FERMIGBRST - Fermi GBM Burst Catalog

Overview

The GBM consists of an array of 12 sodium iodide (NaI) detectors which cover the lower end of the energy range up to 1 MeV. The GBM triggers off of the rates in the NaI detectors. These detectors are placed around the Fermi spacecraft with different orientations to provide the required sensitivity and FOV. The cosine-like angular response of the thin NaI detectors is used to localize burst sources by comparing rates from detectors with different viewing angles. To cover higher energies, the GBM also includes two bismuth germanate (BGO) detectors.

The signals from all 14 GBM detectors are collected by a central Data Processing Unit (DPU). This unit digitizes and time-tags the detectors pulse height signals, packages the resulting data into several different types for transmission to the ground (via the Fermi spacecraft), and performs various data processing tasks such as autonomous burst triggering.

Bulletin

Caveats

References

Provenance

Parameters

Version
This parameter specifies the current version of the catalog entry file. New versions are provided by the GIOC as additional data are added or further analysis done. Thus the early versions might have only basic burst quantities such as duration in the header, while later versions will have spectra in extensions (which are not provided in earlier versions).

Trigger_Name
This parameter contains the Fermi trigger designation that is assigned for each new trigger detected. The naming scheme used is bnyymmddfff, where yymmdd is the date of the burst (yy, the year minus 2000; mm, the two-digit month; and dd, the two-digit day of the month) and fff = fraction of day.

Name
The designation of the source of the trigger. The name will initially be GRByymmddfff, where yymmdd is the 2-digit year, month and day of the burst and fff the fraction of the day, as assigned by pipeline processing. The name will eventually be changed to the GRByymmddx format, where x is null or 'A' or 'B' etc. Re-naming to this format requires human intervention, noting whether another burst was detected on the same day.

RA
The Right Ascension of the trigger in the selected equinox. This was given in J2000 decimal degree coordinates in the original table.

Dec
The Declination of the X-ray source in the selected equinox. This was given in J2000 decimal degree coordinates in the original table.

LII
The Galactic Longitude of the trigger, derived from the trigger RA and Dec.

BII
The Galactic Latitude of the trigger, derived from the trigger RA and Dec.

Error_Radius
This parameter is the uncertainty in the position, in degrees.

Time
The start time of the observation, originally provided in Fermi Mission Elapsed Time (MET) format and converted to UTC.

End_Time
The end time of the observation, originally provided in Fermi Mission Elapsed Time (MET) format and converted to UTC.

Trigger_Time
The time at which the trigger occurred, originally provided in Fermi Mission Elapsed Time (MET) format and converted to UTC.

Trigger_Type
The classification of the trigger. The following trigger types are given in the Fermi File Format Document for this file (GS-105):

             ERROR        Error
             UNRELOC      Unreliable location
             LOCLPAR      Local particles
             BELOWHZ      Source below the horizon
             GRB          Gamma-ray burst
             SGR          Generic soft gamma repeater
             TRANSNT      Generic transient
             DISTPAR      Distance particle event
             SFL          Solar flare
             CYGX1        Variation of Cyg X-1
             SGR1806      Burst from SGR1806+20
             GROJ422      Variation of GRO J0422+32
             TGF          Terrestrial Gamma-Ray Flash
  

Reliability
Probability assigned to the classification of the trigger by the GBM flight software, expressed as a percentage (with 100% being most probable).

Trigger_Timescale
The timescale (in milliseconds) that actually produced the trigger. GBM has many, from 16 ms up to about 4 s.

Trigger_Algorithm
This parameter contains the trigger algorithm number used by the GBM flight software. Currently, there is only one algorithm used which is assigned the number 1. Future versions of the flight software may use other algorthims.

Channel_Low
The lowest energy channel in which the trigger was detected.

Channel_High
The highest energy channel in which the trigger was detected.

ADC_Low
The lowest energy channel, after analog-digital conversion, in which the trigger was detected. Channel values after analog-digital conversion are in the range 0 - 4095.

ADC_High
The highest energy channel, after analog-digital conversion, in which the trigger was detected. Channel values after analog-digital conversion are in the range 0 - 4095.

Detector_Mask
This field contains a series of flags which indicate which NaI detectors (0-11) were triggered. The value 1 at a particular position indicates that that detector was triggered. Similarly, the value 0 indicates that that dectector was not triggered.

Geo_Long
The spacecraft's geographical north latitude, in degrees.

Geo_Lat
The spacecraft's geographical east longitude, in degrees.

RA_Scx
The Right Ascension of the pointing of the spacecraft's X-axis, in J2000 degrees.

Dec_Scx
The Declination of the pointing of the spacecraft's X-axis, in J2000 degrees.

RA_Scz
The Right Ascension of the pointing of the spacecraft's Z-axis, in J2000 degrees.

Dec_Scz
The Declination of the pointing of the spacecraft's Z-axis, in J2000 degrees.

Fluence_25_1000
The fluence (the flux integrated over the time of the burst) in the 25-1000 keV band, in erg/cm².

Fluence_25_1000_Error
The 1-sigma statistical uncertainty of the fluence in the 25-1000 keV band, in erg/cm².

Peakflux_25_1000
The peak flux in the 25-1000 keV band, in erg/cm².

Peakflux_25_1000_Error
The 1-sigma statistical uncertainty of the 25-1000 keV peak flux, in erg/cm².

Peakflux_Interval
The time interval for the peak flux in seconds after the start of the burst.

Peakflux_50_300
The peak flux in the 50-300 keV band, in erg/cm².

Peakflux_50_300_Error
The 1-sigma statistical uncertainty of the 50-300 keV peak flux, in erg/cm².

T90
The 90% burst duration, 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 1-sigma statistical uncertainty in the T90 duration.

T90_Start
The start of T90 interval (in Mission Elapsed Time seconds).

T50
The 50% burst duration, in seconds. T50 is defined using the times at which 25% and 75% of the counts have been detected.

T50_Error
The 1-sigma statistical uncertainty in the T50 duration.

T50_Start
The start of T50 interval (in Mission Elapsed Time seconds).

Back_Interval_Low
The duration for the lower background selection interval (in Mission Elapsed Time seconds).

Back_Interval_High
The duration for upper background selection interval (in Mission Elapsed Time seconds).

Spectrum_Flag
This flag parameter contains a value, either 'Y' or 'N', which indicates that a DETECTOR DATA extension exists in the burst catalog entry file. This extension provides deconvolved spectra over the burst.

Fit_Flag
This flag parameter contains a value, either 'Y' or 'N', which indicates that a FIT PARAMETERS extension exists in the burst catalog entry file. This extension provides the spectral parameters resulting from fitting spectra over the burst.

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