arXiv subjects

Andrey Yudin

Publications and source records attributed to Andrey Yudin.

7 recordsLinked to original sources

arXiv2025

Non-conservative Mass Transfer in the Neutron Star Stripping Model

The process of long-term stable mass transfer (or stripping) in a close neutron star binary system is possible at a sufficiently large initial asymmetry of the component masses. At the final stage of the evolution of such systems, the low-mass neutron star fills its Roche lobe, whereupon its mass is gradually transferred to the more massive component. At a certain point, the stability of the mass transfer is lost, causing the minimum-mass neutron star to explode. In the present stripping calculations, the effect of non-conservative mass transfer has been taken into account for the first time, resulting in an increase in the duration of stable mass transfer from a few tenths of a second to a few seconds. This allows the time delay of 1.7 s between the loss of the gravitational-wave signal and the detection of the gamma-ray burst from the multimessenger event GW170817-GRB170817A to be naturally explained. The interaction of the envelope of the exploded minimum-mass neutron star with the matter ejected during non-conservative mass transfer may explain two episodes in the light curve of this gamma-ray burst.

astro-ph.HE↗

arXiv2024

The Influence of a Shock on the Nucleosynthesis Developing during the Explosion of a Low-Mass Neutron Star

The pattern of nucleosynthesis during the explosion of a low-mass neutron star formed in a close binary system in the stripping scenario is considered. In the scenario considered the shock arising during the explosion is shown to strongly heat the expanding neutron star matter. The heavy nuclei produced at the preceding stage of nucleosynthesis are partially destroyed as a result of a sharp increase in the role of photonuclear reactions. It is shown that even short-term heating of the matter by the shock can exert a noticeable influence on the results of the synthesis of elements in the r-process in the inner crust matter, while explosive nucleosynthesis gives rise to new elements in the outer crust matter with mass numbers A from 50 to 130.

astro-ph.HE↗

arXiv2024

Stripping of a neutron star in a close binary system in a pair with a black hole

We consider the final evolutionary stages of a neutron star-black hole pair. According to the current paradigm, such systems eventually coalesce, which in some cases is accompanied by neutron-star tidal disruption. Using analytical methods, we show that the scenario of slow (of the order of several seconds) neutron-star stripping by the black hole is also possible, depending on the system parameters (the initial masses and intrinsic angular momenta of the components, the equation of state for the neutron star). Reaching the lower mass limit (about one tenth of the solar mass), the neutron star explodes to produce a comparatively powerful electromagnetic transient. Our population calculations show that the stripping mechanism is possible in 50-90% of the cases among all coalescing neutron star-black hole pairs, depending on the model assumptions about the evolution of close binary systems (the common-envelope efficiency parameter, the supernova explosion mechanism) and the initial metallicity of the stellar population. Because of the large mass of the ejected material, the kilonova emission in this scenario has good prospects of detection.

astro-ph.HE↗

arXiv2024

Accretion spin-up of the massive component in the neutron star stripping model for short gamma-ray bursts

In this paper, we use analytical methods to study the last stages of the double neutron star (NS) system evolution. Depending on the initial masses of the components, this evolution can occur either in the framework of the merging scenario or in the NS stripping model. The main new ingredient of this work, compared with the previous calculations, is accounting for accretion spin-up of the massive component. This effect leads to a significant decrease in the duration of the stable mass transfer of matter in the stripping mechanism. Within the framework of the Newtonian approximation, we determine the mass boundary between the merging and stripping scenarios. It is shown that this boundary weakly depends on the total mass of the system and the specific form of the NS equation of state and is determined mainly by the initial mass ratio of the components. The stripping scenario is realized at M2/M1<0.8, so it should make a large contribution to the population of close to us gravitational wave events from NS-NS coalescing binaries and accompanying short gamma-ray bursts. Nevertheless, the value obtained requires further clarification, taking into account relativistic effects, possible non-conservative mass transfer, etc.

astro-ph.HE↗

arXiv2023

Dynamics of direct impact accretion in degenerate binary systems

We consider the gas dynamics in an accreting binary system of degenerate stars within the framework of the Newtonian approximation. In such a system, the accretion stream can impact the surface of a white dwarf (WD) or neutron star (NS) as a result of the very compact orbit. This causes a loss of angular momentumfrom the orbit and spin-up of the accretor. We construct approximations for the specific angular momentum of the accreting matter which goes to spin up the accretor and some other parameters of the system. It is shown that the obtained approximation of the specific momentum is qualitatively different from the widely used Keplerian formula. It should affect the boundary between scenarios of immediate tidal disruption and slow mass loss of the donor in WD-WD and NS-NS binaries, as well as the time of stable mass transfer in the stripping scenario.

astro-ph.SR↗

arXiv2018

Asymmetric Nuclear Light Clusters In Supernova Matter

We explore the appearance of light clusters at high densities of collapsing stellar cores. Special attention is paid to the unstable isotope H4, which was not included in previous studies. The importance of light clusters in the calculation of rates for neutrino matter interaction is discussed. The main conclusion is that thermodynamic quantities are only weakly sensitive to the chemical composition. The change in pressure and hence the direct change in collapse dynamics will be minor. But the change in neutrino heating and neutronization processes can be significant.

nucl-th↗

arXiv2016

Hot third family of compact stars and the possibility of core-collapse supernova explosions

A phase transition to quark matter can lead to interesting phenomenological consequences in core-collapse supernovae, e.g., triggering an explosion in spherically symmetric models. However, until now this explosion mechanism was only shown to be working for equations of state that are in contradiction with recent pulsar mass measurements. Here, we identify that this explosion mechanism is related to the existence of a third family of compact stars. For the equations of state investigated, the third family is only pronounced in the hot, early stages of the protocompact star and absent or negligibly small at zero temperature and thus represents a novel kind of third family. This interesting behavior is a result of unusual thermal properties induced by the phase transition, e.g., characterized by a decrease of temperature with increasing density for isentropes, and can be related to a negative slope of the phase transition line in the temperature-pressure phase diagram.

nucl-th↗