[论文解读] Strangeon Ergostars

Haojia Xia, Shichuan Chen+3 more|arXiv (Cornell University)|Jan 5, 2026

Gamma-ray bursts and supernovae被引用 0

一句话总结

这篇论文表明 strangeon 物质支持大量、稳定且动态可维持的 ergostar 群体，能够以大约 0.01 太阳质量级别的能量抽取来供能，潜在驱动短伽玛射线暴，与传统的 EOS 不同。

ABSTRACT

The nature of the central engine powering short gamma-ray bursts (sGRBs) in binary neutron star (BNS) mergers remains a key open question in the era of multi-messenger astronomy. The ergostar hypothesis, that a rapidly rotating star with an ergoregion drives the relativistic jet, offers an alternative explanation to the black hole-accretion disk paradigm. However, previous studies based on conventional neutron star equations of state (EOSs) have shown that dynamically stable ergostars do not exist unless very extreme EOS or rotation are adopted, casting significant doubt on their astrophysical viability in reality. In this work, however, we examine this hypothesis using a phenomenological EOS of strangeon matter, i.e., condensed matter with nucleon-like units for three flavors of quarks. By constructing a large suite of uniformly rotating equilibrium models, we systematically investigate the parameter space of the stable ergostars and calculate their maximum extractable energy. In contrast to the case of conventional EOSs, we demonstrate that strangeon matter supports a vast and robust parameter space for dynamically stable ergostars, even without requiring differential rotation. We find that the extractable rotational energy from these configurations can be on the order of $0.01 M_\odot$, a reservoir sufficient to power a typical sGRB. Our results revitalize the ergostar as a viable central engine for sGRB, suggesting that BNS merger remnants composed of exotic matter could play a crucial, previously underestimated role in high-energy astrophysics.

研究动机与目标

• Motivate the search for viable ergostar central engines in BNS mergers.
• Introduce the strangeon matter equation of state as a framework for ergostar stability.
• Systematically map the ergostar parameter space and identify stability domains.
• Quantify maximum extractable rotational energy from ergostar configurations.
• Assess compatibility with multi-messenger constraints from GW170817 and NICER observations.

提出的方法

• Use a two-parameter phenomenological strangeon EOS based on Lennard-Jones interactions among strangeons.
• Solve Einstein’s equations for stationary axisymmetric spacetimes with rns to construct rotating equilibria.
• Identify ergostars via the g_tt>0 ergoregion criterion across the stellar interior.
• Apply the turning-point method to determine dynamical stability along sequences of constant angular momentum.
• Project stable ergostars onto the J-M plane and compare with an empirical J-M merger-remnant relation to assess viability.
• Compute maximum extractable energy by following energy-release paths that terminate at the minimum-mass stable ergostar along constant baryon-mass sequences.

Figure 1: Scaling relation between the central density of the minimum-mass stable ergostar ( $\rho_{c,\text{min-ergo}}$ ) and the central density of the maximum spherical mass ( $\rho_{c,\text{TOV}}$ ) for each EOS parameter set. Each color corresponds to a different fixed value of the potential dep

实验结果

研究问题

• RQ1 Can dynamically stable ergostars exist for strangeon matter without differential rotation?
• RQ2 What is the domain of stable ergostars in the J–M–ρ_c parameter space for the strangeon EOS?
• RQ3 What is the maximum extractable rotational energy from stable ergostars formed in BNS mergers?
• RQ4 Are there EOS-parameter combinations that reconcile ergostar viability with multi-messenger constraints (GW170817, NICER, etc.)?

主要发现

• Strangeon matter supports a large, robust region of dynamically stable ergostars even without differential rotation.
• Extractable rotational energy from these ergostars can be of order 0.01 M_sun c^2, sufficient to power a typical sGRB.
• A representative path yields maximum extractable energy ΔE ≈ 0.0055 M_sun for a specific case geometry.
• Minimum-mass ergostars that can form from BNS mergers can have M ≈ 2.76–3.04 M_sun depending on EOS parameters (ε̃ and n_sur).
• Stiffer EOSs (larger ε̃) generally expand the ergostar domain and energy budget, though nontrivial interactions with the merger line exist.
• Intersection with the empirical merger-remnant line indicates that GW170817-like events can naturally produce transient ergostars with M ≈ 2.6 M_sun and ΔE ~ 0.02 M_sun c^2 for certain parameter choices.
• The softest EOS within the explored space can yield larger ΔE in some regimes, highlighting nontrivial interplay between stability boundaries and merger constraints.

Figure 2: Scaling relation between the gravitational mass of the minimum-mass stable ergostar ( $M_{\text{min-ergo}}$ ) and the maximum spherical (TOV) mass ( $M_{\text{TOV}}$ ). As in the previous figure, each color corresponds to a fixed value of $\tilde{\epsilon}$ . The solid points represent ind