been determined by a simple heuristic that looks for character string matches in the `Comments' parameter. In this case, the identification may be incorrect and some caution should be used. The value is 'Y' if the identification has been confirmed by a human inspector.

Contact Person

Questions regarding the HETE2GCN database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:28:41 EDT