ABSTRACT
In this work, we delve into the temperature-dependent Equation of State (EoS) of baryonic matter within the framework of the FSU2H* hadronic model, which comprehensively incorporates ...hyperons and is suitable for relativistic simulations of neutron star mergers and supernovae. To assess the impact of the uncertainties in the hyperonic sector on astrophysical observables, we introduce two additional models, namely FSU2H*L (FSU2H*-Lower) and FSU2H*U(FSU2H*-Upper). These models cover the entire spectrum of variability of hyperonic potentials, as derived from experimental data. Our investigations reveal that these uncertainties extend their influence not only to the relative abundances of various particle species but also to the EoS itself and, consequently, have an impact on the global properties of both cold and hot neutron stars. Notably, their effects become more pronounced at large temperatures, owing to the increased presence of hyperons. These findings have direct implications for the outcomes of relativistic simulations of neutron star mergers and supernovae, emphasizing the need of accounting for hyperonic uncertainties to ensure the accuracy and reliability of such simulations in astrophysical contexts.
Cooling of Small and Massive Hyperonic Stars Negreiros, Rodrigo; Tolos, Laura; Centelles, Mario ...
The Astrophysical journal,
08/2018, Letnik:
863, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We perform cooling simulations for isolated neutron stars using recently developed equations of state for their core. The equations of state are obtained from new parametrizations of the FSU2 ...relativistic mean-field functional that reproduce the properties of nuclear matter and finite nuclei, while fulfilling the restrictions on high-density matter deduced from heavy-ion collisions, measurements of massive 2 M neutron stars, and neutron star radii below 13 km. We find that two of the models studied, FSU2R (with nucleons) and in particular FSU2H (with nucleons and hyperons), show very good agreement with cooling observations, even without including extensive nucleon pairing. This suggests that the cooling observations are more compatible with an equation of state that produces a soft nuclear symmetry energy, hence it generates small neutron star radii. However, both models favor large stellar masses, above 1.8 M , to explain the colder isolated neutron stars that have been observed, even if nucleon pairing is present.
The properties of strange pseudoscalar and vectors mesons as well as strange baryon resonances in dense matter are reviewed. Some open questions on the properties of strange hadrons in medium are ...addressed, such as the experimental signatures of inmedium effects coming from the hadronic phase on the final observables in heavy-ion collisions for the experimental conditions at SIS, RHIC and LHC energies.
One of the primary science goals of the next generation of hard x-ray timing instruments is to determine the equation of state of matter at supranuclear densities inside neutron stars by measuring ...the radius of neutron stars with different masses to accuracies of a few percent. Three main techniques can be used to achieve this goal. The first involves waveform modeling. The flux observed from a hotspot on the neutron star surface offset from the rotational pole will be modulated by the star's rotation, and this periodic modulation at the spin frequency is called a pulsation. As the photons propagate through the curved spacetime of the star, information about mass and radius is encoded into the shape of the waveform (pulse profile) via special and general-relativistic effects. Using pulsations from known sources (which have hotspots that develop either during thermonuclear bursts or due to channeled accretion) it is possible to obtain tight constraints on mass and radius. The second technique involves characterizing the spin distribution of accreting neutron stars. A large collecting area enables highly sensitive searches for weak or intermittent pulsations (which yield spin) from the many accreting neutron stars whose spin rates are not yet known. The most rapidly rotating stars provide a clean constraint, since the limiting spin rate where the equatorial surface velocity is comparable to the local orbital velocity, at which mass shedding occurs, is a function of mass and radius. However, the overall spin distribution also provides a guide to the torque mechanisms in operation and the moment of inertia, both of which can depend sensitively on dense matter physics. The third technique is to search for quasiperiodic oscillations in x-ray flux associated with global seismic vibrations of magnetars (the most highly magnetized neutron stars), triggered by magnetic explosions. The vibrational frequencies depend on stellar parameters including the dense matter equation of state, and large-area x-ray timing instruments would provide much improved detection capability. An illustration is given of how these complementary x-ray timing techniques can be used to constrain the dense matter equation of state and the results that might be expected from a 10m super(2) instrument are discussed. Also discussed are how the results from such a facility would compare to other astronomical investigations of neutron star properties.
Proto-neutron stars forming a few seconds after core-collapse supernovae are hot and dense environments where hyperons can be efficiently produced by weak processes. By making use of various ...state-of-the-art supernova simulations combined with the proper extensions of the equations of state including Λ hyperons, we calculate the cooling of the star induced by the emission of dark particles X0 through the decay Λ → nX0. Comparing this novel energy-loss process to the neutrino cooling of SN 1987A allows us to set a stringent upper limit on the branching fraction, BR (Λ → nX0) ≤ 8 × 10−9, that we apply to massless dark photons and axions with flavor-violating couplings to quarks. We find that the new supernova bound can be orders of magnitude stronger than other limits in dark-sector models.
The momentum dependence of the antikaon optical potential in nuclear matter is obtained from a microscopic and self-consistent calculation using the meson-exchange Jülich
KN
interaction. Two ...self-consistent schemes are discussed, which would lead to substantially different predictions for the width of
K
nuclear bound states. The effect of higher partial waves of the
KN
interaction, beyond the
L=0 component, is studied and found to have moderate but nonnegligible effects on the
K
nuclear potential at zero momentum. At momenta as large as 500 MeV
/c, relevant in the analysis of heavy-ion collisions, the higher partial partial waves modify the
K
optical potential by nearly a factor of two.
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