NSG Home Page Analytical EOSs of Neutron Star Matter
Fitting programs

These analytical representations are designed for EOSs FPS, SLy4, and APR (APR is available only in the Fortran code, there is no table or C/C++ code).
For "Brussels-Montreal" EOSs BSk19-22 and BSk24-26, follow this link.

For other EOSs, see this collection of links.
Neutron Star Group


The equations of state (EOSs) for neutron-star matter are fitted from mass density rho about 105 g cm-3 to a few times 1015 g cm-3 (baryon number density n about 10-10 fm-3 - a few fm-3). At the low end of this density range, the EOS starts to depend on temperature T. The fits are extended below this density by matching to the dependence P=3.5x1014rho, where pressure P and rho are in CGS units; this is an approximation for the EOS of iron at T = 107 K and rho = (0.1 - 1000) g cm-3.

Arguments of the program:

(for more explanations and definitions see the references).

The subroutine NSEOSFIT(MODE,KEOS,XN,RHO,H1,P,Gamma) returns 4 fitted arguments for 1 input (XN, RHO, or H1). It uses subroutines that realize separate fits: P(rho), n(rho), rho(n), rho(H1). Typical accuracy of the fits is a few percent or better. To achieve the perfect thermodynamic consistency, however, it is advised not to use all the fitted outputs, but to calculate either XN(RHO,P) or RHO(XN,P) using the thermodynamic identities given, e.g., by Eqs.(2),(3) of the basic reference paper (Haensel and Potekhin 2004).

Please communicate us your opinion about this resource or send any suggestions or remarks.

separation line

Tabular EOSs:
short SLy
short FPS
Code to download:
short Fortran
short C/C++

separation line

Page created on April 8, 2004, last updated on September 3, 2017 by Alexander Potekhin.