skip to main content

Title: Magnetic-field Induced Deformation in Hybrid Stars

The effects of strong magnetic fields on the deconfinement phase transition expected to take place in the interior of massive neutron stars are studied in detail for the first time. For hadronic matter, the very general density-dependent relativistic mean field model is employed, while the simple, but effective vector-enhanced bag model is used to study quark matter. Magnetic-field effects are incorporated into the matter equation of state and in the general-relativity solutions, which also satisfy Maxwell’s equations. We find that for large values of magnetic dipole moment, the maximum mass, canonical mass radius, and dimensionless tidal deformability obtained for stars using spherically symmetric Tolman–Oppenheimer–Volkoff (TOV) equations and axisymmetric solutions attained through the LORENE library differ considerably. The deviations depend on the stiffness of the equation of state and on the star mass being analyzed. This points to the fact that, unlike what was assumed previously in the literature, magnetic field thresholds for the approximation of isotropic stars and the acceptable use of TOV equations depend on the matter composition and interactions.

more » « less
Award ID(s):
Author(s) / Creator(s):
; ; ; ; ;
Publisher / Repository:
DOI PREFIX: 10.3847
Date Published:
Journal Name:
The Astrophysical Journal
Medium: X Size: Article No. 52
Article No. 52
Sponsoring Org:
National Science Foundation
More Like this
  1. Cortina-Gil, D (Ed.)

    A comprehensive study is carried out on the impact of strong magnetic fields on the deconfinement phase transition inside massive neutron stars. The matter equation of state and the general relativity solutions, which also fulfill Maxwell’s equations, are modified when taking magnetic-field effects into account. We observe that the maximum mass and canonical-mass radius of stars computed using spherically-symmetric TOV equations and axisymmetric solutions obtained through the LORENE library differ significantly for large values of magnetic dipole moment. The discrepancies depend on the stellar mass being studied, as well as the stiffness of the equation of state. This indicates that the matter composition and interactions determine the magnetic field thresholds for the acceptable approximation of isotropic stars and the appropriate application of TOV equations.

    more » « less
  2. Neutron stars are the endpoint of the life of intermediate mass stars and posses in their cores matter in the most extreme conditions in the universe. Besides their extremes of temperature (found in proto-neutron stars) and densities, typical neutron star' magnetic fields can easily reach trillions of times higher the one of the Sun. Among these stars, about 10% are denominated magnetars which possess even stronger surface magnetic fields of up to 10^15-10^16 G. In this conference proceeding, we present a short review of the history and current literature regarding the modeling of magnetic neutron stars. Our goal is to present the results regarding the introduction of magnetic fields in the equation of state of matter using Relativistic Mean Field models (RMF models) and in the solution of Einstein's equations coupled to the Maxwell's equations in order to generate a consistent calculation of magnetic stars structure. We discuss how equation of state modeling affects mass, radius, deformation, composition and magnetic field distribution in stars and also what are the open questions in this field of research. 
    more » « less

    We model neutron stars as magnetized hybrid stars with an abrupt hadron–quark phase transition in their cores, taking into account current constraints from nuclear experiments and multimessenger observations. We include magnetic field effects considering the Landau level quantization of charged particles and the anomalous magnetic moment of neutral particles. We construct the magnetized hybrid equation of state, and we compute the particle population, the matter magnetization and the transverse and parallel pressure components. We integrate the stable stellar models, considering the dynamical stability for rapid or slow hadron–quark phase conversion. Finally, we calculate the frequencies and damping times of the fundamental and g non-radial oscillation modes. The latter, a key mode to learn about phase transitions in compact objects, is only obtained for stars with slow conversions. For low magnetic fields, we find that one of the objects of the GW170817 binary system might be a hybrid star belonging to the slow extended stability branch. For magnetars, we find that a stronger magnetic field always softens the hadronic equation of state. Besides, only for some parameter combinations a stronger magnetic field implies a higher hybrid star maximum mass. Contrary to previous results, the incorporation of anomalous magnetic moment does not affect the studied astrophysical quantities. We discuss possible imprints of the microphysics of the equation of state that could be tested observationally in the future, and that might help infer the nature of dense matter and hybrid stars.

    more » « less
  4. We investigate the influence of repulsive vector interactions and color superconductivity on the structure of neutron stars using an extended version of the field correlator method (FCM) for the description of quark matter. The hybrid equation of state is constructed using the Maxwell description, which assumes a sharp hadron-quark phase transition. The equation of state of hadronic matter is computed for a density-dependent relativistic lagrangian treated in the mean-field approximation, with parameters given by the SW4L nuclear model. This model described the interactions among baryons in terms of σ, ω, ρ, σ*, and ϕ mesons. Quark matter is assumed to be in either the CFL or the 2SC+s color superconducting phase. The possibility of sequential (hadron-quark, quark-quark) transitions in ultra-dense matter is investigated. Observed data related to massive pulsars, gravitational-wave events, and NICER are used to constrain the parameters of the extended FCM model. The successful equations of state are used to explore the mass-radius relationship, radii, and tidal deformabilities of hybrid stars. A special focus lies on investigating consequences that slow or fast conversions of quark-hadron matter have on the stability and the mass-radius relationship of hybrid stars. We find that if slow conversion should occur, a new branch of stable massive stars would exist whose members have radii that are up to 1.5 km smaller than those of conventional neutron stars of the same mass. Such objects could be possible candidates for the stellar high-mass object of the GW190425 binary system. 
    more » « less
  5. Abstract

    The equation of state (EOS) of dense strongly interacting matter can be probed by astrophysical observations of neutron stars (NS), such as X-ray detections of pulsars or the measurement of the tidal deformability of NSs during the inspiral stage of NS mergers. These observations constrain the EOS at most up to the density of the maximum-mass configuration,nTOV, which is the highest density that can be explored by stable NSs for a given EOS. However, under the right circumstances, binary neutron star (BNS) mergers can create a postmerger remnant that explores densities abovenTOV. In this work, we explore whether the EOS abovenTOVcan be measured from gravitational-wave or electromagnetic observations of the postmerger remnant. We perform a total of 25 numerical-relativity simulations of BNS mergers for a range of EOSs and find no case in which different descriptions of the matter abovenTOVhave a detectable impact on postmerger observables. Hence, we conclude that the EOS abovenTOVcan likely not be probed through BNS merger observations for the current and next generation of detectors.

    more » « less