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A Gamma‐Ray Burst Trigger Tool Kit

Year: 2002
Type: article
Abstract: The detection rate of a gamma-ray burst detector can be increased by using a count-rate trigger with many accumulation times Δ t and energy bands Δ E . Because a burst's peak flux varies when averaged over different Δ t and Δ E , the nominal sensitivity (the numerical value of the peak flux) of a trigger system is less important than how much fainter a burst could be at the detection threshold as Δ t and Δ E are changed. The relative sensitivity of different triggers can be quantified by referencing the detection threshold back to the peak flux for a fiducial value of Δ t and Δ E . This mapping between peak flux values for different sets of Δ t and Δ E varies from burst to burst. Quantitative estimates of the burst detection rate for a given detector and trigger system can be based on the observed rate at a measured peak flux value in this fiducial trigger. Predictions of a proposed trigger's burst detection rate depend on the assumed burst population, and these predictions can be wildly in error for triggers that differ significantly from previous missions. I base the fiducial rate on the BATSE observations: 550 bursts per sky above a peak flux of 0.3 photons cm -2 s -1 averaged over Δ t = 1.024 s and Δ E = 50-300 keV. Using a sample of 100 burst light curves, I find that triggering on all possible values of Δ t that are multiples of 0.064 s decreases the average threshold peak flux on the 1.024 s timescale by a factor of 0.6. Extending Δ E to lower energies includes the large flux of the X-ray background, increasing the background count rate. Consequently, a low-energy Δ E is advantageous only for very soft bursts. Whether a large fraction of the population of bright bursts is soft is disputed; the new population of X-ray flashes is soft but relatively faint.
DOI: 10.1086/342661
Language: English
Open Access status: bronze
OpenAlex ID: W2127700735
FWCI: 0.419
Cites: 10
Cited by: 33
Related to: 10