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The Burst Alert Telescope (BAT) on the SWIFT Midex Mission


he burst alert telescope (BAT) is one of three instruments on the Swift MIDEX spacecraft to study gamma-ray bursts (GRBs). The BAT first detects the GRB and localizes the burst direction to an accuracy of 1–4 arcmin within 20 s after the start of the event. The GRB trigger initiates an autonomous spacecraft slew to point the two narrow field-of-view (FOV) instruments at the burst location within 20–70 s so to make follow-up X-ray and optical observations. The BAT is a wide-FOV, coded-aperture instrument with a CdZnTe detector plane. The detector plane is composed of 32,768 pieces of CdZnTe (4×4×2 mm), and the coded-aperture mask is composed of ∼52,000 pieces of lead (5×5×1 mm) with a 1-m separation between mask and detector plane. The BAT operates over the 15–150 keV energy range with ∼7 keV resolution, a sensitivity of ∼10−8 erg s−1 cm−2, and a 1.4 sr (half-coded) FOV. We expect to detect > 100 GRBs/year for a 2-year mission. The BAT also performs an all-sky hard X-ray survey with a sensitivity of ∼2 m Crab (systematic limit) and it serves as a hard X-ray transient monitor.

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Correspondence to Scott D. Barthelmy.

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Barthelmy, S.D., Barbier, L.M., Cummings, J.R. et al. The Burst Alert Telescope (BAT) on the SWIFT Midex Mission. Space Sci Rev 120, 143–164 (2005).

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  • gamma-ray
  • GRB
  • hard X-ray
  • survey
  • burst
  • afterglow
  • CZT
  • coded aperture
  • astrophysics
  • cosmology