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Quarkyonic Neutron Stars as Candidates for the GW230529 Mass-Gap Object

Jeet Amrit Pattnaik, S. K. Patra

TL;DR

The paper investigates whether quarkyonic equations of state (EOS) can explain compact objects in the $2.5$–$4.5$ $M_{ m sun}$ mass-gap observed in GW230529. By embedding a quarkyonic phase within a relativistic mean-field (RMF) framework and varying the transition density $n_t$ and confinement scale, the authors compute mass–radius sequences that remain causal and stable. They find that several quarkyonic EOSs produce stable non-rotating stars in the mass-gap with radii around $13$–$15$ km, including a maximum mass near $2.95$ $M_{ m sun}$ for the stiffest case, while higher $n_t$ (e.g., 0.5 fm$^{-3}$) tends to reduce the maximum mass. The results suggest that the heavier GW230529 component could be a massive quarkyonic neutron star rather than a black hole, offering a natural mechanism to populate the mass gap while constraining dense-matter EOS models.

Abstract

We examine whether quarkyonic equations of state (EOS) can account for compact objects in the $2.5$-$4.5\,M_\odot$ mass range reported for the GW230529 gravitational-wave event. The pressure-energy density and mass-radius (M-R) relations obtained from quarkyonic EOS models indicate a significant stiffening at high densities, allowing stable configurations beyond $2.5\,M_\odot$. The predicted M-R sequences extend into the GW230529 mass window while maintaining radii in the range of $\approx 13$-$15$~km, suggesting that quarkyonic stars can naturally populate the so-called compact object mass gap. These results imply that the heavier component of GW230529 could plausibly be a massive quarkyonic neutron star rather than a low-mass black hole.

Quarkyonic Neutron Stars as Candidates for the GW230529 Mass-Gap Object

TL;DR

The paper investigates whether quarkyonic equations of state (EOS) can explain compact objects in the – mass-gap observed in GW230529. By embedding a quarkyonic phase within a relativistic mean-field (RMF) framework and varying the transition density and confinement scale, the authors compute mass–radius sequences that remain causal and stable. They find that several quarkyonic EOSs produce stable non-rotating stars in the mass-gap with radii around – km, including a maximum mass near for the stiffest case, while higher (e.g., 0.5 fm) tends to reduce the maximum mass. The results suggest that the heavier GW230529 component could be a massive quarkyonic neutron star rather than a black hole, offering a natural mechanism to populate the mass gap while constraining dense-matter EOS models.

Abstract

We examine whether quarkyonic equations of state (EOS) can account for compact objects in the - mass range reported for the GW230529 gravitational-wave event. The pressure-energy density and mass-radius (M-R) relations obtained from quarkyonic EOS models indicate a significant stiffening at high densities, allowing stable configurations beyond . The predicted M-R sequences extend into the GW230529 mass window while maintaining radii in the range of -~km, suggesting that quarkyonic stars can naturally populate the so-called compact object mass gap. These results imply that the heavier component of GW230529 could plausibly be a massive quarkyonic neutron star rather than a low-mass black hole.

Paper Structure

This paper contains 4 sections, 2 figures, 1 table.

Table of Contents

  1. Introduction
  2. Theoretical Frameworks
  3. Results and Discussions
  4. Summary and Conclusions

Figures (2)

  • Figure 1: Pressure as a function of energy density for the quarkyonic equations of state at a transition density $n_t = 0.3,0.4,0.5~\mathrm{fm^{-3}}$ with confinement scales $\Lambda_{\mathrm{cs}} = 800$ and $1400$ MeV for the G3 and IOPB models.
  • Figure 2: M-R relations for the EoSs shown in Fig. \ref{['fig:eos']}, along with the GW230529 observational data GW230529.