X-ray light curve in GRB 170714A: evidence for quark star?

TL;DR

This paper proposes a novel model where a hyper-massive quark star formed from neutron star merger explains the complex X-ray light curve features of GRB 170714A, including plateaus and a bump.

Contribution

It introduces the post-merger quark star model as an explanation for unique X-ray features in GRB 170714A, linking it to neutron star mergers and quark star physics.

Findings

The model explains the two plateaus and bump in the X-ray light curve.

Magnetic fields of ~10^{15} G can be generated during the quark star phase.

The model predicts observable gravitational waves and electromagnetic signals.

Abstract

Two plateaus and one following bump in the X-ray light curve of GRB 170714A have been detected by the \textit{Swift}/X-Ray Telescope, which could be very meaningful for the central engine of gamma-ray bursts (GRBs), implying that the origin of this burst might be different from that of other ultra-long GRBs. We propose that merging two neutron stars into a hyper-massive quark star (QS) and then collapsing into a black hole (BH), with a delay time around $10^4$~s, could be responsible for those X-ray components. The hyper-massive QS is initially in a fluid state, being turbulent and differentially rotating, but would be solidified and release its latent heat injected into the GRB fireball (lasting about $10^3$~s during the liquid-solid phase transition). Magnetic field as high as $\sim 10^{15}$~G could be created by dynamo action of the newborn liquid QS, and a magnetar-like central engine (after solidification) supplies significant energy for the second plateau. More energy could be released during a fall-back accretion after the post-merger QS collapses to a BH, and the X-ray bump forms. This post-merger QS model might be tested by future observations, with either advanced gravitational wave detectors (e.g., advanced LIGO and VIRGO) or X-ray/optical telescopes.