Antikaons and higher order couplings in the relativistic mean-field study of neutron stars

Abstract

We investigate the role of higher order couplings, along with the condensation of antikaons (K − andK 0 ), on the properties of neutron star (NS). We employ extended versions of the relativistic mean-field model, in which kaon-nucleon and nucleon-nucleon interactions are taken on the same footing. We find that the onset of condensation of K − andK 0 highly depends not only on the strength of optical potential but also on the new couplings. The presence of antikaons leads to a softer equation of state and makes the neutron star core symmetric and lepton-deficient. We show that these effects strongly influence the mass-radius relation as well as the composition of neutron star. We also show that the recently observed 1.97±.04 solar mass NS can be explained in three ways: (i) a stiffer EoS with both antikaons, (ii) a relatively soft EoS with K − and (iii) a softer EoS without antikaons.

Impact of hyperons and antikaons in an extended relativistic mean-field description of neutron stars

“…Hyperons have a much stronger effect in reducing the mass than do antikaons. In the absence of hyperons, antikaons have a significant role to play [23,37]. In the presence of hyperons, the mass marginally changes with the inclusion of antikaons.…”

“…Only the ω field and the electron chemical potential are influenced by the onset of antikaons in the cases of G2 and IUFSU whereas the ρ field also changes in other cases. In the cases of G1 and NL3 the third kink in μ e represents the onset ofK 0 , which enhances the neutron-proton symmetry [37] and leads to a strong suppression in the corresponding ρ fields. NL3 yields the stiffest ω meson field in both phases and hence yields the stiffest EoS among all the parameter sets.…”

“…The results from the HNA phase (with U K = −120 MeV) suggest negligible influence of antikaons (except for the case of NL3, where K − appears at ρ ∼ 4ρ 0 ), which means the results are the same as for the HN phase. It has to be noted that U K = −120 MeV is suggested by the chiral models [46] and was used in some of our previous works [23,37] with antikaons but without the hyperons. When hyperons are not assumed to be present, even a weaker U K resulted [23] in a strong influence of antikaons in the EoS of NS matter despite the softening role played by the higher order couplings of the extended RMF models.…”

“…In our earlier calculations, we described NS matter with the K − [23] and with K − andK 0 [37] condensation. Here we extend these models further with the inclusion of hyperons.…”

“…Recently, we have studied the role of antikaons [23,37] in the presence of higher order couplings of the extended RMF models. In the present work we consider * nehaguptaiitr@gmail.com both hyperons and antikoans in the recent versions of the extended RMF models to study NS properties.…”