Dense Stars with Weak Magnetic Fields

• Main Authors: CHIN-WEN CHEN, 陳錦文
• Other Authors: W-Y. Pauchy Hwang
• Format: Others
• Language: en_US
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/69591722855313921583

碩士 === 國立臺灣大學 === 物理學研究所 === 89 === Abstract In this thesis, we investigate the influence of weak magnetic fields on dense stars (neutron stars & quark stars). We explore the possibility that such dense stars have weak magnetic fields (γ= B/Bcn =0, 0.01, 0.05, 0.1, 0.2) and how their stability and structure are affected. We study properties of a degenerate ideal neutron star and strange star with and without the weak magnetic fields. First, we discuss three fundamental equations: the mass equation; the Tolman-Oppenheimer-Volkoff equation; and the equa-tion of state (EOS). We then apply an Euler-MacLaurin expansion (Ker-nan, Starkman, & Vachaspati 1996) [1] in the weak magnetic field limit to modify the EOS. We use the numerical integration method to obtain the Chandrasekhar limit of the dense stars. The Chandrasekhar limit (M0) of the neutron star is around 0.66 times the solar mass in the absence of a magnetic field. As the strengths of magnetic field varies with γ= 0.01, 0.05, 0.1, 0.2, the Chandrasekhar limit (MB) of neutron stars ranges from 0.66, 0.69, 0.79, 1.22 times the solar mass, respectively. The rate of in-crease for the maximum neutron star mass is given approximately by , ( γ ≤ 0.2 ). The Chandrasekhar limit (M0) of the quark star is around 1.07 times the solar mass in the absence of a magnetic field. As the strengths of mag-netic field varies with γ= 0.01, 0.05, 0.1, 0.2, the Chandrasekhar limit (MB) of quark stars ranges from 1.07, 1.09, 1.16, 2.15 times the solar mass, re-spectively. The rate of increase for the maximum quark star mass is esti-mated to be , ( γ ≤ 0.2 ). The neutron stars and the quark stars with relatively weak magnetic fields (γ< 0.1) hardly change the Chandrasekhar limit. Gibb’s free energy may be used as a criterion to determine which case the stars will be more sta-ble. The Gibb's free energy for both neutron stars and quark stars with magnetic fields is always lower, so they are more stable.