Addressing the circularity problem in the E p − E iso correlation of gamma-ray bursts.

We here propose a new model-independent technique to overcome the circularity problem affecting the use of gamma-ray bursts (GRBs) as distance indicators through the use of E p−Eiso correlation. We calibrate the E p −E iso correlation and find the GRB distance moduli that can be used to constrain dark energy models. We use observational Hubble data to approximate the cosmic evolution through Bézier parametric curve obtained through the linear combination of Bernstein basis polynomials. In doing so, we build up a new data set consisting of 193 GRB distance moduli. We combine this sample with the supernova JLA data set to test the standard ΛCDM model and its w CDM extension. We place observational constraints on the cosmological parameters through Markov Chain Monte Carlo numerical technique. Moreover, we compare the theoretical scenarios by performing the Akaike and Deviance Information statistical criteria.the 2σ level, while for the w CDM model we obtain |$\Omega _m=0.34^{+0.13}_{-0.15}$| and |$w=-0.86^{+0.36}_{-0.38}$| at the 2σ level. Our analysis suggests that ΛCDM model is statistically favoured over the w CDM scenario. No evidence for extension of the ΛCDM model is found. [ABSTRACT FROM AUTHOR]