2015A&A...576A..68F


C.D.S. - SIMBAD4 rel 1.7 - 2019.10.23CEST01:03:26

2015A&A...576A..68F - Astronomy and Astrophysics, volume 576A, 68-68 (2015/4-1)

Neutron stars with hyperon cores: stellar radii and equation of state near nuclear density.

FORTIN M., ZDUNIK J.L., HAENSEL P. and BEJGER M.

Abstract (from CDS):

The existence of 2M pulsars puts very strong constraints on the equation of state (EOS) of neutron stars (NSs) with hyperon cores, which can be satisfied only by special models of hadronic matter. The radius-mass relation for these models is sufficiently specific that it could be subjected to an observational test with future X-ray observatories. We want to study the impact of the presence of hyperon cores on the radius-mass relation for NS. We aim to find out how, and for which particular stellar mass range, a specific relation R(M), where M is the gravitational mass, and R is the circumferential radius, is associated with the presence of a hyperon core. We consider a set of 14 theoretical EOS of dense matter, based on the relativistic mean-field approximation, allowing for the presence of hyperons in NSs. We also discuss a recent EOS based on non-relativistic G-matrix theory yielding NSs with hyperonic cores and M>2M. We seek correlations between R(M) and the stiffness of the EOS below the hyperon threshold needed to pass the 2M test. For NS masses 1.0<M/M<1.6, we get R>13km, because of a very stiff pre-hyperon segment of the EOS. At nuclear density (n0=0.16fm–3), the pressure is significantly higher than a robust upper bound obtained recently using chiral effective field theory. If massive NSs do have a sizable hyperon core, then according to current models the radii for M=1.0-1.6M are necessarily >13km. If, on the contrary, a NS with a radius R(obs)<12km is observed in this mass domain, then sizable hyperon cores in NSs, as we model them now, are ruled out. Future X-ray missions with <5% precision for a simultaneous M and R measurement will have the potential to solve the problem with observations of NSs. Irrespective of this observational test, present EOS allowing for hyperons that fulfill condition Mmax>2M yield a pressure at nuclear density that is too high relative to up-to-date microscopic calculations of this quantity.

Abstract Copyright:

Journal keyword(s): dense matter - equation of state - stars: neutron

Simbad objects: 15

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Number of rows : 15

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 NGC 104 GlC 00 24 05.359 -72 04 53.20   5.78 4.09     ~ 3463 0
2 PSR J0348+0432 Psr 03 48 43.6365407296 +04 32 11.460202882           ~ 121 1
3 PSR J0437-47 Psr 04 37 15.7976203608 -47 15 08.536908257           DC 720 0
4 NGC 5139 GlC 13 26 47.28 -47 28 46.1   6.12 5.33     ~ 2910 0
5 V* QX Nor LXB 16 12 43.0 -52 25 23           ~ 805 1
6 PSR J1614-2230 Psr 16 14 36.5070 -22 30 31.207           ~ 250 1
7 M 13 GlC 16 41 41.634 +36 27 40.75     5.8     ~ 1969 0
8 NGC 6304 GlC 17 14 32.25 -29 27 43.3   10.33 9.03     ~ 280 0
9 KS 1731-260 LXB 17 34 13.46 -26 05 18.6       22.8 20.9 ~ 387 0
10 NGC 6397 GlC 17 40 42.09 -53 40 27.6   7.39 5.17     ~ 1751 1
11 NAME TER 5 X-1 LXB 17 48 05.196 -24 46 47.40           ~ 183 1
12 [PLV2002] CX1 LXB 17 48 52.163 -20 21 32.40           ~ 153 1
13 X Sgr X-4 LXB 18 23 40.57 -30 21 40.6   19.06 18.81     ~ 886 1
14 M 28 GlC 18 24 32.89 -24 52 11.4           ~ 637 0
15 M 30 GlC 21 40 22.12 -23 10 47.5     7.10     ~ 882 0

    Equat.    Gal    SGal    Ecl

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2019.10.23-01:03:26

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