Journal Article

An updated gamma-ray bursts Hubble diagram

V. F. Cardone, S. Capozziello and M. G. Dainotti

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 400, issue 2, pages 775-790
Published in print December 2009 | ISSN: 0035-8711
Published online November 2009 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.15456.x
An updated gamma-ray bursts Hubble diagram

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Gamma-ray bursts (GRBs) have recently attracted much attention as a possible way to extend the Hubble diagram (HD) to very high redshift. To this aim, the luminosity (or isotropic-emitted energy) of a GRB at redshift z must be evaluated from a correlation with a distance-independent quantity so that one can then solve for the luminosity distance dL(z) and hence the distance modulus μ(z). Averaging over five different two-parameter correlations and using a fiducial cosmological model to calibrate them, Schaefer has compiled a sample of 69 GRBs with measured μ(z) which has since then been widely used to constrain cosmological parameters. Here, we update this sample through many aspects. First, we add a recently found correlation to the X-ray afterglow and use a Bayesian-inspired fitting method to calibrate the different GRB correlations known so far by assuming a fiducial Λ cold dark matter model in agreement with the recent Wilkinson Microwave Anisotropy Probe5 data. Averaging over six correlations, we end up with a new GRB HD comprising 83 objects. We also extensively explore the impact of varying the fiducial cosmological model considering how the estimated μ(z) change as a function of the (ΩM, w0, wa) parameters of the Chevallier– Polarski–Linder phenomenological dark energy equation of state. In order to avoid the need of assuming an a priori cosmological model, we present a new calibration procedure based on a model-independent local regression estimate of μ(z) using the Union Type Ia Supernovae sample to calibrate the GRBs correlations. This finally gives us a GRB HD made out of 69 GRBs whose estimated distance modulus μ(z) is almost independent of the underlying cosmological model.

Keywords: cosmology: cosmological parameters; cosmology: distance scale; gamma-rays: bursts

Journal Article.  13902 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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