Catalog Notes
The catalog contains short naming for the time definition of the burst occurance and duration and for the localization region. These short naming definitions are provided in these notes together with
the main characteristics of the instruments that detected the bursts included in the catalog.
The instruments/missions included are only those mentioned in the original publication and it
is possible that the same burst have been detected by other instruments not listed here.
It is provided a list of observatories that have searched for and followed the afterglows
after the initail burst detection. A short description of all the GRBcat parameters is also provided here with the links to the online table help for more information on that parameter.
GRB Occurence Time
| Occurence Time |
Definition |
| Time at Instrument |
Often the time of a GRB event is reported as the trigger time in
the detecting instrument. Sometimes, especially for IPN or catalogs
that report simultaneous observations, the catalog reports the time for
one instrument involved in the burst detection, such as BATSE (on
CGRO) or WATCH (on GRANAT). |
| Earth Crossing Time |
The Earth crossing time is the time at which some feature, usually
the first large peak, would theoretically pass through Earth's center.
|
| Not Specified |
Many catalogs give a GRB time without specifying what time is measured. |
GRB Duration
| Duration Time |
Definition |
| T90 |
The 90% duration of the burst in seconds. T90 measures the
duration of the time interval during which 90% of the total
observed counts have been detected. The start of the T90
interval is defined by the time at which 5% of the total counts
have been detected, and the end of the T90 interval is
defined by the time at which 95% of the total counts have
been detected.
|
| T50 |
The 50% duration of the burst in seconds.
T50 measures the duration of the time interval during which
50% of the total observed counts have been detected.
The start of the T50 interval is defined by the time at which
25% of the total counts have been detected, and the end of the
T50 interval is defined by the time at which 75% of the total
counts have been detected
|
| T_other |
For some of the GRBs the duration is not provided as either
T50 or T90. The parameter "t_other" contains the duration, in
seconds, obtained using different methods: Castro-Tirado (1994)
reports the durations of two energy bands (6-15 keV and
15-100 keV), though the criterion for a time cut-off is not
given. Mitrofanov (1989a, b, c, 1990) reports the time during
which the counts in the 130-1450 keV range are greater or equal 3
sigma over the background. This parameter also records the
duration even when the method is not specified.
|
GRB Localization Region
| Geometry |
Definition |
| Circle |
The circle region is described by a center given in RA and Dec,
and a radius given in degrees.
|
| Annulus |
The annulus region is described by a center given in RA and Dec,
the radius of the annulus (corresponding to the center betewen
the inner and outer radii) and by the half-width of the annulus.
|
| Box |
The box region is defined by the corners of the box and a
center given in RA and Dec. The number of corners to describe
the box is up to six and for each corner the RA and Dec is
provided. In a few cases, Laros et al. (1998) report "hybrid"
boxes which are based on either the IPN and the BATSE-only or
COMPTEL-only error regions were used. These hybrid boxes are
defined by segments of one of the IPN annuli and an area.
|
| Dual |
The dual region type is for GRBs that had the localization
defined by two error circle regions. The dual regions are
defined by the centers of the two circle region
given in RA and Dec and their radii given in degrees.
|
| Intersection |
This localization region consists of a box derived from the
intersection of the IPN annulus with the region determined by a
different observatory. The table lists the corners of the
final box intersection and the parameters that defined the IPN
annulus (center, radius and half-width). The region of the
other observatories that intersect with the IPN annulus is
listed with the record for this GRB associated with the other
observatory.
|
| Annulus Intersection |
This localization region consists of in the intersection up to
three annuli. Each annulus is described by a center given in RA
and Dec, the radius of the annulus and by the half-width of the
annulus.
|
| Irregular |
The 'irregual' region are from the Kippen et al. (1998).
This localization region consist of a short thin arc segment
derived from a COMPTEL localization combined with an IPN
localization where the most likely position corresponds to the
maximum obtained from the integral distribution.
The COMPTEL localization consists of a circle error region
centered at the most likely position within that region.
|
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