Analysis of Neutron Star fmode Oscillations in General Relativity with Spectral Representation of Nuclear Equations of State
Abstract
We study quasinormal fmode oscillations in neutron star (NS) interiors within a linearized general relativistic formalism. We utilize approximately 9000 nuclear equations of state (EOSs) using spectral representation techniques, incorporating constraints on nuclear saturation properties, chiral effective field theory for pure neutron matter, and perturbative quantum chromodynamics for densities pertinent to NS cores. The median values of the fmode frequency, ν _{ f } (damping time, τ _{ f }) for NSs with masses ranging from 1.4 to 2.0 M _{⊙} lie between 1.80 and 2.20 kHz (0.13–0.22 s) for our entire EOS set. Our study reveals a weak correlation between fmode frequencies and individual nuclear saturation properties, prompting the necessity for more intricate methodologies to unveil multiparameter relationships. We observe a robust linear relationship between the radii and fmode frequencies for different NS masses. Leveraging this correlation alongside NICER observations of PSR J0740+6620 and PSR J0030+0451, we establish constraints that exhibit partial and minimal overlap for observational data from Riley et al. and Miller et al., respectively, with our nucleonic EOS data set. Moreover, NICER data align closely with the radius and frequency values for a few hadron–quark hybrid EOS models. This indicates the need to consider additional exotic particles such as deconfined quarks at suprasaturation densities. We conclude that future observations of the radius or fmode frequency for more than one NS mass, particularly at the extremes of the viable NS mass scale, would either rule out nucleononly EOSs or provide definitive evidence in its favor.
 Publication:

The Astrophysical Journal
 Pub Date:
 June 2024
 DOI:
 10.3847/15384357/ad43e6
 arXiv:
 arXiv:2312.02061
 Bibcode:
 2024ApJ...968..124G
 Keywords:

 Neutron stars;
 Quasinormal modes;
 1108;
 1320;
 Astrophysics  High Energy Astrophysical Phenomena;
 General Relativity and Quantum Cosmology;
 Nuclear Theory
 EPrint:
 21 pages, 10 figures, 4 tables, Accepted in Astrophysical Journal