We combine equation of state of dense matter up to twice nuclear saturation density (nsat =
0.16 fm−3
) obtained using chiral effective field theory (χEFT), and recent observations of neutron
stars to gain insights about the high-density matter encountered in their cores. A key element in
our study is the recent Bayesian analysis of correlated EFT truncation errors based on order-byorder calculations up to next-to-next-to-next-to-leading order in the χEFT expansion. We refine the
bounds on the maximum mass imposed by causality at high densities, and provide stringent limits
on the maximum and minimum radii of ∼ 1.4 M and ∼ 2.0 M stars. Including χEFT predictions
from nsat to 2 nsat reduces the permitted ranges of the radius of a 1.4 M star, R1.4, by ∼ 3.5 km.
If observations indicate R1.4 < 11.2 km, our study implies that either the squared speed of sound
c
2
s > 1/2 for densities above 2 nsat, or that χEFT breaks down below 2 nsat. We also comment
on the nature of the secondary compact object in GW190814 with mass ' 2.6 M , and discuss
the implications of massive neutron stars > 2.1 M (2.6 M ) in future radio and gravitational-wave
searches. Some form of strongly interacting matter with c
2
s > 0.35 (0.55) must be realized in the
cores of such massive neutron stars. In the absence of phase transitions below 2 nsat, the small tidal
deformability inferred from GW170817 lends support for the relatively small pressure predicted by
χEFT for the baryon density nB in the range 1−2 nsat. Together they imply that the rapid stiffening
required to support a high maximum mass should occur only when nB & 1.5 − 1.8 nsat.
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Neutron Star Radii, Deformabilities, and Moments of Inertia from Experimental and Ab Initio Theory Constraints of the 208Pb Neutron Skin Thickness
Recent experimental and ab initio theory investigations of the 208Pb neutron skin thickness have the potential to inform the neutron star equation of state. In particular, the strong correlation between the 208Pb neutron skin thickness and the pressure of neutron matter at normal nuclear densities leads to modified predictions for the radii, tidal deformabilities, and moments of inertia of typical 1.4M⊙ neutron stars. In the present work, we study the relative impact of these recent analyses of the 208Pb neutron skin thickness on bulk properties of neutron stars within a Bayesian statistical analysis. Two models for the equation of state prior are employed in order to highlight the role of the highly uncertain high-density equation of state. From our combined Bayesian analysis of nuclear theory, nuclear experiment, and observational constraints on the dense matter equation of state, we find at the 90% credibility level R1.4=12.36−0.73+0.38 km for the radius of a 1.4M⊙ neutron star, R2.0=11.96−0.71+0.94 km for the radius of a 2.0M⊙ neutron star, Λ1.4=440−144+103 for the tidal deformability of a 1.4M⊙ neutron star, and I1.338=1.425−0.146+0.074×1045gcm2 for the moment of inertia of PSR J0737-3039A whose mass is 1.338M⊙.
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- Award ID(s):
- 1652199
- NSF-PAR ID:
- 10465255
- Date Published:
- Journal Name:
- Galaxies
- Volume:
- 10
- Issue:
- 5
- ISSN:
- 2075-4434
- Page Range / eLocation ID:
- 99
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/galaxies10050099
