THE EQUATION OF STATE FROM OBSERVED MASSES AND RADII OF NEUTRON STARS

By A. Steiner, J. Lattimer, E. Brown. 2010

629 citations recorded by the source corpus.

We determine an empirical dense matter equation of state (EOS) from a heterogeneous data set of six neutron stars: three Type-I X-ray bursters with photospheric radius expansion, studied by Özel et al., and three transient low-mass X-ray binaries. We critically assess the mass and radius determinations from the X-ray burst sources and show explicitly how systematic uncertainties, such as the photospheric radius at touchdown, affect the most probable masses and radii. We introduce a parameterized EOS and use a Markov chain Monte Carlo algorithm within a Bayesian framework to determine nuclear parameters such as the incompressibility and the density dependence of the bulk symmetry energy. Using this framework we show, for the first time, that these parameters, predicted solely on the basis of astrophysical observations, all lie in ranges expected from nuclear systematics and laboratory experiments. We find significant constraints on the mass–radius relation for neutron stars, and hence on the pressure–density relation of dense matter. The predicted symmetry energy and the EOS near the saturation density are soft, resulting in relatively small neutron star radii around 11–12 km for M = 1.4 M☉. The predicted EOS stiffens at higher densities, however, and our preferred model for X-ray bursts suggests that the neutron star maximum mass is relatively large, 1.9–2.2 M☉. Our results imply that several commonly used equations of state are inconsistent with observations.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/b93f7b4f4bbfbb7a5dd275b44fa28f4c6ddf45ae

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In Astronomy and Astrophysics

Citations in the corpus

A NICER View of PSR J0030+0451: Implications for the Dense Matter Equation of State (2019, background): “Steiner et al. (2010, 2013, 2018) and Lattimer & Steiner (2014) considered a larger range of parameterized EoS models to infer dense matter parameters including those associated with the nuclear symmetry energy and the mass–radius bands.”
Combined Constraints on the Equation of State of Dense Neutron-rich Matter from Terrestrial Nuclear Experiments and Observations of Neutron Stars (2018, background): “(Danielewicz et al. 2002; Shlomo et al. 2006; Chen et al. 2009; Steiner et al. 2010; Piekarewicz 2010; Khan et al. 2012; Dutra et al. 2012, 2014; Li & Han 2013; Colò et al. 2014; Cai & Chen 2014; Zhang et al. 2017).”
Generic conditions for stable hybrid stars (2013, background): “[26] finds the surface to volume symmetry energy ratio Ss/Sv ≈ 1.”
Constraints on perturbative f(R) gravity via neutron stars (2010, background): “In fact for such large values of |α| we can not obtain M-R relations For a critic of these constraints see [39].”
CONSTRAINING THE SYMMETRY PARAMETERS OF THE NUCLEAR INTERACTION (2012, methodology): “The average value is the same as determined by Steiner et al. (2010), but the range is broader due to the consideration of a greater variety of scenarios in an attempt to capture systematic uncertainties in models.”
Neutron star mass and radius measurements from atmospheric model fits to X-ray burst cooling tail spectra (2017, neutral): “…for example, if the model is applied to data that it does not describe, such as data from soft-state bursts where the behaviour of the cooling tail might not be totally determined by the NS surface alone (see Steiner et al. 2010; Poutanen et al. 2014; Kajava et al. 2014; Nättilä et al. 2016).”
CORE-COLLAPSE SUPERNOVA EQUATIONS OF STATE BASED ON NEUTRON STAR OBSERVATIONS (2012, methodology): “The gray region gives the 1 σ confidence limits on the EOS from Steiner et al. (2010).”
A new quark-hadron hybrid equation of state for astrophysics - I. High-mass twin compact stars (2014, methodology): “We note that in addition to the size of the emitting region, the main issue of the radius analyses using X-ray burst sources such as Steiner et al. (2010) and Steiner et al. (2013), is the question of the atmosphere composition.”
SYSTEMATICS OF DYNAMICAL MASS EJECTION, NUCLEOSYNTHESIS, AND RADIOACTIVELY POWERED ELECTROMAGNETIC SIGNALS FROM NEUTRON-STAR MERGERS (2013, background): “…mass-radius-relations) which are compatible with present observational constraints (e.g., the 1.97M⊙ NS discovery of Demorest et al. (2010), and more recently 2.01M⊙ by Antoniadis et al. (2013)) and theoretical understanding (Lattimer & Prakash 2010, 2007; Steiner et al. 2010; Hebeler et al. 2010).”