arXiv subjects

S. I. Blinnikov

Publications and source records attributed to S. I. Blinnikov.

At least 19 recordsLinked to original sources

arXiv2026

Microlensing by Cluster of Primordial Black Holes

Numerous microlensing survey programs have constrained the possibility of dark matter existing in the form of compact objects within the Galactic halo. These constraints on the dark matter fraction were derived under the assumption of isolated, widely separated objects. This work investigates microlensing by primordial black holes (PBHs) organized into clusters. In this scenario, it is necessary to account for both the influence of neighboring PBHs and the collective gravitational potential of the entire cluster, which significantly complicates the microlensing light curve. Events exhibiting such complex light curves elude detection in observational experiments such as MACHO, EROS, OGLE, POINT-AGAPE, and HSC. It is demonstrated that a significant fraction of PBH dark matter (up to 93\% for the models studied) remains undetected in these observational data. However, for all considered cluster models, a substantial population of PBHs still behaves as isolated lenses. Consequently, the clustering of PBHs does not completely eliminate the microlensing constraints on the PBH contribution to dark matter.

astro-ph.CO↗

arXiv2026

Numerical Study of Polytropes with n=1 and Differential Rotation

The solution space of differentially rotating polytropes with n=1 has been studied numerically. The existence of three different types of configurations: from spheroids to thick tori, hockey puck-like bodies and spheroids surrounded by a torus, separate from or merging with the central body has been proved. It has been shown that the last two types appear only at moderate degrees of rotation differentiality, sigma~2. Rigid-body or weakly differential rotation, as well as strongly differential, have not led to any "exotic" types of configurations. Many calculated configurations have had extremely large values of parameter tau, which has raised the question of their stability with respect to fragmentation.

gr-qc↗

arXiv2024

Opacity of Ejecta in Calculations of Supernova Light Curves

The plasma opacity in stars depends mainly on the local state of matter (the density, temperature, and chemical composition at the point of interest), but in supernova ejecta it also depends on the expansion velocity gradient, because the Doppler effect shifts the spectral lines differently in different ejecta layers. This effect is known in the literature as the expansion opacity. The existing approaches to the inclusion of this effect, in some cases, predict different results in identical conditions. In this paper we compare the approaches of Blinnikov (1996) and Friend and Castor (1983) - Eastman and Pinto (1993) to calculating the opacity in supernova ejecta and give examples of the influence of different approximations on the model light curves of supernovae.

astro-ph.SR↗

arXiv2023

Novel hydrodynamic cumulation mechanism caused by quantum shell effects

The computational and theoretical analysis carried out in this article demonstrates the existence of a nontrivial mechanism for the compression of a submicron-sized gas bubble formed by a gas of classical ions and a gas of degenerate electrons. This mechanism fundamentally differs from conventional compression mechanisms. It is shown that taking into account the quantum effect of a large spatial scale in the distribution of electrons qualitatively changes the character of cumulative processes. Because of a large-scale electric field caused by quantum shell effects, the compression process is characterized by the formation of multiple shock waves. The values of gas temperature and pressure achieved during compression occur higher by two orders of magnitude as compared with the classical adiabatic regime. The analysis is carried out within the framework of the following model: the dynamics of the electron subsystem is described by equations of a quantum electron fluid, while the hydrodynamic approximation is adopted for the ionic subsystem. The large scale effect is taken into account by means of effective external field acting on electrons. The theoretical analysis carried out within this approach clarifies the nature of the cumulative process in the system under consideration; some quantitative characteristics obtained with numerical simulation are presented. The possibility of experimental observation of this cumulative mechanism is analyzed. It is suggested that the manifestation of the effect can be observed during laser compression of a system of submicron targets by measuring the neutron yield.

physics.plasm-ph↗

arXiv2023

Thermal Neutrinos from the Explosion of a Minimum-Mass Neutron Star

We present our calculations of the thermal neutrino radiation that accompanies the explosion of a minimum-mass neutron star. In this case, the neutrino luminosity is lower than the luminosity during a supernova explosion approximately by five orders of magnitude, while the energy carried away by neutrinos is low compared to the explosion energy. We also show that the energy losses through neutrinos do not hinder the envelope heating and the cumulation of the shock during its breakout and the acceleration of the outer part of the envelope to ultrarelativistic speeds.

astro-ph.HE↗

arXiv2022

X-ray signature of antistars in the Galaxy

The existence of macroscopic objects from antimatter (antistars) is envisaged in some models of baryogenesis. Searches for antistars has been usually carried out in gamma-rays through hadronic annihilation of matter. In astrophysically plausible cases of the interaction of neutral atmospheres or winds from antistars with ionized interstellar gas, the hadronic annihilation will be preceded by the formation of excited $p\bar p$ and He$\bar p$ atoms. These atoms rapidly cascade down to low levels prior to annihilation giving rise to a series of narrow lines which can be associated with the hadronic annihilation gamma-ray emission. The most significant are L (3p-2p) 1.73 keV line (yield more than 90\%) from $p\bar p$ atoms, and M (4-3) 4.86 keV (yield $\sim 60\% $) and L (3-2) 11.13 keV (yield about 25\%) lines from $^4$He$\bar p$ atoms. These lines can be probed in dedicated observations by forthcoming sensitive X-ray spectroscopic missions XRISM, \textit{Athena, \textit{Lynx}and in wide-field X-ray surveys like SRG/\textit{eROSITA} all-sky survey.

astro-ph.HE↗

arXiv2021

Parameters of the type-IIP supernova SN 2012aw

We present the results the photometric observations of the Type IIP supernova SN 2012aw obtained for the time interval from 7 till 371 days after the explosion. Using the previously published values of the photospheric velocities we've computed the hydrodynamic model which simultaneously reproduced the photometry observations and velocity measurements. The model was calculated with the multi-energy group radiation hydrodynamics code STELLA. We found the parameters of the pre-supernova: radius $R = 500 R_\odot$, nickel mass $M(^{56}$Ni$)$ $\sim 0.06 M_\odot$, pre-supernova mass $25 M_\odot$, mass of ejected envelope $23.6 M_\odot$, explosion energy $E \sim 2 \times 10^{51}$ erg. The model progenitor mass $M=25 M_\odot$ significantly exceeds the upper limit mass $M=17 M_\odot$, obtained from analysis the pre-SNe observations. This result confirms once more that the 'Red Supergiant Problem' must be resolved by stellar evolution and supernova explosion theories in interaction with observations.

astro-ph.HE↗

arXiv2020

Study of the Dependence of the Plateau Shape for Type II Supernovae on Metallicity

We consider the effect of a change in the rate of flux decline in the U band for type II-P supernovae (SNe IIP) as a function of metallicity $Z$. Based on this effect, we propose a new method to determine the photometric redshift from the SN IIP light curve in the U band. Using the STELLA code, we have constructed model light curves in different bands for different redshifts $z = 0.0, 0.1$, and $0.3$ as the metallicity in the models decreases from $Z \sim 10^{-3}$ to $\sim 10^{-6}$. The flux in the U band is shown to reach a plateau at the lowest metallicities. We consider the influence of other parameters as well: the presupernova mass and the mass of radioactive nickel-56.

astro-ph.HE↗

arXiv2020

Discovery of a hot ultramassive rapidly rotating DBA White Dwarf

We report the discovery of a nearby massive white dwarf with He-H atmosphere. The white dwarf is located at a distance of $74.5\pm0.9$ pc. Its radius, mass, effective temperature, H/He ratio and age are $R=2500\pm100$ km, $M=1.33\pm0.01$ $\rm M_{\odot}$, $T_{\mathrm{eff}}=31200\pm 1200$ K, ${\mathrm{H/He}}\sim0.1$ and $330\pm40$ Myr, respectively. The observed spectrum is redshifted by $V_{\mathrm{r}}=+240\pm15$ km s$^{-1},$ which is mostly attributed to the gravitational redshift. The white dwarf shows a regular stable photometric variability with amplitude $Δg\approx0.06^{\mathrm{m}}$ and period $P=353.456$ s suggesting rapid rotation. This massive, hot and rapidly rotating white dwarf is likely to originate from the merging of close binary white dwarf system that avoided explosion in a thermonuclear type Ia supernova at the Carboniferous Period of the Earth history.

astro-ph.SR↗

arXiv2020

Low-Mass Neutron Stars with Rotation

The properties of low-mass neutron stars with rigid rotation are considered. The possible evolution paths of such stars in a close binary system with mass transfer are calculated. The properties of the gamma-ray burst GRB 170817A interpreted in terms of the stripping model, a natural ingredient of which is the explosion of a low-mass neutron star - a binary component, are briefly discussed.

astro-ph.HE↗

arXiv2019

Analytical Model of Time-Dependent Ionization in the Envelopes of Type II Supernovae at the Photospheric Phase

We investigate a simplified kinetic system of the hydrogen atom (two levels plus continuum) under conditions of a type IIP supernova at the plateau phase that realistically describes the basic properties of the complete system. We have found the Lyapunov function for the reduced system using which we have analytically obtained the ionization freeze-out effect on long time scales. Since the system completely recombines in the equilibrium approximation on long time scales, which does not occur in reality, this result confirms the necessity of allowance for the time-dependent effect in the kinetics during the photospheric phase in a supernova explosion.

astro-ph.SR↗

arXiv2019

Dynamics of supernova bounce in laboratory

We draw attention to recent high explosive (HE) experiments which provide compression of macroscopic amount of matter to high, even record, values of pressure in comparison with other HE experiments. The observed bounce after the compression corresponds to processes in core-collapse supernova explosions after neutrino trapping. Conditions provided in the experiments resemble those in core-collapse supernovae, permitting their use for laboratory astrophysics. A unique feature of the experiments is compression at low entropy. The values of specific entropy are close to those obtained in numerical simulations during the process of collapse in supernova explosions, and much lower than those obtained at laser ignition facilities, another type of high-compression experiment. Both in supernovae and HE experiments the bounce occurs at low entropy, so the HE experiments provide a new platform to realize some supernova collapse effects in laboratory, especially to study hydrodynamics of collapsing flows and the bounce. Due to the good resolution of diagnostics in the compression of macroscopic amounts of material with essential effects of nonideal plasma in EOS, and observed development of 3D instabilities, these experiments may serve as a useful benchmark for astrophysical hydrodynamic codes.

physics.plasm-ph↗

arXiv2018

Exploding neutron stars in close binaries

The discovery of GW signal from merging neutron stars by LIGO on 17th August 2017 was followed by a short GRB170817A discovered by FERMI and INTEGRAL 1.7 seconds after the loss of the GW signal when it just reached its maximum. Here we present a reproduction of the first paper (published by us in 1984) predicting a short GRB after GW signal of merging neutron stars. Our paper followed the scenario by Clark and Eardley (1977) who predicted a catastrophic disruption of a neutron star in a binary 1.7 seconds after the peak of GW signal. Our next paper in 1990 predicted all the main properties of the short GRB with quite a reasonable accuracy. Typos in English translation are corrected and a few comments are added in the current publication as numbered footnotes (the only footnote from the original paper is marked by an asterisk).

astro-ph.HE↗

arXiv2018

Quantum shell effects in compressed mesoscopic system

The article demonstrates the nontrivial manifestation of quantum shell effects in a compressed mesoscopic system. It is shown that there are two spatial scales in the distribution of degenerate electrons in a spherical well. The first scale is the Fermi length $\sim h/p_{\rm F}$. By quantum shell effect, the authors mean the existence of the new spatial scale, which is order of the system size and much larger than the first scale. The theoretical analysis for the large amount of free electrons ($N \lesssim 10^9$) in an infinite spherical well demonstrates what causes the appearance of the spatial nonuniformity and gives analytical expression for the electron distribution function. These results are confirmed by a numerical summation of exact solutions for the electron wave functions in an infinite potential well. It is shown that an analogous effect for the spatial distribution of electrons exists in a compressed hydrogen gas bubble of submicron size ($<0.1 μm$). The numerical simulation of the electron distribution was carried out by the DFT (Density Functional Theory) method. The consequence of this effect is the nontrivial dynamics of the compressible cold gas bubble. This system can be realized in the thermonuclear experiments. The limiting factors of the analyzed effect are considered: symmetry of system, electron temperature, and curvature of system boundary.

physics.plasm-ph↗

arXiv2018

Distance Estimate of Tycho's SNR

We present an approach to finding distances to young supernova remnants. Our method is based on hydrodynamical simulations of Tycho's SNR using the SUPREMNA code. For the explosion models, we use the classical W7 deflagration model and the delayed detonation model that was previously shown to provide good fits to the X-ray emission of Tycho's SNR. Combining our hydrodynamical simulations with the Chandra high-resolution images of the remnant obtained in 2015, we derive a distance estimate to Tycho's SNR of $2.8\pm 0.4$ kpc.

astro-ph.HE↗

arXiv2017

A young contracting white dwarf in the peculiar binary HD 49798/RX J0648.0--4418?

HD 49798/RX J0648.0--4418 is a peculiar X-ray binary with a hot subdwarf (sdO) mass donor. The nature of the accreting compact object is not known, but its spin period $P=13.2$~s and $\dot P =-2.15 \times 10^{-15}$s~s$^{-1}$, prove that it can be only either a white dwarf or a neutron star. The spin-up has been very stable for more than 20 years. We demonstrate that the continuous stable spin-up of the compact companion of HD 49798 can be best explained by contraction of a young white dwarf with an age $\sim 2$~Myrs. This allows us to interpret all the basic parameters of the system in the framework of an accreting white dwarf. We present examples of binary evolution which result in such systems. If correct, this is the first direct evidence for a white dwarf contraction on early evolutionary stages.

astro-ph.HE↗

arXiv2017

Time-Dependent Ionization in theEnvelopes of Type II Supernovae at the Photospheric Phase

The importance of allowance for the time-dependent effect in the kinetics at the photospheric phase during a supernova explosion has been confirmed by several independent research groups. The time-dependent effect provides a higher degree of hydrogen ionization in comparison with the steady-state solutions and strengthens the H$α$ line in the resulting simulated spectrum, with the intensity of the effect increasing with time. However, some researchers argue that the time-dependent ionization effect is unimportant. Its allowance leads to an insignificant strengthening of H$α$ in their modeling only in the first days after explosion. We have demonstrated the importance of the time-dependent effect with the models of SN 1999em as an example using the new original LEVELS software package. The role of a number of factors that can weaken the time-dependent effect has been checked. We have confirmed that the intensity of the effect is affected by the abundance of metal admixtures in the envelope, while the addition of extra levels to themodel hydrogen atom weakens the time-dependent effect to a lesser degree and never removes it completely.

astro-ph.SR↗

arXiv2016

Multicolour modelling of SN 2013dx associated with GRB 130702A

We present optical observations of SN 2013dx, related to the Fermi burst GRB 130702A occurred at a redshift z = 0.145. It is the second-best sampled GRB-SN after SN~1998bw: the observational light curves contain more than 280 data points in uBgrRiz filters until 88 day after the burst, and the data were collected from our observational collaboration (Maidanak Observatory, Abastumani Observatory, Crimean Astrophysical Observatory, Mondy Observatory, National Observatory of Turkey, Observatorio del Roque de los Muchachos) and from the literature. We model numerically the multicolour light curves using the one-dimensional radiation hydrodynamical code STELLA, previously widely implemented for the modelling of typical non-GRB SNe. The best-fitted model has the following parameters: pre-supernova star mass M = 25 M_Sun, mass of a compact remnant M_CR = 6 M_Sun, total energy of the outburst E_oburst = 3.5 x 10^(52) erg, pre-supernova star radius R = 100 R_Sun, M_56Ni = 0.2 M_Sun which is totally mixed through the ejecta; M_O = 16.6 M_Sun, M_Si = 1.2 M_Sun, and M_Fe = 1.2 M_Sun, and the radiative efficiency of the SN is 0.1 per cent.

astro-ph.HE↗