Interface

There are two classes to represent neutron star sequences. The basic one is star_seq, which represents sequences with an arbitrary range of central density. The other is star_branch, which represents a stable branch where properties can be obtained also as function of gravitational mass. The class star_branch derives from star_seq and can thus be used as a sequence as well. Both classes store the units they use, which can be freely specified during creation but are assumed to be geometric. Each object provides a method units_to_SI() to query the units.

To compute a sequence of TOV stars, use the function make_tov_seq(), specifying the EOS, the desired accuracy (see TOV solver), the range of central pseudo-enthalpy, and the number of sample points. The units are taken from the EOS.

To compute a stable branch for TOV stars, use the function make_tov_branch_stable(). To select the correct branch in case there are several, one can provide one central pseudo-enthalpy within the desired branch. The default value should work for almost any remotely realistic NS EOS. One can also specify a minimum mass that has to be covered by the sequence. The units for the sequence are copied from the EOS.

To create a star sequence directly from data points, use make_star_seq(), specifying vectors for the NS properties. Currently, those need to be equally spaced in central pseudo enthalpy. For the latter, only the range needs to be given, not a vector. Further, one needs to specify the unit system to which the provided data refers, which is assumed geometric.

The following example demonstrates basic use of stable TOV branches.

#include "reprimand/unitconv.h"
#include "reprimand/eos_barotropic.h"
#include "reprimand/eos_barotr_file.h"
#include "reprimand/star_sequence.h"
#include "reprimand/star_seq_file.h"


using namespace EOS_Toolkit;

int main() {
    // Choose geometric units to work in
    auto u = units::geom_solar();

    //Load EOS from file
    auto eos = load_eos_barotr("example.eos.h5", u);
    
    // Specification for desired accuracy: using defaults
    const auto acc = star_acc_simple();
    
    // Create stable TOV branch
    auto seq = make_tov_branch_stable(eos, acc);
    
    // Save branch to file 
    save_star_branch("example.tovseq.h5", seq);
    
    // Compute tidal deformability at 90% of maximum mass
    
    double mass = 0.9 * seq.grav_mass_maximum();
    
    double lambda09 
      = seq.lambda_tidal_from_grav_mass(mass);
}

Tip

NS sequences represented by star_sequence or star_branch can be copied cheaply, and one does not need to worry about memory management. Internally, the data points for interpolation are managed by reference counted shared pointers. Using sequences or branches is thread-save.