Strongly magnetized strange baryonic matter in neutron star

We investigate the strongly magnetized strange baryonic matter in a relativistic mean-…eld theory. We …rst take into account the hidden strange mesons and the …eld-dependent meson-baryon coupling constants. In low-density region the strongly magnetized neutron star (NS) matter is nearly iso-symmetric. The equation of state (EOS) therefore becomes softer than that of the normal NS matter. Because the magnetic …eld increases the threshold densities of and , the EOS becomes sti¤er in high-density region. However, the magnetic …eld has little e¤ect on the e¤ective masses of and . Taking into account the anomalous magnetic moments (AMMs) of baryons, the EOS becomes much sti¤er although the threshold densities of +, 0 and 0 decrease largely. The density dependence of the e¤ective mass of precisely re‡ects the EOS while the e¤ective masses of and are strongly in‡uenced by the AMMs of nucleons through the scalar mean-…eld. In recent astronomy and astrophysics there are great interests in the magnetars [1-5]. They are the neutron stars (NSs) that involve stronger magnetic …elds 10G < B < 10G than the critical strength BC(e) = me= (2 B) = 4:414 10G for electrons. Although the …eld is still much weaker than the critical strength BC(N) = MN= (2 N) = 1:488 10G for nucleons, the magnetar has stimulated the investigations [6-11] of extremely magnetized nuclear matter in a core of NS within the modern relativistic mean-…eld (RMF) theory [12]. In this respect, it is noted that in the RMF models the mass of a nucleon in dense medium is largely reduced from its free value, and so the magnetic …eld B < BC(N) is able to have signi…cant e¤ect on NS matter. It is generally expected [13,14] that the hyperons play important roles in the inner cores of NSs. Most of the preceding works [6-11] for strongly magnetized NS matter however considered only nucleons as baryons. Only the paper [15] took into account hyperons within the so-called nonlinear Walecka (NLW) model [16]. On the other hand, it has been recently shown [17,18] that the NLWmodel is not useful in studying dense NS matter while the truly nonlinear RMF models, which should have …eld-dependent mesonbaryon coupling constants, are promising. The most familiar RMF model embodying the true non-linearity is the Zimanyi-Moszkowski (ZM) model [19]1. It has a renormalized 1Although Ref. [15] also calculated using the naive extension of the ZM model to hyperons, the results were not shown in …gures.