SWIFT

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SWIFT
Medium-Class Explorer

• Catching Gamma-Ray Bursts on the Fly

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Overview

• GRB physics
• Current efforts in GRB research
• The SWIFT concept
• Instrument capabilities
• Summary - why SWIFT will deliver

Björn Flatt Sigrid de Jong Gijs Roelofs 27
August 2003
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GRB Physics

• What are the GRB progenitors?
• Long bursts supernovae?
• Short bursts ?
• What are the blast wave dynamics?

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GRB Physics

• What different GRB classes exist?
• Long/short bursts, other classes?
• Different physics?
• Can we use GRBs to probe the early universe?
• Young massive star origin?
• Look back further than ever before?
• Star formation rate at the very beginning?

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Current GRB Observations

• Only 1-2 events/month
• 40 manual afterglow measurements total
• X-ray follow-up 24h
• Optical follow-up 1h

Large selection effects
Were missing the blast wave!
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What You Need

• Sensitive ?-ray detector for deep survey
• Large sky coverage many events
• Quick, multi-waveband measurement of afterglow
  for blast wave reconstruction
• UV to probe GRB environment
• Direct broadcast of GRB location to ground

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The SWIFT Concept

• BAT
• GRB coordinates with 1-4 precision in 10s
• Satellite
• Slew to target autonomously in 20-70s
• XRT
• 5 X-ray imaging from 60s after burst
• UVOT
• 0.3 UV optical imaging from 60s after burst

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The Burst Alert Telescope (BAT)

• 15-150keV range
• 1.5sr field-of-view
• GRB position within 10s
• 5 times more sensitive than BATSE
• 150 events/yr 8-fold increase of current number
  in 2yr

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BAT Coded Aperture Mask

• ?-rays fall on lead tile pattern
• Produce shadow on the semiconductor detector
  array
• The shadow pattern is ray-traced back to
  determine direction of incidence

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The X-Ray Telescope (XRT)

• 0.2-10keV waveband
• 5 GRB position accuracy within 60s
• Lightcurves covering 7 orders of magnitude, with
  10ms time resolution
• X-ray spectra for redshift determination

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XRT Grazing Incidence Technique

• X-rays focused onto CCD using co-centric grazing
  incidence mirrors
• Spectroscopy using grazing incidence grating

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The UVOptical Telescope (UVOT)

• 170-650nm photometry in 6 colour bands up to
  mV24 in 1000s exposure
• Spectroscopy of bright afterglows (mVlt17) gives
  redshifts and extinction

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UVOT XMM-OM Design

• Using existing know-how and parts minimises cost
  and risk

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Summary

• SWIFT provides the deep, complete survey needed
  to further our understanding of GRBs
• All instruments based on low-risk, proven
  technology
• Re-using know-how and parts ensures MidEx budget
  conformity
• (Launch scheduled January 2004!)