Tracing Dark Energy History with GammaRay Bursts
Abstract
Observations of gammaray bursts up to z ∼ 9 are best suited to study the possible evolution of the universe equation of state at intermediate redshifts. We apply the Combo relation to a sample of 174 gammaray bursts to investigate possible evidence of evolving dark energy parameter w(z). We first build a gammaray burst Hubble's diagram and then we estimate the set (Ω_{m}, Ω_{Λ}) in the framework of flat and nonflat ΛCDM paradigm. We then get bounds over the wCDM model, where w is thought to evolve with redshift, adopting two priors over the Hubble constant in tension at 4.4σ, i.e., H_{0} = (67.4 ± 0.5) km s^{1} Mpc^{1} and H_{0} = (74.03 ± 1.42) km s^{1} Mpc^{1}. We show our new sample provides tighter constraints on Ω_{m} since at z ≤ 1.2 we see that w(z) agrees within 1σ with the standard value w = 1. The situation is the opposite at larger z, where gammaray bursts better fix w(z) that seems to deviate from w = 1 at 2σ and 4σ level, depending on the redshift bins. In particular, we investigate the w(z) evolution through a piecewise formulation over seven redshift intervals. From our fitting procedure we show that at z ≥ 1.2 the case w < 1 cannot be fully excluded, indicating that dark energy's influence is not negligible at larger z. We confirm the Combo relation as a powerful tool to investigate cosmological evolution of dark energy. Future space missions will significantly enrich the gammaray burst database even at smaller redshifts, improving de facto the results discussed in this paper.
 Publication:

The Astrophysical Journal
 Pub Date:
 February 2021
 DOI:
 10.3847/15384357/abd254
 arXiv:
 arXiv:2012.03392
 Bibcode:
 2021ApJ...908..181M
 Keywords:

 Standard candles;
 Dark energy;
 Gammaray bursts;
 1563;
 351;
 629;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 Astrophysics  High Energy Astrophysical Phenomena
 EPrint:
 10 pages, 7 figures, ApJ submitted