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Compact object of HESS J1731-347 and its implication on neutron star matter

Prasanta Char1,2,* and Bhaskar Biswas3,†

  • *Contact author: prasanta.char@usal.es
  • †Contact author: phybhaskar95@gmail.com
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Phys. Rev. D 113, 044002 – Published 2 February, 2026

DOI: https://doi.org/10.1103/f8dq-t7ky

Abstract

In this work, we investigate the impact of the possibility of a small, subsolar mass compact star, such as the recently reported central compact object of HESS J1731-347, on the equation of state (EOS) of neutron stars. We have used a hybrid approach to the nuclear EOS developed recently where the matter around nuclear saturation density is described by a parametric expansion in terms of nuclear empirical parameters and represented in an agnostic way at higher density using piecewise polytropes. We have incorporated the inputs provided by the latest neutron skin measurement experiments from PREX-II and CREX, simultaneous mass-radius measurements of pulsars PSR J0030+0451 and PSR J0740+6620, and the gravitational wave events GW170817 and GW190425. The main results of the study show the effect of HESS J1731-347 on the nuclear parameters and neutron star observables. Our analysis yields the slope of symmetry energy L=45.71−22.11+38.18  MeV, the radius of a 1.4M⊙ star, R1.4=12.18−0.88+0.71  km, and the maximum mass of a static star, Mmax=2.14−0.17+0.26M⊙ within 90% confidence interval, respectively.

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Phys. Rev. D 113, 044002– Published 2 February, 2026
  • Received 8 October 2024
  • Accepted 14 January 2026
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