BATSEGRB - CGRO/BATSE Gamma-Ray Burst Catalog

Overview

This database table comprises the gamma-ray bursts detected by the BATSE instrument on the Compton Gamma-Ray Observatory (CGRO). It includes the gamma-ray bursts from the BATSE 4B Catalog (triggers 105 through 5586, observed between April 19, 1991, and August 29, 1996) as well as a large number of triggered bursts since the publication of the BATSE 4B Catalog.

All BATSE trigger data from the CGRO mission are available through this facility. As part of a final archiving effort, the BATSE instrument team is making minor refinements to certain data products. These revised products will be delivered to the HEASARC as soon as they are produced and tested. Certain burst catalog parameters, notably the position information, may be revised through improved analyses and instrumental calibration. The final catalog will be posted here as soon as it is completed.

References

The BATSE Current Gamma-Ray Burst Catalog, the BATSE GRB Team,
http://gammaray.msfc.nasa.gov/batse/grb/catalog/current/

The Fourth BATSE Gamma-Ray Burst Catalog, C. A. Meegan et al.,
in "Gamma-Ray Bursts: the Fourth Huntsville Symposium (IAP No. 428)",
ed. Meegan, C.A., Preece, R.D. and Koshut, T.M., p. 1. (1997).

The Third BATSE BATSE Gamma-Ray Burst Catalog, C. A. Meegan et al.,
ApJS, 106, 65. (1996).

Provenance

The data files used to construct this database table are obtained from the following pages on the BATSE GRB Team website:

BATSE Current Gamma-Ray Burst Catalog:
    http://gammaray.msfc.nasa.gov/batse/grb/catalog/current/

Some flux and fluence data and all the comments are from the BATSE 4B Catalog:
    http://gammaray.msfc.nasa.gov/batse/grb/catalog/4b/

This database table was first created at the HEASARC in June 2001. The HEASARC version is automatically updated within one week of whenever the data files located at http://gammaray.msfc.nasa.gov/batse/grb/catalog/current/ are changed.

Data Products

The following is a summary of the most useful BATSE data files and their contents:

Naming Convention         Contents

tte_bfits_YYYY.fits       time-sequenced 4-energy channel data bracketing
                          trigger; combines discla, preb, discsc, and tte.

discsc_bfits_YYYY.fits    time-sequenced 4-energy channel data bracketing
                          time of burst trigger for triggered detectors;
                          combines data types discla, preb and discsc.

(s)her_bfits_X_YYYY.fits  time-sequenced 128 energy channel data bracketing
                          time of burst trigger for specified detector;
                          combines datatypes her and herb - suggested data
                          type for 128 energy channel burst analysis.

mer_bfits_YYYY.fits       time-sequenced 16-energy channel data for times
                          bracketing burst trigger - triggered detectors
                          only; combines mer and cont datatypes - suggested
                          for 16-energy channel burst analysis.

discsc_drm_YYYY.fits      detector response matrix for 4 energy channel burst
                          data triggered detectors only; used with 4-energy
                          channel data to determine burst photon spectra.

her_drm_X_YYYY.fits       detector response matrix for 128-energy channel
                          burst data for specified detector; used with
                          128-energy channel counts data to generate burst
                          photon spectra.

mer_drm_YYYY.fits         detector response matrix for 16-energy channel burst
                          data triggered detectors only; used with 16-energy
                          channel data to generate burst photon spectra.

cont_TJD_fits             8 BATSE detectors, 2.048s resolution/16 energy
                          channels.

discla_TJD.fits           8 BATSE detectors, 1.024 s resolution/4 energy
                          channels.

XXX_TJD1_TJD2_his.fits    Occultation histories.

XXX_TJD1_TJD2_nhis.fits   Data for one or more BATSE detectors for available
                          energy channels as source count rate (counts/sec)
                          from which the background has been subtracted -
                          used for light curves.

XXX_TJD_lad_p11.fits      Pulsar low level data.

XXX_TJD1_TJD2_lad_olc     Light curve file for a given pulsar.

where YYYY = trigger number, XXXX = source name, TJD = Truncated Julian Day, X = detector number.

Notice that, because of the instrument configuration at the time of the event, the same files are not available for all triggers. Spectral (SD) data are prefixed with an 's' (e.g. 'sher').

Available data taken prior to the trigger may contain the beginning of the triggering event before it satisfied the triggering criteria. Background-type files can be used to remove background signal levels from the triggered period. The BFITS data files - containing burst and background spectral data as a function of time - and the detector response matrices (DRM) - modeling the instrument response to account for scattering and other effects - are extremely useful for gamma-ray burst analysis. Also, the BFITS and DRM files can be converted to PHA-II and RMF format for analysis with XSPEC using available FTOOLS. Other file types exist, notice, and advice on their use is obtainable at grohelp@athena.gsfc.nasa.gov.

Burst Durations

This database table contains values for T90 and T50, quantities related to burst duration, for 1234 gamma-ray bursts that triggered the BATSE LAD detectors between April 1991 and 29 August 1996. 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 is similarly defined using the times at which 25% and 75% of the counts have been detected. T90 and T50 are calculated using data summed over the 4 LAD discriminator channels and using data summed over only those detectors that satisfied the BATSE trigger criteria.

Users must note that T90 and T50 are not available for those bursts which suffer from data gaps during the event; the integration procedure inherently fails in these cases. However, visual estimates of the burst duration are provided in the parameter Comments_Duration for those bursts with sufficient data coverage. Users may also find other pertinent comments concerning the calculated value of T90 and T50 therein, and it is highly recommended that this parameter be consulted before any distribution selected on T90 or T50 is used.

Count Rates

This database table contains triggered bursts observed from shortly after the launch of CGRO in April 1991 until the end of scientific operations in May 2000. For many of these triggered bursts peak count rates in units of the threshold count rate, and threshold count rates, are available. Some bursts do not have this since insufficient data exist to determine either their peak counts or their threshold.

The BATSE on-board software tests for bursts by comparing the count rates on the eight large-area detectors to threshold levels for three separate time intervals: 64 ms, 256 ms, and 1024 ms. A burst trigger occurs if the count rate is above threshold in two or more detectors simultaneously. The thresholds are set by command to a specified number of standard deviations above background (nominally 5.5 sigma). Background rates are recomputed every 17 seconds. The thresholds exhibit a coarse quantization that results from truncating the square root of the 64-ms count rate. Since we require that rates be above the thresholds of at least two detectors, the trigger threshold is determined by the threshold of the second most brightly illuminated detector. When a burst trigger occurs, subsequent triggers are disabled during the accumulation period when the BATSE burst memories accumulate data. These data are then transmitted. During this readout period, the 64-ms threshold is revised to correspond to the maximum rate attained by the current burst, and triggering is disabled on the 256-ms and 1024-ms timescales. Bursts intense enough to trigger during this readout period are termed "over- writes". They are recognized in the database by the value of -999 in the threshold values for 256-ms and 1024-ms (called threshold_256 and threshold_1024 in this database).

Since a trigger can occur on any of the three timescales, there are often cases in which the maximum rate will be below threshold on one or two of the timescales. The value of V/Vmax can be determined for any burst by selecting the maximum of the three peak rates, raised to the -3/2 power. Many bursts have unknown counts or thresholds on one or more timescales. These are marked by a "-999" in the database. This can happen for one of the follow- ing reasons: (1) If the trigger occurs on the 64-ms timescale during the peak 256 ms rate, then the peak 256-ms rate is not found; (2) If the 64-ms peak rate never exceeds the 64-ms threshold, and it occurs before the trigger time, then the peak 64-ms rate is not found; (3) If the 256-ms peak rate never exceeds the 256-ms threshold, and it occurs before the trigger time, then the peak 256-ms rate is not found. Note that items 2 and 3 do not affect V/Vmax, since these peak rates do not exceed threshold; item 1 can, on rare occasions, lead to an overestimate of V/Vmax.

Triggers

The on-board software determines when a trigger occurs. When a burst trigger occurs, subsequent triggers are disabled for an accumulation period, during which the BATSE burst memories accumulate data. The accumulation period was 242 seconds until Dec 17, 1992, and from Jan 8, 1996 to Feb 25, 1997. At all other times it has been 573 seconds. The stored burst data are then transmitted; the readout time for all triggers was 90 minutes until Dec 17, 1992. At that date, the flight software was revised to suspend readouts during telemetry gaps and to truncate readouts of weak events. This resulted in a variable readout time. During the burst data readout, the 64-ms threshold is revised to correspond to the maximum rate attained by the current burst, and triggering is disabled on the 256-ms and 1024-ms timescales. Bursts intense enough to trigger over this revised 64-ms value are termed "overwrites". They appear as triggers in this catalog, with the overwrite flag is set to 'Y'.

In analyzing these data, it is important to note that the trigger criteria, including the energy range, have been changed quite often since the end of the 3B catalog. This information is contained in the Trigger Criteria Table available at http://gammaray.msfc.nasa.gov/batse/grb/catalog/4b/4br_trigger_criteria.html

Fluxes and Fluences

This database table contains the fluence and peak flux values for the BATSE gamma-ray bursts since 19 April, 1991. All fluences and their errors have units of of ergs/cm². All peak fluxes and their errors have units of photons/cm²/sec. The errors are the one-sigma statistical errors. The peak flux times are expressed in decimal seconds relative to the burst trigger time for the end of the interval in which the flux was calculated. The channel 1,2,3 and 4 fluences cover the energy ranges 20-50 keV, 50-100 keV, 100-300 keV, and E > 300 keV, respectively. The peak flux energy range is 50-300 keV, coinciding with the energy range of the nominal BATSE on-board burst trigger. Since channel 4 is an integral channel, fluences given for this channel are quite sensitive to the assumed spectral form. Spectral analyses in this energy range should be performed with higher resolution data types. Many of the bursts between March 1992 and March 1993 have significant gaps in the data and therefore do not have tabulated fluxes and fluences.

Parameters

Trigger_Num
The BATSE trigger number. This is a running sequence number of BATSE triggers which include cosmic bursts, solar flares and other events. It is the primary means of identification for events in this catalog.

Name
The BATSE burst name. Each burst has a unique catalog name. These names may have a prefix of either "4B" or "GRB". The "4B" prefix means that the burst is listed in BATSE 4B Catalog, while the "GRB" prefix means that the burst is listed in the BATSE Current Gamma-Ray Burst Catalog. The prefix is followed by the "yymmdd" (date) of the burst, where "yymmdd" is the two digit year, two digit month, and two digit day. An ending hyphen is added when this name is not unique, i.e., when there were two or more bursts on a particular day.

RA
The Right Ascension of the object that triggered the BATSE instrument.

Dec
The Declination of the object that triggered the BATSE instrument.

LII
Galactic longitude of the object that triggered the BATSE instrument.

BII
Galactic latitude of the object that triggered the BATSE instrument.

Day_Trigger
The truncated Julian Date (TJD) of the trigger: TJD = JD - 2440000.5.

Time
The burst trigger time. This parameter has been added by the HEASARC for the convenience of temporal searches and cross-correlations. The burst trigger time is the end of the interval (64, 256 or 1024 ms) in which the burst triggered the detector. The time system for the values is UT.

Seconds_Trigger
The burst trigger time, in decimal seconds of the day (UT) on which it occurred. The burst trigger time is the end of the interval (64, 256 or 1024 ms) in which the burst triggered the detector.

Error_Radius
The radius in decimal degrees of the positional error box. The error in angular location is the radius of a circle having the same area as the 68% confidence ellipse defined by the formal covariance matrix from a chi² fit on the assumption of normal errors. The error is based solely on the Poisson uncertainty in the BATSE measurement of burst flux by each Large Area Detector. There is, in addition, an RMS systematic error of approximately 1.6 degrees. Adding 1.6 degrees in quadrature to the value of this parameter yields the BATSE team's estimate of the 68% confidence interval for the burst location error. The statistical error is believed to be Gaussian. The systematic error distribution has a more extended tail than a Gaussian.

Earth_Angle
The angle in decimal degrees of the geocenter, i.e., the angle between the burst and the nadir, as measured from the satellite.

Overwrite
The overwrite flag: this is Y (true) if this burst overwrote an earlier, weaker trigger, N (false) otherwise.

Overwritten
The overwritten flag: this is Y (true) if this burst was overwritten by a later, more intense trigger, N (false) otherwise.

Max_Cts_64
The maximum counts in the second most brightly illuminated detector divided by the threshold count rate on the 64-ms timescale.

Threshold_64
The trigger threshold on the 64-ms timescale. It is the number of counts in 64 ms required to trigger the second most brightly illuminated detector for this particular burst.

Flux_64
The peak flux on the 64-ms timescale in units of photons/cm²/sec.

Flux_64_Error
The one-sigma statistical error in the peak flux on the 64-ms timescale.

Flux_64_Time
The time of the peak flux on the 64-ms timescale, in decimal seconds relative to the burst trigger time for the end of the interval in which the flux was calculated.

Max_Cts_256
The maximum counts in the second most brightly illuminated detector divided by the threshold count rate on the 256-ms timescale.

Threshold_256
The trigger threshold on the 256-ms timescale. It is the number of counts in 256 ms required to trigger the second most brightly illuminated detector for this particular burst.

Flux_256
The peak flux on the 256-ms timescale in units of photons/cm²/sec.

Flux_256_Error
The one-sigma statistical error in the peak flux on the 256-ms timescale.

Flux_256_Time
The time of the peak flux on the 256-ms timescale, in decimal seconds relative to the burst trigger time for the end of the interval in which the flux was calculated.

Max_Cts_1024
The maximum counts in the second most brightly illuminated detector divided by the threshold count rate on the 1024-ms timescale.

Threshold_1024
The trigger threshold on the 1024-ms timescale. It is the number of counts in 1024 ms required to trigger the second most brightly illuminated detector for this particular burst.

Flux_1024
The peak flux on the 1024-ms timescale in units of photons/cm²/sec.

Flux_1024_Error
The one-sigma statistical error in the peak flux on the 1024-ms timescale.

Flux_1024_Time
The time of the peak flux on the 1024-ms timescale, in decimal seconds relative to the burst trigger time for the end of the interval in which the flux was calculated.

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.

T50_Error
The uncertainly in the T50 duration.

T50_Start
The start time of the T50 interval, relative to the trigger time (Time), in seconds.

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.

T90_Error
The uncertainty in the T90 duration.

T90_Start
The start time of the T90 interval, relative to the trigger time (Time), in seconds.

Fluence_1
The fluence for Channel 1 (energy range 20-50 keV), in units of ergs/cm².

Fluence_1_Error
The error in the fluence for Channel 1.

Fluence_2
The fluence for Channel 2 (energy range 50-100 keV), in units of ergs/cm².

Fluence_2_Error
The error in the fluence for Channel 2.

Fluence_3
The fluence for Channel 3 (energy range 100-300 keV), in units of ergs/cm².

Fluence_3_Error
The error in the fluence for Channel 3.

Fluence_4
The fluence for Channel 4 (energy range E > 300 keV), in units of ergs/cm². Since channel 4 is an integral channel, fluences given for this channel are quite sensitive to the assumed spectral form. Spectral analyses in this energy range should be performed with higher resolution data types.

Fluence_4_Error
The error in the fluence for Channel 4.

Comments_Quality
Comments on data quality for: not all gamma-ray bursts have such comments.

Comments_Otherobs
Comments on additional observations by other instruments: not all gamma-ray bursts have such comments.

Comments_General
General comments: not all gamma-ray bursts have such comments.

Comments_Position
Comments on the gamma-ray burst coordinates: not all gamma-ray bursts have such comments.

Comments_Duration
Comments on the gamma-ray burst duration: not all gamma-ray bursts have such comments.

Contact Person

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

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:24:58 EDT