J/A+A/560/A48 Neutron-star matter unified EoS FORTRAN codes (Potekhin+, 2013)
Analytical representations of unified equations of state for
neutron-star matter.
Potekhin A.Y., Fantina A.F., Chamel N., Pearson J.M., Goriely S.
<Astron. Astrophys. 560, A48 (2013)>
=2013A&A...560A..48P 2013A&A...560A..48P
ADC_Keywords: Models ; Stars, late-type
Keywords: dense matter - equation of state - stars: neutron
Abstract:
An equation of state (EoS) of dense nuclear matter is a prerequisite
for studies of the structure and evolution of compact stars. A unified
EoS should describe the crust and the core of a neutron star using the
same physical model. The Brussels-Montreal group has recently derived
a family of such EoSs based on the nuclear energy-density functional
theory with generalized Skyrme effective forces that have been fitted
with great precision to essentially all the available mass data. At
the same time, these forces were constrained to reproduce microscopic
calculations of homogeneous neutron matter based on realistic two- and
three-nucleon forces.
We represent basic physical characteristics of the latest
Brussels-Montreal EoS models by analytical expressions to facilitate
their inclusion in astrophysical simulations.
We consider three EoS models, which significantly differ by stiffness:
BSk19, BSk20, and BSk21. For each of them we constructed two versions
of the EoS parametrization. In the first version, pressure P and
gravitational mass density ρ are given as functions of the baryon
number density nb. In the second version, P, ρ, and nb are given
as functions of pseudo-enthalpy, which is useful for two-dimensional
calculations of stationary rotating configurations of neutron stars.
In addition to the EoS, we derived analytical expressions for several
related quantities that are required in neutron-star simulations:
number fractions of electrons and muons in the stellar core, nucleon
numbers per nucleus in the inner crust, and equivalent radii and shape
parameters of the nuclei in the inner crust.
We obtain analytical representations for the basic characteristics of
the models of cold dense matter, which are most important for studies
of neutron stars. We demonstrate the usability of our results by
applying them to calculations of neutron-star mass-radius relations,
maximum and minimum masses, thresholds of direct Urca processes, and
the electron conductivity in the neutron-star crust.
Description:
The FORTRAN codes implement the formulae for the unified EoSs of
neutron-star matter BSk19, BSk20, and BSk21, supplemented with codes
for masses and radii of static neutron stars, number fractions of
particles, nuclear size and shape parameters, and effective masses of
nucleons.
Detailed descriptions of all subroutines are given by comment lines in
the files
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
bskfit.f 72 338 Set of FORTRAN subroutines for the EoS, number
fractions of particles, and shape and size
parameters of nuclei
bskeos.f 72 102 Auxiliary code for demonstration purposes;
to be linked with bskfit.f
tovbsk.f 72 169 Neutron-star masses and radii by integration
of the TOV equation with the use of bskfit.f
meff.f 72 81 FORTRAN code for the effective nucleon masses
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Description of file:
bskfit.f :
------------------------------------------------------------------------------
Name of subroutine Description
------------------------------------------------------------------------------
BSKfit Returns pressure and its log.derivative over density
at a given mass density.
BSKfitH Returns mass density as function of exp(H)-1,
where H is pseudo-enthalpy.
BSkRofN Returns mass density as function of baryon number density.
BSkNofR Returns baryon number density as function of mass density.
FRACORE Returns fractions of electrons and muons as functions of
number density in the stellar core.
INCRUST At a given baryon number density, returns:
- the number of bound electrons in a nucleus;
- the total number of nucleons per a nucleus;
- the total number of protons per a nucleus;
- the number of clusterized protons in a nucleus;
- four nuclear shape parameters;
- heights of the bumps of proton and neutron densities
near the center of a Wigner-Seitz cell;
- the ratios of the effective proton and neutron radii of
these bumps, respectively, to the cell radius.
------------------------------------------------------------------------------
bskeos.f
------------------------------------------------------------------------------
Name of subroutine Description
------------------------------------------------------------------------------
MAIN Allows one to choose the EoS (BSk19, BSk20, or BSk21)
and the input (mass density, number density, or
pseudo-enthalpy); returns the pressure, adiabatic
exponent, and mass density, number density, or
pseudo-enthalpy depending on the chosen input.
BSKEOS Organizes calls of relevant subroutines from bskfit.f
depending on the chosen input/output mode.
------------------------------------------------------------------------------
tovbskfit.f
------------------------------------------------------------------------------
Name of subroutine Description
------------------------------------------------------------------------------
MAIN Allows one to choose the EoS (BSk19, BSk20, or BSk21) and
the central stellar mass density; returns the stellar
mass and radius.
TOVINT For a given EoS choice, given central mass density, and
given accuracy level, calculates the stellar mass and
radius by solving the TOV equation by the Runge-Kutta
algorithm.
SUBRHS Implements one substep in the Runge-Kutta integration.
------------------------------------------------------------------------------
meff.f:
------------------------------------------------------------------------------
Name of subroutine Description
------------------------------------------------------------------------------
MAIN For a given EoS (BSk19, BSk20, or BSk21) and given baryon
number density, calculates the proton number fraction by
calling FRACORE from bskfit.f and then calls EFFMASS
to calculates the effective proton and neutron masses.
EFFMASS For given EoS, baryon number density, and proton number
fraction, calculates the effective proton and neutron
masses, following the algorithm of Chamel, Goriely, &
Pearson [Phys. Rev. C 80, 065804 (2009)] with the
parameters from Goriely, Chamel, & Pearson [Phys. Rev. C
82, 035804 (2010)].
------------------------------------------------------------------------------
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Acknowledgements:
Alexander Y. Potekhin, palex(at)astro.ioffe.ru
(End) Patricia Vannier [CDS] 30-Sep-2013