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arXiv · 2512.05099

PSR J0952-0607: Tightening a Record-High Neutron Star Mass

Roger W. Romani·Maya Beleznay·Alexei V. Filippenko·Thomas G. Brink·WeiKang Zheng
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Abstract

We report on new orbit-minimum photometry and revised radial-velocity fitting that provide an improved measurement of the mass of the neutron star (NS) in pulsar PSR~J0952$-$0607 at $M_NS = 2.35\pm 0.11 M_\odot$. With its fast spin and unusually low magnetic field, this NS has evidently experienced unusual evolution, likely connected with its high mass, which is now $2.5\sigma$ above that of the heaviest pulsar with a white dwarf companion, as measured by Shapiro delay techniques. By tightening the mass measurement, we also raise the maximum (commonly called Tolman-Oppenheimer-Volkoff) NS mass to $M_{\rm TOV} > 2.27\,M_\odot$$(2.12\,M_\odot)$ at $1\sigma$$(3\sigma)$ confidence, which improves bounds on the dense-matter equation of state. While the statistical error decreases and systematic issues should be modest, uncertainties remain; we comment briefly on these factors and prospects for further improvement.

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Roger W. Romani, Maya Beleznay, Alexei V. Filippenko, Thomas G. Brink, WeiKang Zheng. 2025-12-04. PSR J0952-0607: Tightening a Record-High Neutron Star Mass. https://arxiv.org/abs/2512.05099

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