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Stringent constraints on neutron-star radii from multimessenger observations and nuclear theory

Abstract

The properties of neutron stars are determined by the nature of the matter that they contain. These properties can be constrained by measurements of the star’s size. We obtain stringent constraints on neutron-star radii by combining multimessenger observations of the binary neutron-star merger GW170817 with nuclear theory that best accounts for density-dependent uncertainties in the equation of state. We construct equations of state constrained by chiral effective field theory and marginalize over these using the gravitational-wave observations. Combining this with the electromagnetic observations of the merger remnant that imply the presence of a short-lived hypermassive neutron star, we find that the radius of a 1.4 M neutron star is \({R}_{1.4{M}_{\odot }}={11.0}_{-0.6}^{+0.9}\ {\rm{km}}\) (90% credible interval). Using this constraint, we show that neutron stars are unlikely to be disrupted in neutron star–black hole mergers; subsequently, such events will not produce observable electromagnetic emission.

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Fig. 1: Comparison of the estimated \({R}_{1.4{M}_{\odot }}\) at different stages of our analysis.
Fig. 2: Mass–radius relation for the two equation-of-state sets.
Fig. 3: Implications for electromagnetic counterparts to neutron star–black hole mergers.

Data availability

All data are available in the manuscript or the Supplementary Information. Full posterior data samples are available at https://github.com/sugwg/gw170817-eft-eos. The gravitational-wave data used in this work were obtained from the Gravitational Wave Open Science Center (GWOSC) at https://www.gw-openscience.org.

Code availability

All software used in this analysis is open source and available from https://github.com/gwastro/pycbc.

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Acknowledgements

We thank B. Allen, W. Kastaun, J. Lattimer and B. Metzger for valuable discussions. This work was supported by US National Science Foundation grants PHY-1430152 to the JINA Center for the Evolution of the Elements (S.R.), PHY-1707954 (D.A.B. and S.D.); US Department of Energy grant DE-FG02-00ER41132 (S.R.); NASA Hubble Fellowship grant number HST-HF2-51412.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555 (B.M.); and the US Department of Energy, Office of Science, Office of Nuclear Physics, under contract DE-AC52-06NA25396, the Los Alamos National Laboratory (LANL) LDRD programme and the NUCLEI SciDAC programme (I.T.). D.A.B., S.D. and B.M. thank the Kavli Institute for Theoretical Physics (KITP) where portions of this work were completed. KITP is supported in part by the National Science Foundation under grant number NSF PHY-1748958. Computational resources have been provided by Los Alamos Open Supercomputing via the Institutional Computing (IC) programme, by the National Energy Research Scientific Computing Center (NERSC), by the Jülich Supercomputing Center, by the ATLAS Cluster at the Albert Einstein Institute in Hannover, and by Syracuse University. GWOSC is a service of LIGO Laboratory, the LIGO Scientific Collaboration and the Virgo Collaboration. LIGO is funded by the National Science Foundation. Virgo is funded by the French Centre National de Recherche Scientifique (CNRS), the Italian Istituto Nazionale della Fisica Nucleare (INFN) and the Dutch Nikhef, with contributions by Polish and Hungarian institutes. B.M. is a NASA Einstein Fellow.

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Conceptualization: D.A.B., C.D.C., B.K., B.M., S.R., I.T. Data curation: D.A.B., C.D.C., S.D., I.T. Formal analysis, C.D.C., S.M.B., I.T., S.D. Funding acquisition: D.A.B., B.K., B.M., S.R., I.T. Methodology: D.A.B., C.D.C., S.D., B.K., B.M., S.R., I.T. Project administration: D.A.B., B.K., S.R., I.T. Resources: D.A.B., B.K., I.T. Software: D.A.B., S.M.B., C.D.C., S.D., S.K., B.M., I.T. Supervision: D.A.B., B.K., S.R. Validation: D.A.B., S.M.B., C.D.C., S.D., I.T. Visualization: S.M.B., C.D.C., B.M. Writing—original draft: D.A.B., S.M.B., C.D.C., I.T. Writing—review and editing: D,.A.B., S.M.B., C.D.C., S.D., B.K., B.M., S.R., I.T.

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Correspondence to Collin D. Capano.

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Capano, C.D., Tews, I., Brown, S.M. et al. Stringent constraints on neutron-star radii from multimessenger observations and nuclear theory. Nat Astron 4, 625–632 (2020). https://doi.org/10.1038/s41550-020-1014-6

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