Discovery of a Universal Correlation For Long and Short GRBs and Its Application on the Study of Luminosity Function and Formation Rate

TL;DR

This paper discovers a universal correlation involving prompt emission properties of both long and short GRBs, enabling unbiased redshift estimation and insights into their luminosity functions and formation rates, suggesting similar radiation processes.

Contribution

The paper introduces a universal correlation applicable to both long and short GRBs based on prompt emission properties, which aids in redshift estimation and understanding GRB populations.

Findings

Universal correlation: L_iso ∝ E_peak^{1.94} T_{0.45}^{0.37}

Luminosity function for short GRBs: L_0^{-0.63} for dim, L_0^{-1.96} for bright

Local formation rate of short GRBs: ~15 Gpc^{-3} yr^{-1}

Abstract

Gamma-ray bursts (GRBs) are known to be the most violent explosions in the universe, and a variety of correlations between observable GRB properties have been proposed in literature, but none of these correlations is valid for both long GRBs and short GRBs. In this paper we report the discovery of a universal correlation which is suitable for both long and short GRBs using three prompt emission properties of GRBs, i.e. the isotropic peak luminosity $L_{\rm iso}$, the peak energy of the time-integtated prompt emission spectrum $E_{\rm peak}$, and the "high signal" timescale $T_{\rm 0.45}$, $L_{\rm iso} \propto E_{\rm peak}^{1.94} T_{0.45}^{0.37}$. This universal correlation just involves properties of GRB prompt emission and does not require any information of afterglow phase, which can be used as a relatively unbiased redshift estimator. Here we use this correlation to estimate the pseudo-redshifts for short Gamma Ray Bursts and then use Lynden-Bell method to obtain a non-parametric estimate of their luminosity function and formation rate. The luminosity function is $\psi(L_0)\propto{L_0^{-0.63\pm{0.07}}}$ for dim SGRBs and $\psi(L_0)\propto{L_0^{-1.96\pm{0.28}}}$ for bright SGRBs, with the break point $6.95_{-0.76}^{+0.84}\times10^{50} erg/s$. The local formation rate of SGRBs is about 15 events $\rm Gpc^{-3}yr^{-1}$ . This universal correlation may have important implications for GRB physics, implying that the long and short GRBs should share similar radiation processes.