Short Gamma Ray Bursts Unraveled

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Short Gamma Ray Bursts Unraveled

• Stan Whitcomb
• Journal Talk 6 October 2005

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Short Gamma Ray Bursts

• 1961 Vela spy satellite launched to observe
  gamma rays that might be emitted by underground
  nuclear testing in the former Soviet Union
• Quickly recognizedas astrophysical
• Divided into twoclasses by lengthand spectrum

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Clearly Two Populations

• Short bursts 0.010 2 seconds
• Very little structure
• Long bursts 3-200 seconds
• Substantial Structure

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Isotropy Indicates at Great Distance
Credit NASA, Compton Gamma Ray Observatory
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First SWIFT LocationGRB050509b (May 9, 2005)
Burst Alert Telescope (BAT)
X Ray Telescope (XRT)
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GRB050509b

• Total duration 40 ms (clearly in the short GRB
  class)
• Weak signal gave poor location(10 error circle)
• Near edge of large elliptical galaxy (z 0.225)
• Apparent distance from center35 kpc
• Some possibility that couldbe from background
  galaxy

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GRB050709
70-220 ms spike
Long, soft afterglow?
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Hubble images of GRB050709 Afterglow
5 days
35 days
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GRB050709

• Associated with blue dwarf galaxy, lots of star
  formation
• z 0.16, luminosity distance 747 Mpc
• Distance to galactic center 3 kpc, not in the
  region of highest star formation
• Afterglow due to expansion of relativistic plasma
  (G 100, v 0.9999c) into interstellar medium,
  or something more complex?
• Beaming fraction 0.03

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GRB050724

• Unambiguous association with elliptical galaxy(z
  0.258) because of optical afterglow and high
  resolution Chandra position
• At the longer end of short GRBs (3 s total with
  0.25s spike)
• Distance from galactic center 4 kpc
• Beaming fraction 0.01

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GRB050724 a NS-BH merger?
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GRB050813

• Manuscript in preparation
• Hints that it might also be in an elliptical
  galaxy(z0.722)
• ???