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Nonparametric constraints on neutron star matter with existing and upcoming gravitational wave and pulsar observations

Landry, Philippe and Essick, Reed and Chatziioannou, Katerina (2020) Nonparametric constraints on neutron star matter with existing and upcoming gravitational wave and pulsar observations. Physical Review D, 101 (12). Art. No. 123007. ISSN 2470-0010.

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Observations of neutron stars, whether in binaries or in isolation, provide information about the internal structure of the most extreme material objects in the Universe. In this work, we combine information from recent observations to place joint constraints on the properties of neutron star matter. We use (i) lower limits on the maximum mass of neutron stars obtained through radio observations of heavy pulsars, (ii) constraints on tidal properties inferred through the gravitational waves neutron star binaries emit as they coalesce, and (iii) information about neutron stars’ masses and radii obtained through X-ray emission from surface hot spots. In order to combine information from such distinct messengers while avoiding the kind of modeling systematics intrinsic to parametric inference schemes, we employ a nonparametric representation of the neutron-star equation of state based on Gaussian processes conditioned on nuclear theory models. We find that existing astronomical observations imply R_(1.4) = 12.32^(+1.09)_(−1.47)  km for the radius of a 1.4  M⊙ neutron star and p(2ρ_(nuc)) = 3.8^(+2.7)_(−2.9) × 10³⁴  dyn/cm² for the pressure at twice nuclear saturation density at the 90% credible level. The upper bounds are driven by the gravitational wave observations, while X-ray and heavy pulsar observations drive the lower bounds. Additionally, we compute expected constraints from potential future astronomical observations and find that they can jointly determine R_(1.4) to O(1)  km and p(2ρ_(nuc)) to 80% relative uncertainty in the next five years.

Item Type:Article
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URLURL TypeDescription Paper
Landry, Philippe0000-0002-8457-1964
Chatziioannou, Katerina0000-0002-5833-413X
Additional Information:© 2020 American Physical Society. Received 19 March 2020; accepted 18 May 2020; published 4 June 2020. The authors thank Cole Miller, Jocelyn Read, Andrew Steiner, and Sukanta Bose for helpful suggestions about this work. P. L. is supported by National Science Foundation Grant No. PHY-1836734 and by a gift from the Dan Black Family Trust to the Gravitational-Wave Physics & Astronomy Center. R. E. is supported at the University of Chicago by the Kavli Institute for Cosmological Physics through an endowment from the Kavli Foundation and its founder Fred Kavli. The Flatiron Institute is supported by the Simons Foundation. The authors are grateful for computational resources provided by the LIGO Laboratory and supported by National Science Foundation Grants No. PHY-0757058 and No. PHY-0823459. This analysis was made possible by the numpy [147] and matplotlib [148] software packages.
Funding AgencyGrant Number
Dan Black Family TrustUNSPECIFIED
University of ChicagoUNSPECIFIED
Kavli FoundationUNSPECIFIED
Simons FoundationUNSPECIFIED
Issue or Number:12
Record Number:CaltechAUTHORS:20200803-083736080
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104694
Deposited By: Tony Diaz
Deposited On:03 Aug 2020 15:47
Last Modified:03 Aug 2020 15:47

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