A&A 487, 853-855 (2008)
DOI: 10.1051/0004-6361:200809954

Gamma-ray burst contributions to constraining the evolution of dark energy

S. Qi^{1, 2}, F.-Y. Wang³, and T. Lu<sup>4, 2

1</sup>  Department of Physics, Nanjing University, Nanjing 210093, PR China
    e-mail: qishi11@gmail.com
²  Joint Center for Particle, Nuclear Physics and Cosmology, Nanjing University - Purple Mountain Observatory, Nanjing 210093, PR China
³  Department of Astronomy, Nanjing University, Nanjing 210093, PR China
    e-mail: fayinwang@nju.edu.cn
⁴  Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, PR China
    e-mail: t.lu@pmo.ac.cn

Received 11 April 2008 / Accepted 23 May 2008

Abstract
Aims. We explore the gamma-ray bursts' (GRBs') contributions in constraining the dark energy equation of state (EOS) at high ( 1.8 < z < 7) and at middle redshifts ( 0.5 < z < 1.8) and estimate how many GRBs are needed to get substantial constraints at high redshifts.
Methods. We estimate the constraints with mock GRBs and mock type Ia supernovae (SNe Ia) for comparisons. When constraining the dark energy EOS in a certain redshift range, we allow the dark energy EOS parameter to vary only in that redshift bin and fix EOS parameters elsewhere to -1.
Results. We find that it is difficult to constrain the dark energy EOS beyond the redshifts of SNe Ia with GRBs unless some new luminosity relations for GRBs with smaller scatters are discovered. However, at middle redshifts, GRBs have comparable contributions with SNe Ia in constraining the dark energy EOS.

Key words: cosmological parameters -- Gamma rays: bursts

© ESO 2008

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