Dense stellar matter with trapped neutrinos under strong magnetic fields

Abstract

We investigate the effects of strong magnetic fields on the equation of state of dense stellar neutrino-free and neutrino-trapped matter. Relativistic nuclear models both with constant couplings (NLW) and with density dependent parameters (DDRH) and including hyperons are considered . It is shown that at low densities neutrinos are suppressed in the presence of the magnetic field. The magnetic field reduces the strangeness fraction of neutrino-free matter and increases the strangeness fraction of neutrino-trapped matter. The mass-radius relation of stars described by these equations of state are determined. The magnetic field makes the overall equation of state stiffer and the stronger the field the larger the mass of maximum mass star and the smaller the baryon density at the center of the star. As a consequence in the presence of strong magnetic fields the possibility that a protoneutron star evolves to a blackhole is smaller.

Warm and dense stellar matter under strong magnetic fields

“…The magnetic field lowers the strangeness fraction for neutrino free matter and almost does not affect the strangeness fraction for neutrino trapped matter. This effect was already discussed in [32] and is due to the fact that with the presence of neutrinos the neutron chemical potential does not suffer such a large reduction as in neutrino free matter. The top panel of Fig.…”

“…As discussed in [16,32] the behaviour observed among the different hyperons is mainly due to a decrease of the neutron chemical potential, due to a smaller isospin asymmetry, and a decrease of the electron chemical potential due to Landau quantization. In fact, at low densities, the fraction of proton and leptons are significantly affected by the magnetic field.…”

“…Previously, it was shown that there is a strong neutrino suppression at low densities for finite magnetic fields [32]. For a finite entropy also at high densities a strong magnetic field gives rise to a decrease of the neutrino fraction, due to the larger proton fraction that favors a larger electron fraction.…”

Magnetic susceptibility and magnetization properties of asymmetric nuclear matter in a strong magnetic field

“…The density dependence of the energy of the system and its pressure, as well as its compressibility, is analyzed for different proton fractions and magnetic fields. We will not consider β-equilibrium matter in most of the results shown, but will consider a wide range of nuclear matter asymmetries of interest for stellar matter, in particular, to the study of the inner crust, where a pasta phase is expected [49], to the study of matter with trapped neutrinos where large proton fractions are expected, which may be as large as 0.4 in the presence of a magnetic field [50], and to the study of neutrino free matter in β-equilibrium where the proton fraction will increase above 0.1 at subsaturation densities for a sufficiently strong magnetic field [51]. Therefore, besides symmetric nuclear matter and neutron matter, we choose two representative proton fractions, namely Y p = 0.1 for cold β-equilibrium matter and Y p = 0.3 for warm protoneutron star matter with a fraction of 0.4 trapped leptons.…”

Extreme neutron stars from Extended Theories of Gravity

“…Realistic EoS with hyperons and quarks in presence of strong magnetic field are considered in [22][23][24][25]. The maximal mass of neutron star can exceed, in these cases, 3M ⊙ for B c ∼ 3.3 × 10 18 G. Therefore it seems that the existence of neutron stars with masses exceeding considerably two solar mass (without strong magnetic field) is impossible in the framework of General Relativity (GR).…”