arXiv subjects

Sebastian Kubis

Publications and source records attributed to Sebastian Kubis.

15 recordsLinked to original sources

arXiv2025

Examining the possibility of a thick crust in the compact stellar object HESS J1731-347

A relativistic mean-field model with a crossing term of isovector-scalar and isoscalar mesons, the Cracow crossing terms (CCT) model, has previously been shown to be capable of explaining the light and compact object HESS J1731-347 [11]. Here, the model is supplemented with a correct treatment of the phase transition. Applying the thermodynamically consistent Gibbs conditions shows that a mixed-phase system occurs in the core of the neutron star over a wide range of densities, extending up to the neutron star crust, leading to an intriguing stellar structure with a thick and massive crust.

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arXiv2023

Relativistic mean field model for ultra-compact low mass neutron star of HESS J1731-347

The recent observation of the object HESS J1731-347 suggests the existence of a very light and very compact neutron star being a challenge for commonly used equation of state for dense matter. In this work we present a relativistic mean field model enriched with meson crossing terms among isovector and isoscalar mesons. Such interactions particularly dominate the behavior of the symmetry energy and accounts for small size of compact star radius. The proposed model fulfill the recent constraints concerning the symmetry energy slope and state-of-the-art compact stars constraints derived from the NICER measurements of PSR J0030+0451 and PSR J0740+6620 pulsars as well as from the GW170817 event and its associated electromagnetic counterparts AT2017gfo/GRB170817A.

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arXiv2021

The role of the electric Bond number in the stability of pasta phases

The stability of pasta phases in cylindrical and spherical Wigner-Seitz (W-S) cells is examined. The electric Bond number is introduced as the ratio of electric and surface energies. In the case of a charged rod in vacuum, other kinds of instabilities appear in addition to the well known Plateau- Rayleigh mode. For the case of a rod confined in a W-S cell the variety of unstable modes is reduced. It comes from the virial theorem, which bounds the value of the Bond number from above and reduces the role played by electric forces. A similar analysis is done for the spherical W-S cell, where it appears that the inclusion of the virial theorem stabilizes all of the modes.

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arXiv2020

Multilayer neutron stars with scalar mesons crossing term

It is shown that recently proposed RMF model with $\sigma$ and $\delta$ meson interaction agrees with the observational data and presents an interesting structure with phase transition in the outer part of neutron star core.

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arXiv2020

Oscillating Strange Quark Matter Objects Excited in Stellar Systems

It is shown that strange quark matter (SQM) objects, stars, and planets, can very efficiently convert the mechanical energy into hadronic energy when they oscillate. This is because the mass density at the edge of SQM objects, $\rho_0{=}4.7{\times}10^{14}\frac{\mathrm{g}}{\mathrm{cm}^3}$, is the critical density below which SQM is unstable with respect to decay into photons, hadrons, and leptons. We consider here radial oscillations of SQM objects that could be induced in stellar or planetary systems where tidal interactions are ubiquitous. Oscillations of $0.1\%$ radius amplitude already result in $1\,$keV per unit baryon number excitation near the surface of SQM stars. The excitation energy is converted into electromagnetic energy in a short time of 1 ms, during a few oscillations. Higher amplitude oscillations result in faster energy release that could lead to fragmentation or dissolution of SQM stars. This would have significant consequences for hypothetical SQM star binaries and planetary systems of SQM planets with regard to gravitational wave emission.

astro-ph.HE↗

arXiv2018

Influence of the interactions of scalar mesons on the behavior of the symmetry energy

Symmetry energy behavior of scalar mesons interactions is analyzed within the framework of the standard relativistic mean field model. Whereas the presence of the $\delta$ meson itself makes the symmetry energy stiffer, the crossing term $\delta\textrm{-}\sigma$ allows its slope to decrease to the suggested experimental value. Moreover, such controlling of the symmetry energy does not significantly affect the stiffness of the equation of state and acceptable neutron star masses result. Interestingly, for the most plausible value of the symmetry energy slope, the phase transition occurs in the neutron star core.

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arXiv2017

Topological analysis of nuclear pasta phases

In this paper the analysis of the result of numerical simulations of pasta phases using algebraic topology methods is presented. These considerations suggest that some phases can be further split into (sub)phases and therefore should be more refined in numerical simulations. The results presented in the paper can also be used to relate the Euler characteristic from numerical simulations to the geometry of the phases. The Betti numbers are used as they provide finer characterization of the phases. It is also shown that different boundary conditions give different outcomes.

astro-ph.HE↗

arXiv2017

Shape stability of pasta phases: Lasagna case

The stability of periodically placed slabs occurring in neutron stars (lasagna phase) is examined by exact geometrical methods for the first time. It appears that the slabs are stable against any shape perturbation modes for the whole range of volume fraction occupied by the slab. The calculations are done in the framework of the liquid drop model and obtained results are universal - they do not depend on model parameters like surface tension or charge density. The results shows that the transition to other pasta shapes requires crossing the finite energy barrier

astro-ph.HE↗

arXiv2015

Exact solution of equations for proton localization in neutron star matter

The rigorous treatment of proton localization phenomenon in asymmetric nuclear matter is presented. The solution of proton wave function and neutron background distribution is found by the use of the extended Thomas-Fermi approach. The minimum of energy is obtained in the Wigner- Seitz approximation of spherically symmetric cell. The analysis of three different nuclear models suggests that the proton localization is likely to take place in the interior of neutron star.

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arXiv2012

Symmetry energy effects in the neutron star properties

The functional form of the nuclear symmetry energy has only been determined in a very narrow range of densities. Uncertainties concern both the low as well as the high density behaviour of this function. In this work different shapes of the symmetry energy, consistent with the experimental data, were introduced and their consequences for the crustal properties of neutron stars are presented. The resulting models are in agreement with astrophysical observations.

astro-ph.SR↗

arXiv2012

Systematic analysis of symmetry energy effects in the neutron star crust properties

The functional form of the nuclear symmetry energy in the whole range of densities relevant for the neutron stars is still unknown. Discrepancies concern both the low as well as the high density behaviour of this function. By use of Bezier curves three different families of the symmetry energy shapes, relevant for different density range were introduced. Their consequences for the crustal properties of neutron stars are presented.

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arXiv2010

SQM stars around pulsar PSR B1257+12

Following Wolszczan's landmark discovery of planets in orbit around pulsar PSR B1257+12 in 1991, over 300 planets in more than 200 planetary systems have been found. Therefore, the meaning of Wolszczan's discovery cannot be overestimated. In this paper we aim to convince the reader that the objects accompanying pulsar PSR B1257+12 are more exotic than thought so far. They might not be ordinary planets but dwarf strange quark stars, whereas the pulsar might be a quark star with standard mass, not a neutron star. If this was the case, it would indicate that strange quark matter is the ground state of matter.

astro-ph.EP↗

arXiv2006

The nuclear symmetry energy and stability of matter in neutron star

It is shown that behavior of the nuclear symmetry energy is the key quantity in the stability consideration in neutron star matter. The symmetry energy controls the position of crust-core transition and also may lead to new effects in the inner core of neutron star.

astro-ph↗

arXiv2005

Neutrino emissivity under neutral kaon condensation

Neutrino emissivity from neutron star matter with neutral kaon condensate is considered. It is shown that a new cooling channel is opened, and what is more, all previously known channels acquire the greater emissivity reaching the level of the direct URCA cycle in normal matter.

astro-ph↗

arXiv2004

The diffusive instability of kaon condensate in neutron star matter

The beta equilibrated dense matter with kaon condensate is analyzed with respect to extended stability conditions including charge fluctuations. This kind of the diffusive instability, appeared to be common property in the kaon condensation case. Results for three different nuclear models are presented.

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