Effect of nucleon coupling constants on properties of proto neutron star PSR J0740+6620
Abstract
The properties of proto neutron star (PNS) PSR J0740+6620 are studied with the relative mean field theory. In our calculations, we find that five nucleon coupling parameters (DD-MEI, NL1, NL2, TW99 and GM1) can give the mass of the PNS PSR J0740+6620. The radius of PNS PSR J0740+6620 calculated by GM1 is the smallest, R=14.63–13.44km, and that calculated by TW99 is the largest, R=17.46–17.07km. The radius calculated by other nucleon coupling parameters is between the two. We find that properties of PNS PSR J0740+6620 calculated by different nucleon coupling parameters are different. The central baryon density ρc, the central field strength σ0c, ω0c, σ∗0c and ϕ0c of mesons σ, ω, σ∗ and ϕ, the central energy density 𝜀c, and the central pressure pc calculated by GM1 are all the largest among the five sets of nucleon coupling parameters. The calculations with DD-MEI, TW99 and GM1 show that eight baryons (n, p, Λ, Σ−, Σ0, Σ+, Ξ− and Ξ0) appear inside PNS PSR J0740+6620 whereas those with NL1 and NL2 show that hyperon Σ+ does not appear. The relative particle density of baryons inside PNS PSR J0740+6620 is also very different as the PNS is calculated with different nucleon coupling constants.
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