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, [Formula: see text]–[Formula: see text][Formula: see text]km, and that calculated by TW99 is the largest, [Formula: see text]–[Formula: see text][Formula: see text]km. 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 [Formula: see text], the central field strength [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] of mesons [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text], the central energy density [Formula: see text], and the central pressure [Formula: see text] 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, [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text]) appear inside PNS PSR J0740+6620 whereas those with NL1 and NL2 show that hyperon [Formula: see text] 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.