TY - JOUR

T1 - Effects of symmetry energy on the radius and tidal deformability of neutron stars in the relativistic mean-field model

AU - Hu, Jinniu

AU - Bao, Shishao

AU - Zhang, Ying

AU - Nakazato, Ken'ichiro

AU - Sumiyoshi, Kohsuke

AU - Shen, Hong

N1 - Funding Information:
This work was supported in part by the National Natural Science Foundation of China (Grants No. 11775119, No. 11675083, and No. 11405116), the Natural Science Foundation of Tianjin, and the China Scholarship Council (Grant No. 201906205013 and No. 201906255002). This work is supported by a Grant-in-Aid for Scientific Research (19K03837, 15K05093) and a Grant-in-Aid for Scientific Research on Innovative Areas “Gravitational wave physics and astronomy: Genesis” (17H06357, 17H06365) and “Unraveling the history of the universe and matter evolution with underground physics” (19H05811) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. K.S. acknowledges high-performance computing resources at KEK, JLDG, RCNP, YITP, and UT. This work was partly supported by the research programs at the K-computer of the RIKEN AICS, the HPCI Strategic Program of Japanese MEXT, “Priority Issue on Post-K computer” (Elucidation of the Fundamental Laws and Evolution of the Universe), and the Joint Institute for Computational Fundamental Sciences (JICFus).
Publisher Copyright:
© 2020 The Author(s) 2020. Published by Oxford University Press on behalf of the Physical Society of Japan.

PY - 2020/4/13

Y1 - 2020/4/13

N2 - The radii and tidal deformabilities of neutron stars are investigated in the framework of the relativistic mean-field (RMF) model with different density-dependent behaviors of symmetry energy. To study the effects of symmetry energy on the properties of neutron stars, ω meson and ρ meson coupling terms are included in a popular RMF Lagrangian, i.e., the TM1 parameter set, which is adopted for the widely used supernova equation of state (EoS) table. The coupling constants relevant to the vector-isovector meson, ρ, are refitted by a fixed symmetry energy at subsaturation density and its slope at saturation density, while other coupling constants remain the same as the original ones in TM1 so as to update the supernova EoS table. The radius and mass of maximum neutron stars are not so sensitive to the symmetry energy in these family TM1 parameterizations. However, the radii in the intermediate-mass region are strongly correlated with the slope of symmetry energy. Furthermore, the dimensionless tidal deformabilities of neutron stars are also calculated within the associated Love number, which is related to the quadrupole deformation of the star in a static external tidal field and can be extracted from the observation of a gravitational wave generated by a binary star merger. We find that its value at 1.4 M⊙ has a linear correlation to the slope of symmetry energy, unlike that previously studied. With the latest constraints of tidal deformabilities from the GW170817 event, the slope of symmetry energy at nuclear saturation density should be smaller than 60 MeV in the family TM1 parameterizations. This fact supports the usage of a lower symmetry energy slope for the updated supernova EoS, which is applicable to simulations of neutron star mergers. Furthermore, an analogous analysis is also done within the family IUFSU parameter sets. It is found that the correlations between the symmetry energy slope with the radius and tidal deformability at 1.4 M⊙ have very similar linear relations in these RMF models.

AB - The radii and tidal deformabilities of neutron stars are investigated in the framework of the relativistic mean-field (RMF) model with different density-dependent behaviors of symmetry energy. To study the effects of symmetry energy on the properties of neutron stars, ω meson and ρ meson coupling terms are included in a popular RMF Lagrangian, i.e., the TM1 parameter set, which is adopted for the widely used supernova equation of state (EoS) table. The coupling constants relevant to the vector-isovector meson, ρ, are refitted by a fixed symmetry energy at subsaturation density and its slope at saturation density, while other coupling constants remain the same as the original ones in TM1 so as to update the supernova EoS table. The radius and mass of maximum neutron stars are not so sensitive to the symmetry energy in these family TM1 parameterizations. However, the radii in the intermediate-mass region are strongly correlated with the slope of symmetry energy. Furthermore, the dimensionless tidal deformabilities of neutron stars are also calculated within the associated Love number, which is related to the quadrupole deformation of the star in a static external tidal field and can be extracted from the observation of a gravitational wave generated by a binary star merger. We find that its value at 1.4 M⊙ has a linear correlation to the slope of symmetry energy, unlike that previously studied. With the latest constraints of tidal deformabilities from the GW170817 event, the slope of symmetry energy at nuclear saturation density should be smaller than 60 MeV in the family TM1 parameterizations. This fact supports the usage of a lower symmetry energy slope for the updated supernova EoS, which is applicable to simulations of neutron star mergers. Furthermore, an analogous analysis is also done within the family IUFSU parameter sets. It is found that the correlations between the symmetry energy slope with the radius and tidal deformability at 1.4 M⊙ have very similar linear relations in these RMF models.

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U2 - 10.1093/ptep/ptaa016

DO - 10.1093/ptep/ptaa016

M3 - Article

AN - SCOPUS:85084433578

VL - 2020

JO - Progress of Theoretical and Experimental Physics

JF - Progress of Theoretical and Experimental Physics

SN - 2050-3911

IS - 4

M1 - 043D01

ER -