Galactic Astronomy - Paper

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Galactic Astronomy- Paper

• Luminosity Functions of GRB Afterglows

Dong-hyun Lee 2007/09/18
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LF of GRB Afterglow summary

• Using standard fireball model gt create virtual
  population of GRB afterglow gt study LFs
• Numerical sim. Varying parameters of fireball
  model randomly gt create virtual population gt
  compare 1day observational data gt check the
  consistency of model
• LFs are described by a func. sim. to log normal
  dist. with exponential cutoff func. parameters
  are dep. on model parameters gt comparison
  difficult to explain simultaneously X-ray
  optical data
• Standard fireball model is OK?
• We need some emission mechanism.

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Intro.

• Standard fireball model since 1997
• Used to explain GRB afterglow
• Observed data from Swift satellite(rapid burst)
  its XRT(detected afterglow 200)
• LFs can be described to a high accuracy by anal.
  func.

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Virtual population of afterglow

• Numerical calculation Johannessen et al.(2006)
• Based on standard fireball jet model E is
  injected instaneously into a narrow jet
• Model parameter varying logarithmic (except p)
• Fix z1 (to concentrate on intrinsic properties)

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Luminosity functions

• Fig1 typical LFs at 3 diff. freq.
• L0 characteristic lum. Sigma lambda
  affect width of func. controling shape
  sigma stronger effect
• 4 tests (to cover all basic effects)
• Changed upper limit keeping lower limit fixed
• Changed lower limit keeping upper limit fixed
• Width changed with a fixed center
• Center changed with a fixed width

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Luminosity functions
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Luminosity functions
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Comparison with Observations

• Data normalized to an observers time of 1 day
  z1
• Difference b/w optical
• X-ray lum. func.
• bimodality
• Model needs to be
• refined
• Observed optical LF
• may be incomplete

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Discussion Conclusions

• LF simple log normal dist. with exponential
  cutoff
• Shape of LF is not sensitive to shape of model
  parameter dist.
• Sigma lambda are somewhat dep. on model
  parameter dist. gt but not significant
  correlations
• Generally, good agreement with observations
• Incompatibility b/w optical X-ray bimodality
  in optical but not in X-ray
• More detailed model or entirely different one is
  required