X-ray Plateaus in Gamma-Ray Burst Afterglows and Their Application in Cosmology

Abstract

For gamma-ray bursts (GRBs) with a plateau phase in the X-ray afterglow, a so called $L-T-E$ correlation has been found which tightly connects the isotropic energy of the prompt GRB ($E_{{\hat{I}}^3,\mathrm{iso}}$) with the end time of the X-ray plateau ($T_a$) and the corresponding X-ray luminosity at the end time ($L_X$). Here we show that there is a clear redshift evolution in the correlation. Furthermore, since the power-law indices of $L_X$ and $E_{{\hat{I}}^3,\mathrm{iso}}$ in the correlation function are almost identical, the $L-T-E$ correlation is insensitive to cosmological parameters and cannot be used as a satisfactory standard candle. On the other hand, based on a sample including 121 long GRBs, we establish a new three parameter correlation that connects $L_X$, $T_a$ and the spectral peak energy $E_{\mathrm{p}}$, i.e. the $L-T-E_{\mathrm{p}}$ correlation. This correlation strongly supports the so-called Combo-relation established by Izzo et al. (2015). After correcting for the redshift evolution, we show that the de-evolved $L-T-E_{\mathrm{p}}$ correlation can be used as a standard candle. By using this correlation alone, we are able to constrain the cosmological parameters as $\hat{I}{\text{c◯}}_m=0.389_{-0.141}^{+0.202}$ ($1\ddot{I}ƒ$) for the flat $\hat{I}›$CDM model, or $\hat{I}{\text{c◯}}_m=0.369_{-0.191}^{+0.217}$, $w=-0.966_{-0.678}^{+0.513}$ ($1\ddot{I}ƒ$) for the flat $w$CDM model. Combining with other cosmological probes, more accurate constraints on the cosmology models are presented.

26 pages, 13 figures, ApJ, accepted