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Characteristics of Swift ’s intermediate population bursts

Characteristics of Swift ’s intermediate population bursts.

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Characteristics of Swift ’s intermediate population bursts

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  1. Characteristics of Swift’s intermediate population bursts A. de Ugarte Postigo, I. Horvath , P. Veres , Z. Bagoly , L. G. Balazs , D. A. Kann , C. C. Thöne , P. D’Avanzo, M.A. Aloy , S. Campana , S. Foley , J. Mao , S. Covino, A. J. Castro-Tirado, J. P. U. Fynbo , J. Gorosabel , P. Jakobsson , L. Amati , and M. Nardini

  2. Sample and classification • Classification by Horváth et al. (2010). Clustering analysis. • First 4 years of Swift. • Burst with redshift (136): • 12 short • 28 intermediate • 82 long • Contamination is significant!

  3. Redshift distribution • Median redshift: • 0.46 for short • 1.33 for intermediate • 2.05 for long • K-S test: • Short-long: 0.0004% • Short-interm.: 0.6% • Interm.-long: 7%

  4. Afterglow luminosity: X-ray • K-S test at 100 sec: • Short-Interm.: 2.2% • Short-Long: 0.02% • Interm.-Long: 0.003% • K-S test at 104 sec: • Short-Interm.: 0.13% • Short-Long: 0.003% • Interm.-Long: 0.002%

  5. Afterglow luminosity: Optical • K-S test at 100 sec: • Interm.-Long: 11% • K-S test at 104 sec: • Interm.-Long: 3.3%

  6. Dark bursts • Intermediate: 5 out of 32 are dark (16%). • Long: 27 out of 90 are dark (30%). • K-S test with only detections give 4.6% of coming from the same population.

  7. Hydrogen column density • X-ray: Intermediate bursts similar to long: • K-S test gives 5.1% • Optical: Small amount of data to do statistics. There is no clear trend.

  8. Optical extinction • Same distribution as for long bursts. • K-S test gives 61% probability of coming from the same population.

  9. Epeak vs. Eiso correlation • Valid for long GRBs but not for short • Mostly valid for intermediate bursts. • Slight trend to find them above the fit

  10. Spectral lags • Short have negligible lags, while intermediate and long tend to positive lags. • K-S test: • Short-Long: 0.017% • Short-Interm.: 0.009% • Interm.-Long: 77%

  11. Conclusions • Intermediate GRBs are similar to long GRBs in: • Spectral lags • Epeak vs. Eiso correlation • Similar intrinsic extinction • But they differ in other aspects: • Afterglow luminosity (specially in X-rays) • Slightly lower redshifts • More long dark bursts • Differences with short bursts are more significant • Same progenitor as long bursts but with slightly different conditions

  12. Thanks!!!

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