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Determining the duration of the burst

The duration of the gamma-ray emission can be determined from any BAT light-curve using battblocks. Note there are 2 x t in the name, battblocks; think of this as being short for BAT-Time.

>battblocks durfile=dur.gti bkgsub=yes countscol=TOT_RATE
>Input data file
>Output GTI file name: bb.gti

         battblocks v1.17
     Input Data:
     Output GTI: bb.gti
 Events to Skip: 128     Changepoint log(prob) Prior: 6.000000
  Internal Tick: 1.000000e-04 s
  Lookback time: 0 s
 Bkg. Subtract?: yes (for fluence/T50/T90 calculations)
  Estimated T90 duration: 4.096 s +/- 0.128 s
  Estimated T50 duration: 2.432 s +/- 0.128 s
  Estimated Peak Interval: MET   281296750.52800000 +/- 0.500000 s
  Estimated background rate 1:     6806.667 near MET 281296728.800000 s
  Estimated background rate 2:     6090.188 near MET 281296901.504000 s
  Estimated total duration: 135.488 s (for data selection)
       (from MET 281296731.200000 to MET 281296866.688000)
  Estimated total fluence: 3459.961958 count
  Created GTI with 9 entries

In this example, the * light-curve has been used. This is the Swift onboard light-curve, which is telemetered to the ground via TDRSS. Thus, it will be located in the [obsid]/tdrss directory. See the BAT light-curve page for how to create your own light-curve, which can also be run through battblocks.

The GTI file has been called bb.gti because it is computed using Bayesian Blocks.

If txx=67.0 is included on the command line, the time boundaries defining 67% of the fluence are given (printed to the screen and in the dur.gti file) as well as T90 and T50.