A Bayesian analysis of the properties of hybrid stars with the NJL model. (arXiv:2112.09595v2 [astro-ph.HE] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Pfaff_A/0/1/0/all/0/1">Antoine Pfaff</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hansen_H/0/1/0/all/0/1">Hubert Hansen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gulminelli_F/0/1/0/all/0/1">Francesca Gulminelli</a>
We implement a Bayesian analysis of the properties of non-rotating hybrid
stars at equilibrium with quark matter cores, as described by the SU(3)
Nambu–Jona-Lasinio (NJL) model. The hadronic phase is described by a unified
metamodeling approach, with a prior parameter space covering the present
uncertainties on nuclear matter properties with nucleonic degrees of freedom.
The parameter space of the NJL model includes vector-isoscalar and
vector-isovector couplings and, additionally, an effective bag constant for the
quark pressure is introduced as a free parameter. The phase transition is
assumed to be first order with charge neutral phases, following the Maxwell
construction. Our Bayesian framework includes filters on the experimental and
theoretical low-density nuclear physics knowledge (atomic masses, ab initio
calculations of the EoS) and high density constraints from astrophysical
observations (maximum mass of J0348+0432, binary tidal deformability of the
GW170817 event). We find that microscopic vector interactions play an important
role in quark matter in order to stiffen the equation of state sufficiently to
reach high star masses, in agreement with previous studies. Even within a very
large prior for both the hadronic phase and the quark phase and the important
freedom brought by the effective bag constant, our posterior quark cores tend
to be relatively small and only appear in very heavy stars ($Mgtrsim 2
M_odot$). Coincidentally, the inclusion of the nucleon-quark transition
(deconfinement transition) only weakly affects the radii of compact stars,
foreshadowing a very low observability of a possible phase transition using
x-ray radii measurements.
We implement a Bayesian analysis of the properties of non-rotating hybrid
stars at equilibrium with quark matter cores, as described by the SU(3)
Nambu–Jona-Lasinio (NJL) model. The hadronic phase is described by a unified
metamodeling approach, with a prior parameter space covering the present
uncertainties on nuclear matter properties with nucleonic degrees of freedom.
The parameter space of the NJL model includes vector-isoscalar and
vector-isovector couplings and, additionally, an effective bag constant for the
quark pressure is introduced as a free parameter. The phase transition is
assumed to be first order with charge neutral phases, following the Maxwell
construction. Our Bayesian framework includes filters on the experimental and
theoretical low-density nuclear physics knowledge (atomic masses, ab initio
calculations of the EoS) and high density constraints from astrophysical
observations (maximum mass of J0348+0432, binary tidal deformability of the
GW170817 event). We find that microscopic vector interactions play an important
role in quark matter in order to stiffen the equation of state sufficiently to
reach high star masses, in agreement with previous studies. Even within a very
large prior for both the hadronic phase and the quark phase and the important
freedom brought by the effective bag constant, our posterior quark cores tend
to be relatively small and only appear in very heavy stars ($Mgtrsim 2
M_odot$). Coincidentally, the inclusion of the nucleon-quark transition
(deconfinement transition) only weakly affects the radii of compact stars,
foreshadowing a very low observability of a possible phase transition using
x-ray radii measurements.
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