Hyperon Effects on the Spin Parameter of Rotating Neutron Stars

Based on the equations of state from the relativistic mean field theory without and with the inclusion of strangeness-bearing hyperons, we study the dimensionless spin parameter j = cJ/（GM2） of uniformly rotat- ing neutron stars. It is shown that the maximum value of the spin parameter jmax of a neu...

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Bibliographic Details
Published inChinese physics letters Vol. 32; no. 11; pp. 31 - 34
Main Author 亓斌 张乃波 王守宇 孙保元
Format Journal Article
LanguageEnglish
Published 01.11.2015
Subjects
Accretion disks
Equations of state
Field theory
Hyperons
Mathematical models
Neutron stars
Stars
Stellar rotation
中子星
准周期振荡
恒星质量
旋转参数
旋转频率
状态方程
相对论平均场理论
超子
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ISSN0256-307X
1741-3540
1741-3540
DOI10.1088/0256-307X/32/11/112101

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Summary:Based on the equations of state from the relativistic mean field theory without and with the inclusion of strangeness-bearing hyperons, we study the dimensionless spin parameter j = cJ/（GM2） of uniformly rotat- ing neutron stars. It is shown that the maximum value of the spin parameter jmax of a neutron star rotating at the Keplerian frequency fK is .jmax - 0.7 when the star mass M 〉 0.SM⊙, which is sustained for various versions of equations of state without and with hyperons. The relationship between j and the scaled rotation frequency f /fK is found to be insensitive to the star mass or the adopted equation of state in the models without hyperons. However, the emergence of byperons in neutron stars will lead to an uncertainty of the spin parameter j, which in turn could generate a complexity in the theoretical study of the quasi-periodic oscillations observed in disk-accreting compact-star systems.
Bibliography:11-1959/O4
QI Bin, ZHANG Nai-Bo, WANG Shou-Yu, SUN Bao-Yuan（ 1Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, Institute of Space Sciences, Shandong University, Weihai 264209 2School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 3Key Laboratory of Special Function Materials and Structure Design of Ministry of Education, Lanzhou 730000）
Based on the equations of state from the relativistic mean field theory without and with the inclusion of strangeness-bearing hyperons, we study the dimensionless spin parameter j = cJ/（GM2） of uniformly rotat- ing neutron stars. It is shown that the maximum value of the spin parameter jmax of a neutron star rotating at the Keplerian frequency fK is .jmax - 0.7 when the star mass M 〉 0.SM⊙, which is sustained for various versions of equations of state without and with hyperons. The relationship between j and the scaled rotation frequency f /fK is found to be insensitive to the star mass or the adopted equation of state in the models without hyperons. However, the emergence of byperons in neutron stars will lead to an uncertainty of the spin parameter j, which in turn could generate a complexity in the theoretical study of the quasi-periodic oscillations observed in disk-accreting compact-star systems.
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ISSN:0256-307X
1741-3540
1741-3540
DOI:10.1088/0256-307X/32/11/112101