High-Redshift Gamma-Ray Bursts: Observational Signatures of Superconducting Cosmic Strings?

The high-redshift gamma-ray bursts (GRBs), GRBs 080913 and 090423, challenge the conventional GRB progenitor models by their short durations, typical for short GRBs, and their high energy releases, typical for long GRBs. Meanwhile, the GRB rate inferred from high-redshift GRBs also remarkably exceeds the prediction of the collapsar model, with an ordinary star formation history. We show that all these contradictions could be eliminated naturally, if we ascribe some high-redshift GRBs to electromagnetic bursts of superconducting cosmic strings. High-redshift GRBs could become a reasonable way to test the superconducting cosmic string model because the event rate of cosmic string bursts increases rapidly with increasing redshifts, whereas the collapsar rate decreases.

Figure 1

The cosmic star formation history. The SFR data (diamonds) inferred from the high-redshift GRBs [9] obviously deviate from the star formation history (dashed line) given by 10, which is obtained by fitting the compiled SFR data inferred from galaxies (circles). For a comparison, we also exhibit the newer data inferred from the high-redshift Lyman break galaxies (triangles) [11] and Lyman-$\alpha$ emitters (crosses) [27]. The dash-dotted lines represent the effective star formation history inferred from the CSGRBs with different values of $A$ and the solid line represents the combination of the dash and dash-dotted line for $A=0.1$.