We consider the so-called hyperon puzzle of neutron star (NS). We employ Skyrme force models for the description of in-medium nucleon-nucleon (NN), nucleon-Lambda hyperon (Nλ) and Lambda-Lambda (λλ) interactions. A phenomenological finite-range force (FRF) for the λλ interaction is considered as well. Equation of state (EoS) of NS matter is obtained in the framework of density functional theory, and Tolman-Oppenheimer-Volkoff (TOV) equations are solved to obtain the mass-radius relations of NSs. It has been generally known that the existence of hyperons in the NS matter is not well supported by the recent discovery of large-mass NSs (M ≃ 2M⊙) since hyperons make the EoS softer than the one without them. For the selected interaction models, Nλ interactions reduce the maximum mass of NS by about 30%, while λλ interactions can give about 10% enhancement. Consequently, we find that some Skyrme force models predict the maximum mass of NS consistent with the observation of 2M⊙ NSs, and at the same time satisfy observationally constrained mass-radius relations.
Bibliographical noteFunding Information:
∗Rare Isotope Science Project, Institute for Basic Science, Daejeon 305-811, Republic of Korea †Department of Physics Education, Daegu University, Gyeongsan 712-714, Republic of Korea ‡School of Natural Science, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea
YL was supported by the Rare Isotope Science Project of Institute for Basic Science funded by Ministry of Science, ICT and Future Planning and National Research Foundation of Korea (NRF) (2013M7A1A1075764). CHH is grateful to the Institute for Basic Science, where part of the work was completed. Work of CHH was supported by Basic Science Research Program through the NRF funded by the Ministry of Education (NRF-2014R1A1A2054096). KK was supported by Basic Science Research Program through the NRF funded by the Ministry of Science, ICT and Future Planning (NRF-2014M1A7A1A03029872). CHL was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (Grant No. NRF-2015R1A2A2A01004238).
© 2015 World Scientific Publishing Company.
- neutron stars
- nuclear matter