Uniformly rotating neutron stars in the global and local charge neutrality cases

Belvedere, Riccardo; Boshkayev, Kuantay; Rueda, J. A.; Ruffini, Remo

doi:10.1016/j.nuclphysa.2013.11.001

Cited by 53 publications

(73 citation statements)

References 33 publications

(73 reference statements)

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“…For the rotational periods as the ones observed in SGR/AXPs (P ∼ 2-12 s), the structure of the rotating NS can be accurately described by small rotation perturbations from the spherically symmetric configuration (see, e.g., Belvedere et al 2014Belvedere et al , 2015, using the Hartle's formalism (Hartle 1967 charge neutrality are shown in Fig. 2.…”

Section: Mass-radius Relation and Moment Of Inertiamentioning

confidence: 85%

“…mass and radius, we need to construct the equilibrium configurations of a uniformly rotating NS in the range of the observed periods. We have shown in Rotondo et al (2011);Rueda et al (2011);Belvedere et al (2012Belvedere et al ( , 2014 that, in the case of both static and rotating NSs, the Tolman-Oppenheimer-Volkoff (TOV) system of equations (Oppenheimer & Volkoff 1939;Tolman 1939) is superseded by the Einstein-Maxwell system of equations coupled to the general relativistic Thomas-Fermi equations of equilibrium, giving rise to what we have called the Einstein-Maxwell-Thomas-Fermi (EMTF) equations. In the TOV-like approach, the condition of local charge neutrality is applied to each point of the configuration, while in the EMTF equations the condition of global charge neutrality is imposed.…”

Section: Neutron Star Structurementioning

confidence: 99%

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The rotation-powered nature of some soft gamma-ray repeaters and anomalous X-ray pulsars

Coelho

Cáceres

Lima

et al. 2017

A&A

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Context. Soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are slow rotating isolated pulsars whose energy reservoir is still matter of debate. Adopting neutron star (NS) fiducial parameters; mass M = 1.4M , radius R = 10 km, and moment of inertia, I = 10 45 g cm 2 , the rotational energy loss,Ė rot , is lower than the observed luminosity (dominated by the X-rays) L X for many of the sources. Aims. We investigate the possibility that some members of this family could be canonical rotation-powered pulsars using realistic NS structure parameters instead of fiducial values. Methods. We compute the NS mass, radius, moment of inertia and angular momentum from numerical integration of the axisymmetric general relativistic equations of equilibrium. We then compute the entire range of allowed values of the rotational energy loss,Ė rot , for the observed values of rotation period P and spin-down rateṖ. We also estimate the surface magnetic field using a general relativistic model of a rotating magnetic dipole. Results. We show that realistic NS parameters lowers the estimated value of the magnetic field and radiation efficiency, L X /Ė rot , with respect to estimates based on fiducial NS parameters. We show that nine SGRs/AXPs can be described as canonical pulsars driven by the NS rotational energy, for L X computed in the soft (2-10 keV) X-ray band. We compute the range of NS masses for which L X /Ė rot < 1. We discuss the observed hard X-ray emission in three sources of the group of nine potentially rotation-powered NSs. This additional hard X-ray component dominates over the soft one leading to L X /Ė rot > 1 in two of them. Conclusions. We show that 9 SGRs/AXPs can be rotation-powered NSs if we analyze their X-ray luminosity in the soft 2-10 keV band. Interestingly, four of them show radio emission and six have been associated with supernova remnants (including Swift J1834.9-0846 the first SGR observed with a surrounding wind nebula). These observations give additional support to our results of a natural explanation of these sources in terms of ordinary pulsars. Including the hard X-ray emission observed in three sources of the group of potential rotation-powered NSs, this number of sources with L X /Ė rot < 1 becomes seven. It remains open to verification 1) the accuracy of the estimated distances and 2) the possible contribution of the associated supernova remnants to the hard X-ray emission.

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Section: Mass-radius Relation and Moment Of Inertiamentioning

confidence: 85%

Section: Neutron Star Structurementioning

confidence: 99%

The rotation-powered nature of some soft gamma-ray repeaters and anomalous X-ray pulsars

Coelho

Cáceres

Lima

et al. 2017

A&A

View full text Add to dashboard Cite

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“…The extension of the above formulation to the case of uniform rotation has been recently achieved in (Belvedere et al 2014) within the Hartle formalism (Hartle 1967). It is worth TABLE 1 Properties of the high-magnetic field pulsars obtained assuming fiducial neutron star parameters, R = 10 km and I = 10 45 g cm 2 , respectively, and using Eq.…”

Section: Neutron Star Structurementioning

confidence: 99%

“…to underline that the influence of the induced magnetic field owing to the rotation of the charged core of the neutron star in the globally neutral case is negligible as we will show in subsection 2.1. From the integration of the equations of equilibrium, we computed in Belvedere et al (2014), for different central densities ρ c and circular angular velocities Ω, the mass M, polar R p and equatorial R eq radii, angular momentum J, eccentricity ǫ, moment of inertia I, as well as quadrupole moment Q of the configurations. The angular momentum J of the star is given by…”

Section: Neutron Star Structurementioning

confidence: 99%

“…For the latter configurations we use our recent formulation of the neutron star theory for both static and uniform rotation, following our previous works (Belvedere et al 2012(Belvedere et al , 2014. These new set of equations, which we called Einstein-Maxwell-Thomas-Fermi equations, accounts for the weak, strong, gravitational and electromagnetic interactions within the framework of general relativity and relativistic nuclear mean-field theory.…”

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confidence: 99%

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On the Magnetic Field of Pulsars With Realistic Neutron Star Configurations

Belvedere

Rueda

Ruffini

2015

ApJ

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We have recently developed a neutron star model fulfilling global and not local charge neutrality, both in the static and in the uniformly rotating cases. The model is described by the coupled Einstein-Maxwell-ThomasFermi (EMTF) equations, in which all fundamental interactions are accounted for in the framework of general relativity and relativistic mean field theory. Uniform rotation is introduced following the Hartle's formalism. We show that the use of realistic parameters of rotating neutron stars obtained from numerical integration of the self-consistent axisymmetric general relativistic equations of equilibrium leads to values of the magnetic field and radiation efficiency of pulsars very different from estimates based on fiducial parameters assuming a neutron star mass, M = 1.4 M ⊙ , radius R = 10 km, and moment of inertia, I = 10 45 g cm 2 . In addition, we compare and contrast the magnetic field inferred from the traditional Newtonian rotating magnetic dipole model with respect to the one obtained from its general relativistic analog which takes into due account the effect of the finite size of the source. We apply these considerations to the specific high-magnetic field pulsars class and show that, indeed, all these sources can be described as canonical pulsars driven by the rotational energy of the neutron star, and with magnetic fields lower than the quantum critical field for any value of the neutron star mass.

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Gravity-darkening exponents for neutron and non-relativistic stars

Claret

2015

A&A

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Context. Rotation affects various aspects of the stellar structure and evolution. For example, it distorts the star and causes the energy flow to be dependent on the local gravity (von Zeipel effect). Recent advances in the semi-empirical derivation of the gravity-darkening exponents in eclipsing binaries and very fast rotators require new theoretical calculations so that the results can be compared with these observations. Aims. Using an analytical alternative method, we studied how the temperature is distributed over distorted neutron star (NS) surfaces through the gravity-darkening exponent (GDE). We also extended these investigations to non-relativistic stars.Methods. The envelopes of NS, whose properties are necessary to derive the GDE, were computed using routines of the code mesa. The non-relativistic stellar models were computed following the code granada.Results. We use a perturbation theory to derive an equation for the GDE for neutron and non-relativistic stars as a function of the rotation law, of the colatitude, and of the logarithmic derivatives of the opacity. Significant deviations from the von Zeipel's theorem were found for differentially rotating NS as well as for non-relativistic stars. This equation is also capable of predicting the transition zone in the GDE around log T eff = 3.9 for non-relativistic stars, in good agreement with observational data. We use this equation to explore the effects of differential rotation to explain the anomalous values of semi-empirical GDE found in some early-type eclipsing binaries. We also analysed the role of convection and of the change of the main thermonuclear energy source in the GDE calculations for late-type stars.

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Uniformly rotating neutron stars in the global and local charge neutrality cases

Cited by 53 publications

References 33 publications

The rotation-powered nature of some soft gamma-ray repeaters and anomalous X-ray pulsars

The rotation-powered nature of some soft gamma-ray repeaters and anomalous X-ray pulsars

On the Magnetic Field of Pulsars With Realistic Neutron Star Configurations

Gravity-darkening exponents for neutron and non-relativistic stars

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