Constraining the Equation of State of Neutron Stars through GRB X-Ray Plateaus

Abstract

The unknown equation of state (EoS) of neutron stars (NSs) is puzzling because of rich non-perturbative effects of strong interaction there. A method to constrain the EoS by using the detected X-ray plateaus of gamma-ray bursts (GRBs) is proposed in this paper. Observations show some GRB X-ray plateaus may be powered by strongly magnetized millisecond NSs. The properties of these NSs should then satisfy: (i) the spin-down luminosity of these NSs should be brighter than the observed luminosity of the X-ray plateaus; (ii) the total rotational energy of these NSs should be larger than the total energy of the X-ray plateaus. Through the case study of GRB 170714A, the moment of inertia of NSs is constrained as $I>1.0\times 10^{45}{\left(\frac{P_{\mathrm{cri}}}{1\mathrm{ms}}\right)}^2\mathrm{g}\cdot \mathrm{c}{\mathrm{m}}^2$, where $P_{\mathrm{cri}}$ is the critical rotational period that an NS can achieve. The constraint of the radii of NSs according to GRB 080607 is shown in Table 1.

6 pages, 2 figute, The Astrophysical Journal, 886:87, 2019 December 1, https://doi.org/10.3847/1538-4357/ab4901