Neutron Star Structure and the Equation of State

By J. Lattimer, M. Prakash. 2000

1,351 citations recorded by the source corpus.

The structure of neutron stars is considered from theoretical and observational perspectives. We demonstrate an important aspect of neutron star structure: the neutron star radius is primarily determined by the behavior of the pressure of matter in the vicinity of nuclear matter equilibrium density. In the event that extreme softening does not occur at these densities, the radius is virtually independent of the mass and is determined by the magnitude of the pressure. For equations of state with extreme softening or those that are self-bound, the radius is more sensitive to the mass. Our results show that in the absence of extreme softening, a measurement of the radius of a neutron star more accurate than about 1 km will usefully constrain the equation of state. We also show that the pressure near nuclear matter density is primarily a function of the density dependence of the nuclear symmetry energy, while the nuclear incompressibility and skewness parameters play secondary roles. In addition, we show that the moment of inertia and the binding energy of neutron stars, for a large class of equations of state, are nearly universal functions of the star's compactness. These features can be understood by considering two analytic, yet realistic, solutions of Einstein's equations, by, respectively, Buchdahl and Tolman. We deduce useful approximations for the fraction of the moment of inertia residing in the crust, which is a function of the stellar compactness and, in addition, the pressure at the core-crust interface.

Subfields: Astronomy and Astrophysics, Geophysics

View Paper: https://www.semanticscholar.org/paper/e73daf918e52dd1afaa185bdf6539f90045f3b98

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Citations in the corpus

Moments of inertia for neutron and strange stars: Limits derived for the Crab pulsar (2002, result): “After studying various types of correlations between I, M and R, we found, in accordance with Lattimer & Prakash (2001), that it is the ratio I/MR2 which has the most Fig.”
Toward a Mass and Radius Determination of the Nearby Isolated Neutron Star RX J185635–3754 (2001, background): “The EOSs in this figure are labelled following the convention of Lattimer & Prakash (2001), and include cases with baryonic compositions (MS0, MS1, PAL6, GM3, AP4) together with one with a kaoncondensed core (GS1), all indicated by solid curves.”
A unified equation of state of dense matter and neutron star structure (2001, background): “The reasons for such a weak dependence of R on M have been explained by Lattimer & Prakash (2001).”
NEUTRON STAR MASSES AND RADII FROM QUIESCENT LOW-MASS X-RAY BINARIES (2013, background): “Even EOSs without strong phase transitions, and with maximum masses satisfying observational values, predict radius variations ∆R > 1 km for 0.5M⊙ < M < 1.8M⊙ and ∆R > 2 − 3 km for masses near the maximum mass, especially for EOSs with relatively large radii (see, e.g., Lattimer & Prakash (2001)).”
Maximum mass, moment of inertia and compactness of relativistic stars (2016, methodology): “Lattimer & Prakash (2001) and Lattimer & Schutz (2005) found that fitting functions of the type (19) were valid for a wide range of EOS except the ones which exhibited extreme softening.”
A Hydrogen Atmosphere Spectral Model Applied to the Neutron Star X7 in the Globular Cluster 47 Tucanae (2005, methodology): “The MS1 model is an example of models consistent with a larger radius at 1.4M⊙ (see Lattimer & Prakash 2001), some of which include condensation of kaons, hyperons, muons or free quarks in the core.”
The QCD equation of state in background magnetic fields (2014, background): “Besides its role in heavy-ion physics, the EoS affects the mass-radius relation of neutron stars [5] and enters cosmological models of the early universe, with implications, for example, for dark matter candidates [6].”
Discovery of Fast X-Ray Oscillations during the 1998 Giant Flare from SGR 1900+14 (2005, methodology): “We model four of the EOS discussed in Lattimer & Prakash (2001); in order of increasing stiffness they are WFF1, AP4, AP3 and MS0.”