The Plateau of Gamma-ray Burst: Hint for the Solidification of Quark Matter?

TL;DR

This paper proposes that the phase transition of newborn quark stars from liquid to solid releases latent heat, which injects energy into GRB afterglows, explaining the shallow decay and abrupt falloff in light curves.

Contribution

It introduces a novel mechanism linking quark star solidification and GRB afterglow features, providing a new explanation for the shallow decay segment.

Findings

Latent heat during quark star solidification is about 10^{51} ergs.

The timescale of latent heat emission matches observed GRB afterglow features.

Energy injection from quark star phase transition can produce observed light curve behaviors.

Abstract

The origin of the shallow decay segment in gamma-ray burst's (GRB) early light curves remains a mystery, especially those cases with a long-lived plateau followed by an abrupt falloff. In this paper, we propose a mechanism to understand the origin of the abrupt falloff after plateau by considering solidification of newborn quark stars with latent heat released as energy injection to GRB afterglow. We estimate the total latent heat released during the phase transition of quark stars from liquid to solid states, to be order of ~ 10^{51}ergs, which is comparable to the emission energy in the shallow decay segment. We also estimate the time scale of radiating the latent heat through thermal photon emission, and find that the time scale agrees with observations. Based on our estimation, we analyze the process of energy injection to GRB afterglow. We show that the steady latent heat of quark star phase transition would continuously inject into GRB afterglow in a form similar to that of a Poyntingflux- dominated outflow and naturally produce the shallow decay phase and the abrupt falloff after plateau. We conclude that the latent heat of quark star phase transition would be an important contribution to the shallow decay radiation in GRB afterglow, and would explain the general features of GRB light curves (including the plateau), if pulsar-like stars are really (solid) quark stars.