Abstract
There is currently tremendous interest in the role of hyperons and other exotic forms of matter in neutron stars. This is particularly so following the measurement by Demorest et al. of a star with a mass almost 2 solar masses. Given that we know of no physical mechanism to stop the occurrence of hyperons at matter in beta–equilibrium above roughly 3 times nuclear matter density, we discuss the constraints on the possible maximum mass when hyperons are included in the equation of state. The discussion includes a careful assessment of the constraints from low energy nuclear properties as well as the properties of hypernuclei. The model within which these calculations are carried out is the quark-meson coupling (QMC) model, which is derived starting at the quark level.
Highlights
IntroductionThe recent observations of not one but two high mass neutron stars, the millisecond pulsar, PSR J1614-2230 at 1.97 ± 0.04 M [6] and more recently of PSR J0348+0432 at 2.03 ± 0.04 M [5], have imposed the most stringent constraints to date on the equation of state (EoS) of dense matter
The recent observations of not one but two high mass neutron stars, the millisecond pulsar, PSR J1614-2230 at 1.97 ± 0.04 M [6] and more recently of PSR J0348+0432 at 2.03 ± 0.04 M [5], have imposed the most stringent constraints to date on the equation of state (EoS) of dense matter. These observations have spurred re-examinations of exotic forms of matter and, in particular, led to questions of whether or not hyperons can play a significant role in interior of neutron stars, given the anticipated softening of EoS
We find that the stability under variation of the very small number of adjustable parameters is such that if a star were discovered with a mass significantly above 2.1 M, we would need to consider more exotic physics, because it could not be accommodated within the current version of quark-meson coupling (QMC) model
Summary
The recent observations of not one but two high mass neutron stars, the millisecond pulsar, PSR J1614-2230 at 1.97 ± 0.04 M [6] and more recently of PSR J0348+0432 at 2.03 ± 0.04 M [5], have imposed the most stringent constraints to date on the equation of state (EoS) of dense matter. Our discussion includes assessment of low energy nuclear and hypernuclear properties within a relativistic quark level model, the Quark-Meson Coupling (QMC) model This model was used in the earlier work of Stone et al [7], who already predicted the existence of neutron stars containing hyperons with masses as large as 2 M in 2007. We find that the stability under variation of the very small number of adjustable parameters is such that if a star were discovered with a mass significantly above 2.1 M , we would need to consider more exotic physics, because it could not be accommodated within the current version of QMC model
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