A key factor to the spin parameter of uniformly rotating compact stars: crust structure

摘要: We study the key factor to determine dimensionless spin parameter $j\equiv cJ/(GM^2)$ of different kinds uniformly rotating compact stars, including traditional neutron hyperonic and hybrid check reliability results on various types equations state dense matter. The from relativistic mean field theory MIT bag model are adopted simulate stars. Numerical calculations rigidly stars performed using RNS code in framework general relativity by solving Einstein for stationary axis-symmetric spacetime. crust structure is found be a maximum value $j_{\rm max}$. For with inclusion crust, max}\sim 0.7$ sustained $M>0.5 M_{\odot}$, insensitive mass star selected state. without structure, max}$ lies range $[0.7, 1.0]$. Thus, not $j>0.7$ but $j>1$ could treated as candidate criterion distinguish strange quark other Furthermore, universal formula $j=0.48(f/f_K)^3-0.42(f/f_K)^2+0.63(f/f_K)$ suggested calculate at any rotational frequency all $M>0.5M_{\odot}$.