BASIC TABLE

Bursts since the end of the 1B catalog (March 1992) occurred when the GRO tape recorders were experiencing numerous errors. Consequently, there are gaps in the data of many bursts that preclude valid measurement of peak flux, peak rate, fluence, or duration. Peak rates on the 1 second timescale from each detector are almost always available. These data (called MAXBC rates) can be used to determine burst location. Previous difficulties with this data type have been largely removed, and we now believe that the systematic errors for MAXBC-located bursts are the same as for bursts located with other data types. It is still true however, that the MAXBC-located bursts usually have larger statistical errors than would be the case if another data type were available. The comments table provides "L" comments for MAXBC-located bursts. A number of CGRO and BATSE flight software changes have significantly reduced the problem of data gaps since March of 1993.

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. Since then 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 file, with the overwrite flag is set to `Y'.

The BATSE trigger numbers correlate all the files for this catalog. The trigger number is a running sequence of BATSE triggers which include cosmic bursts, solar flares and other events. The sequence begins with trigger 105 and ends with trigger 3174.

Each burst has a unique catalog name. These BATSE catalog names later may be incorporated into a multi-spacecraft catalog with "GB" or "GRB" replacing this designation of "3B". The characters "3B " begin every BATSE catalog burst name, followed by the "yymmdd" of the burst. "yymmdd" is the two digit year, two digit month, and two digit day. When more than one gamma-ray burst occurs on one day, those bursts have a single letter suffix (B,C,D...), generally in order of intensity. Example: 3B 920503B refers to the second brightest burst that triggered BATSE May 3, 1992. The brightest burst on that day will have no suffix.

The burst trigger time is the end of the interval (64, 256 or 1024 ms) on which the burst triggered the detector.

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 chi^2 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 error in the table yields our estimate of the 68% confidence interval for the burst location error. The statistical error is believed to be Guassian. The systematic error distribution is not known very well, but may have a more extended tail than a Gaussian. The improvements in the 3B location algorithm are known to have significantly reduced this extended tail of the systematic error distribution.

There are twelve columns in this file:

1. The BATSE trigger number.
2. The BATSE Catalog burst name.
3. The truncated Julian Date (TJD) of the trigger TJD = JD - 2440000.5
4. The time in decimal seconds of day (UT) of the trigger.
5. right ascension (J2000) in decimal degrees.
6. declination (J2000) in decimal degrees.
7. Galactic longitude in decimal degrees.
8. Galactic latitude in decimal degrees.
9. radius in decimal degrees of positional error box.
10. angle in decimal degrees of geocenter (the angle between the burst and the nadir, as measured from the satellite).
11. overwrite flag: Y(true) if this burst overwrote an earlier, weaker trigger. N(false) otherwise.
12. overwritten flag: Y(true) if this burst was overwritten by a later, more intense trigger. N(false) otherwise.

   105 3B 910421    8367   33243.762     270.680      24.760      50.750      21.190       0.530     123.480  N  N
   107 3B 910423    8369   71684.719     193.470      -8.380     303.970      54.490      11.100     143.480  N  N
   108 3B 910424    8370   71006.570     201.310     -45.410     309.130      17.060      13.780      90.870  N  N
   109 3B 910425    8371    2265.710      91.290     -22.770     228.990     -19.940       1.020      88.580  N  N
   110 3B 910425B   8371   20253.289     335.940      25.770      85.830     -26.270       4.790      81.930  N  N
  ....
  3169 3B 940916    9611   63649.199     113.740      26.820     192.600      20.830       2.840     162.510  N  N
  3171 3B 940917    9612   62163.629      90.880       0.060     207.350     -10.620       3.000     122.550  N  N
  3173 3B 940918    9613   53474.801      65.530       3.220     190.610     -30.880       2.300     138.450  N  N
  3174 3B 940919    9614    2542.260     206.540      41.430      88.310      71.820       3.270     108.670  N  N

Web Curator: Nick Ruggiero, 301.286.1585, (Nick.Ruggiero@gsfc.nasa.gov). Last Modified: Friday, 11-Aug-95 17:07:45 EDT

Send general questions about CGRO to grohelp@athena.gsfc.nasa.gov

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