Redshift catalog for most swift gamma-ray bursts

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Conference Proceeding

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The redshifts of long-duration Gamma-Ray Bursts (GRBs) is an important issue in the field of study, and unfortunately only 30% of Swift GRBs have their redshifts measured from optical spectroscopy. We are using the luminosity relations, wherein some measurable light curve or spectral property (e.g., spectral lag τlag or Epeak) is well correlated with the burst luminosity, along with some adopted cosmology, to measure the redshift of bursts without optical spectroscopy. By applying our method to the bursts with spectroscopic redshifts, we came up with the result that our average error in redshift is 26% and the spectroscopic redshifts falling inside our 1-σ range for 63% of the GRBs. In this paper, we applied the same method to all the long-duration Swift bursts, and presented our redshift catalog for approximately 200 Swift bursts up to May 2007 above a low brightness threshold, each with accurately propagated error bars. Our complete catalog can be used for various demographic studies (without the complex selection effects of optical spectroscopy). From our results we see that the spectroscopic redshifts have been biased to z<2, and by using all the detected bursts, we are getting rid of the spectroscopic selection effect. Also, we found three possible high redshift GRBs, with their 1-σ lower limit much larger than z=7. Unfortunately, as their 2-σ and 3-σ redshift lower limit drop down below z=7, we cannot claim that they are definitely high redshift bursts. © 2008 American Institute of Physics.

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AIP Conference Proceedings

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