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J/ApJ/563/80 3906 gamma-ray bursts BATSE triggers (Stern+, 2001)
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An off-line scan of the BATSE daily records and a large uniform sample
of gamma-ray bursts.
Stern B.E., Tikhomirova Y., Kompaneets D., Svensson R., Poutanen J.
<Astrophys. J. 563, 80 (2001)>
=2001ApJ...563...80S
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ADC_Keywords: Gamma rays
Mission_Name: CGRO
Keywords: astronomical data bases: miscellaneous - gamma rays: bursts -
methods: data analysis
Abstract:
During a scan of the archival BATSE daily records covering the entire
9.1yr (TJD 8369-11690) of the BATSE operation, 3906 gamma-ray bursts
(GRBs) have been detected. 2068 of these GRBs are previously known
BATSE triggers, while 1838 of them are new nontriggered bursts. It is
important that all events were detected in the same type of data and
were processed with the same procedure. Therefore these 3906 GRBs
constitute a uniform sample. We have created a publicly available
electronic data base
(http://www.astro.su.se/groups/head/grb_archive.html) containing this
sample. We describe the procedures of the data reduction, the
selection of the GRB candidates, and the statistical tests for
possible non-GRB contaminations. We also describe a novel test burst
method used to measure the scan efficiency and the information
obtained using the test bursts. Our scan decreases the BATSE detection
threshold to ~0.1photon/s/cm2. As a first result, we show that the
differential logN-logP distribution corrected for the detection
efficiency extends to low brightnesses without any indication of a
turnover. Any reasonable extrapolation of the new logN-logP to lower
brightnesses imply a rate of several thousands of GRBs in the universe
per year.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 53 3906 GRB characteristics
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See also:
IX/20 : The Fourth BATSE Burst Revised Catalog (Paciesas+ 1999)
J/ApJS/126/19 : BATSE gamma-ray burst spectral catalog. I. (Preece+, 2000)
J/ApJS/127/79 : BATSE occultation catalog of Gamma-Ray sources (Ling+, 2000)
J/ApJS/134/385 : Supplement to the BATSE catalogs (Kommers+, 2001)
http://www.astro.su.se/groups/head/grb_archive.html :
ftp archive of gamma ray bursts found in the continuous BATSE daily records
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- [STK2001] Event identifier (1)
8- 12 I5 s Start Start of the event within the day (2)
14- 17 I4 --- Trigger BATSE trigger number, or
1 for non-triggered events
19- 24 F6.3 ph/cm2/s Flux Peak flux in the 50-300keV range
26- 30 F5.1 deg RAdeg Right Ascension (J2000)
32- 36 F5.1 deg DEdeg Declination (J2000)
38- 41 F4.1 deg ErrPos Estimate for location error (3)
43- 45 I3 s T90 Duration rounded to integer seconds (4)
47- 49 I3 --- N50 Number of 1.024s bins where the signal
exceeds 50% of the peak value (4)
51 I1 --- K98 Identification with the K98 catalog (5)
53 I1 --- Gap Flag characterizing the data quality (6)
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Note (1): Event identifier consisting of TJD (origin 2440000.5)
plus an identifying letter
Note (2): The start time is defined as the beginning of the first 1.024s bin
within the burst window where the fitted background was exceeded by
4{sigma} in the 50-300keV range. If there was no 4{sigma} excess in
1.024s bins, the procedure is repeated with 2.048s, 4.096s, 8.192s
bins. If the burst consists of a few widely spaced episodes, the GRB
window covers the highest peak and does not necessarily coincide with
the actual beginning.
Note (3): Size of the 1{sigma} confidence area. Note that the 1{sigma} area
is usually not a circle - usually an ellipse, sometimes there are 2
minima, or a shapeless region. We present the MAXIMUM distance to the
1{sigma} boundary from the minimum. We have no estimates for
systematic errors, they differ from case to case, therefore we do not
recommend to rely on this estimates too much.
Note (4): The value of T90 for weak short events is strongly affected
by the Poisson noise and should be used with care.
Poisson fluctuations cause an overestimation of T90 for such events.
If N50 is 1, the peak flux is below 0.5photons/cm2/s and T90 is within
4s, then this is probably a one-bin event with T90<1s. Therefore we do
not recommend to use this duration distribution for a statistical
analysis for bursts of durations less than a few seconds.
Note (5): Flag equal to 1 means that the event exist in the K98 catalog
(Kommers et al., 2001, Cat. <J/ApJS/134/385>). The agreement in the
GRB location sometimes is very poor (difference up to 45{deg}). We
consider bursts to coincide if they overlap in time. If they differ
in time by 100-300s but have close locations, we considered them
identical anyway.
Note (6): Data quality flag:
0 = normal data;
1 = estimate of duration is problematic because of a data gap;
2 = estimate of the peak flux is problematic because of a data gap;
3 = 1 and 2 simultaneously.
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History:
From electronic version of the journal
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(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 18-Feb-2002