arXiv subjects

A. D. Kaminker

Publications and source records attributed to A. D. Kaminker.

At least 19 recordsLinked to original sources

arXiv2026

Vacuum polarization and cyclotron resonance effects on radiative transfer and plasma deceleration in subcritical X-ray pulsars

We investigate the spectrum and polarization of radiation emerging from a subcritical X-ray pulsar using self-consistent radiation-hydrodynamic simulations of an accretion channel in a strong magnetic field. The polarized radiative transfer in the channel above the hot spot is simulated for the two normal modes, taking into account resonant Compton scattering in a strongly magnetized plasma and the effects of vacuum polarization. We show that the deceleration of the accreting matter in the subcritical regime is mainly governed by resonant scattering. Our simulations provide the velocity profiles of the plasma flow and demonstrate that vacuum polarization dominates over plasma birefringence, enhancing both the cyclotron spectral feature and the radiative deceleration of the plasma. We also find that the energy of the cyclotron feature increases with accretion luminosity, indicating a positive correlation consistent with previous observational results and theoretical interpretation.

astro-ph.HE↗

arXiv2026

Beaming of polarized radiation in subcritical X-ray pulsars

Radiation of X-ray pulsars is powered by accretion on the neutron star surface from a binary companion under the influence of a strong magnetic field. We study beaming of this radiation in the case of subcritical X-ray pulsars, where it is formed in the accretion channel close to the neutron star surface. We solve equations of the hydrodynamics and radiative transfer of two coupled polarization modes in the accretion channel numerically, taking into account resonant Compton scattering and vacuum polarization. The beaming patterns are obtained for different accretion rates, photon energies and polarizations, and for different models of the neutron star surface radiation. The calculated beaming patterns are converted into light curves for both the intensity and polarization, taking into account the effects of General Relativity. These beaming patterns and light curves are found to be strongly affected by the resonant Compton scattering for photon energies comparable with the electron cyclotron energy. In particular, the angular redistribution of radiation near the cyclotron resonance may reduce the light-curve modulation amplitude, which is consistent with observational indications of a suppressed pulsed fraction at these energies.

astro-ph.HE↗

arXiv2023

Neutrino emission of neutron-star superbursts

Superbursts of neutron stars are rare but powerful events explained by the explosive burning of carbon in the deep layers of the outer envelope of the star. In this paper we perform a simulation of superbursts and propose a simple method for describing the neutrino stage of their cooling, as well as a method for describing the evolution of the burst energy on a scale of several months. We note a universal relation for the temperature distribution in the burnt layer at its neutrino cooling stage, as well as the unification of bolometric light curves and neutrino heat loss rates for deep and powerful bursts. We point out the possibility of long-term retention of the burst energy in the star's envelope. The results can be useful for interpretation of superburst observations.

astro-ph.HE↗

arXiv2023

Hydrodynamical simulation of the structure of the X-ray pulsar accretion channel: accounting for resonant scattering

A self-consistent radiation-hydrodynamics model of an accretion channel of subcritical X-ray pulsars is constructed. The influence of the presence of resonance in the scattering cross-section on the accretion process and radiation transfer is taken into account. It is shown that the efficiency of plasma deceleration by radiation depends on the magnitude of the magnetic field $B$. For $B=1.7\times 10^{12}$ G, the spectra and the degree of linear polarization of the radiation of the accretion channel are constructed. In the obtained spectra, the shape of the cyclotron line depends on the direction of the outgoing radiation. The calculated linear polarization degree of the outgoing radiation is $30 -40\%$ near the cyclotron resonance, whereas it can be small ($\lesssim 5 - 10\%$) at energies significantly lower than the resonant one.

astro-ph.HE↗

arXiv2023

Nearly Forgotten Cosmological Concept of E. B. Gliner

E. B. Gliner started his scientific career in 1963 at the age of 40. In 1965, when the existence of the cosmological constant $λ$ seemed unnecessary to most cosmologists, he renewed interest in the problem by emphasizing a material interpretation of de Sitter space (i.e., the space curved in the presence of $λ$). According to that interpretation, the curvature is produced by a cosmological vacuum (now identified as dark energy of the universe). In 1970, Gliner proposed a description of exponential expansion (or contraction) of the universe at the early (or late) evolution stage dominated by cosmological vacuum. In 1975, Gliner (with I.G. Dyminikova) suggested a model of the early universe free of Big Bang singularity, and developed a scenario of nonsingular Friedmann cosmology. Many of these findings were used in the modern inflation scenarios of the universe, first proposed by A.A. Starobinsky (1979) and A. Guth (1981) and greatly multiplied later. However, these inflation scenarios differ from the scenario of Gliner and Dymnikova, and Gliner's contribution to cosmology is nearly forgotten. The history and the essence of this contribution are outlined, as well the difference from the inflation theories.

physics.hist-ph↗

arXiv2020

Model of heat diffusion in the outer crust of bursting neutron stars

We study heat diffusion after an energy release in a deep spherical layer of the outer neutron star crust (10^7 < ρ< 4 x 10^{11} g/cm^3). We demonstrate that this layer possesses specific heat-accumulating properties, absorbing heat and directing it mostly inside the star. It can absorb up to about 10^{43}-10^{44} erg due to its high heat capacity, until its temperature exceeds T ~ 3 x 10^9 K and triggers a rapid neutrino cooling. A warm layer with T ~ 10^8 - 3 x 10^9 K can serve as a good heat reservoir, which is thermally decoupled from the inner crust and the stellar core for a few months. We present a toy model to explore the heat diffusion within the heat-accumulating layer, and we test this model using numerical simulations. We formulate some generic features of the heat propagation which can be useful, for instance, for the interpretation of superbursts in accreting neutron stars. We present a self-similar analysis of late afterglow after such superbursts, which can be helpful to estimate properties of bursting stars.

astro-ph.HE↗

arXiv2018

Afterburst thermal relaxation in neutron star crusts

We study thermal relaxation in a neutron star after internal heating events (outbursts) in the crust. We consider thin and thick spherically symmetric heaters, superfluid and non-superfluid crusts, stars with open and forbidden direct Urca processes in their cores. In particular, we analyze long-term thermal relaxation after deep crustal heating produced by nuclear transformations in fully or partly accreted crusts of transiently accreting neutron stars. This long-term relaxation has a typical relaxation time and an overall finite duration time for the crust to thermally equilibrate with the core. Neutron superfluidity in the inner crust greatly affects the relaxation if the heater is located in the inner crust. It shortens and unifies the time of emergence of thermal wave from the heater to the surface. This is important for the interpretation of observed outbursts of magnetars and transiently accreting neutron stars in quasi-persistent low-mass X-ray binaries.

astro-ph.HE↗

arXiv2016

Theory of neutrino emission from nucleon-hyperon matter in neutron stars: Angular integrals

Investigations of thermal evolution of neutron stars with hyperon cores require neutrino emissivities for many neutrino reactions involving strongly degenerate particles (nucleons, hyperons, electrons, muons). We calculate the angular integrals $I_n$ (over orientations of momenta of $n$ degenerate particles) for major neutrino reactions with $n$ =3, 4, 5 at all possible combinations of particle Fermi momenta. The integrals $I_n$ are necessary ingredients for constructing a uniform database of neutrino emissivities in dense nucleon-hyperon matter. The results can also be used in many problems of physical kinetics of strongly degenerate systems.

astro-ph.HE↗

arXiv2015

Analyzing Neutron Star in HESS J1731-347 from Thermal Emission and Cooling Theory

The central compact object in the supernova remnant HESS J1731-347 appears to be the hottest observed isolated cooling neutron star. The cooling theory of neutron stars enables one to explain observations of this star by assuming the presence of strong proton superfluidity in the stellar core and the existence of the surface heat blanketing envelope which almost fully consists of carbon. The cooling model of this star is elaborated to take proper account of the neutrino emission due to neutron-neutron collisions which is not suppressed by proton superfluidity. Using the results of spectral fits of observed thermal spectra for the distance of 3.2 kpc and the cooling theory for the neutron star of age 27 kyr, new constraints on the stellar mass and radius are obtained which are more stringent than those derived from the spectral fits alone.

astro-ph.SR↗

arXiv2015

Central compact objects in Kes 79 and RCW 103 as "hidden" magnetars with crustal activity

We propose that observations of "hidden" magnetars in central compact objects can be used to probe crustal activity of neutron stars with large internal magnetic fields. Estimates based on calculations by Perna \& Pons (2011), Pons \& Rea (2012) and Kaminker et al. (2014) suggest that central compact objects, which are proposed to be "hidden" magnetars, must demonstrate flux variations on the time scale of months-years. However, the most prominent candidate for the "hidden" magnetars --- CXO J1852.6+0040 in Kes 79, -- shows constant (within error bars) flux. This can be interpreted by lower variable crustal activity than in typical magnetars. Alternatively, CXO J1852.6+0040 can be in a high state of variable activity during the whole period of observations. Then we consider the source 1E161348-5055 in RCW103 as another candidate. Employing a simple 2D-modeling we argue that properties of the source can be explained by the crustal activity of the magnetar type. Thus, this object may be supplemented for the three known candidates for the "hidden" magnetars among central compact objects discussed in literature.

astro-ph.HE↗

arXiv2014

Neutrino-pair bremsstrahlung in a neutron star crust

Based on the formalism by Kaminker et al. (Astron. Astrophys. 343 (1999) 1009) we derive an analytic approximation for neutrino-pair bremsstrahlung emissivity due to scattering of electrons by atomic nuclei in the neutron star crust of any realistic composition. The emissivity is expressed through generalized Coulomb logarithm which we fit by introducing an effective potential of electron-nucleus scattering. In addition, we study the conditions at which the neutrino bremsstrahlung in the crust is affected by strong magnetic fields. The results can be applied for modelling of many phenomena in neutron stars, such as thermal relaxation in young isolated neutron stars and in accreting neutron stars with overheated crust in soft X-ray transients.

astro-ph.SR↗

arXiv2014

Thermal emission of neutron stars with internal heaters

Using 1D and 2D cooling codes we study thermal emission from neutron stars with steady state internal heaters of various intensities and geometries (blobs or spherical layers) located at different depths in the crust. The generated heat tends to propagate radially, from the heater down to the stellar core and up to the surface; it is also emitted by neutrinos. In local regions near the heater the results are well described with the 1D code. The heater's region projects onto the stellar surface forming a hot spot. There are two heat propagation regimes. In the first, conduction outflow regime (realized at heat rates $H_0 \lesssim 10^{20}$ erg cm$^{-3}$ s$^{-1}$ or temperatures $T_\mathrm{h} \lesssim 10^9$ K in the heater) the thermal surface emission of the star depends on the heater's power and neutrino emission in the stellar core. In the second, neutrino outflow regime ($H_0 \gtrsim 10^{20}$ erg cm$^{-3}$ s$^{-1}$ or $T_\mathrm{h} \gtrsim 10^9$ K) the surface thermal emission becomes independent of heater's power and the physics of the core. The largest (a few per cent) fraction of heat power is carried to the surface if the heater is in the outer crust and the heat regime is intermediate. The results can be used for modeling young cooling neutron stars (prior to the end of internal thermal relaxation), neutron stars in X-ray transients, magnetars and high-$B$ pulsars, as well as merging neutron stars.

astro-ph.HE↗

arXiv2014

Quasi-periodical components in the radial distributions of cosmologically remote objects

A statistical analysis of radial (line-of-sight) 1D-distributions of brightest cluster galaxies (BCGs) within the redshift interval $0.044 \leq z \leq 0.78$ and Mg II absorption-line systems ($0.37 \leq z \leq 2.28$) is carried out. Power spectra and two-point radial correlation functions are calculated. It is found that both radial distributions of spectroscopic redshifts of 52,683 BCGs and 32,840 Mg II absorption systems incorporate similar quasi-periodical components relatively to the comoving distance. Significance of the components exceeds $4σ$-level and admits an increase ($\geq 5σ$) for some broad subsamples. For the ΛCDM cosmological model the periodicities correspond to spatial comoving scales ($98 \pm 3$) and ($101 \pm 2$)h$^{-1}$ Mpc, respectively. These quasi-periods turn out to be close to the characteristic scale ($101 \pm 6$)h$^{-1}$Mpc of the quasi-periodical component obtained earlier for the radial distribution of luminous red galaxies (LRGs). On the other hand, the scales are close to the spatial scale corresponding to the baryon acoustic oscillations (BAOs) revealed by many authors at the last decade. Fourier transform phases obtained for the BCGs and LRGs are found to be close, while the phases calculated for the Mg II absorption systems and LRGs are opposite. Discussions of the results in a context of the BAO and large-scale structure characteristic scales are outlined.

astro-ph.CO↗

arXiv2010

Large-scale periodicity in the distribution of QSO absorption-line systems

The spatial-temporal distribution of absorption-line systems (ALSs) observed in QSO spectra within the cosmological redshift interval z = 0.0--4.3 is investigated on the base of our updated catalog of absorption systems. We consider so called metallic systems including basically lines of heavy elements. The sample of the data displays regular variations (with amplitudes ~ 15 -- 20%) in the z-distribution of ALSs as well as in the eta-distribution, where eta is a dimensionless line-of-sight comoving distance, relatively to smoother dependences. The eta-distribution reveals the periodicity with period Delta eta = 0.036 +/- 0.002, which corresponds to a spatial characteristic scale (108 +/- 6) h(-1) Mpc or (alternatively) a temporal interval (350 +/- 20) h(-1) Myr for the LambdaCDM cosmological model. We discuss a possibility of a spatial interpretation of the results treating the pattern obtained as a trace of an order imprinted on the galaxy clustering in the early Universe.

astro-ph.CO↗

arXiv2009

Heating and cooling of magnetars with accreted envelopes

We study the thermal structure and evolution of magnetars as cooling neutron stars with a phenomenological heat source in an internal layer. We focus on the effect of magnetized (B > 10^{14} G) non-accreted and accreted outermost envelopes composed of different elements, from iron to hydrogen or helium. We discuss a combined effect of thermal conduction and neutrino emission in the outer neutron star crust and calculate the cooling of magnetars with a dipole magnetic field for various locations of the heat layer, heat rates and magnetic field strengths. Combined effects of strong magnetic fields and light-element composition simplify the interpretation of magnetars in our model: these effects allow one to interpret observations assuming less extreme (therefore, more realistic) heating. Massive magnetars, with fast neutrino cooling in their cores, can have higher thermal surface luminosity.

astro-ph.SR↗

arXiv2007

Theory of cooling neutron stars versus observations

We review current state of neutron star cooling theory and discuss the prospects to constrain the equation of state, neutrino emission and superfluid properties of neutron star cores by comparing the cooling theory with observations of thermal radiation from isolated neutron stars.

astro-ph↗

arXiv2007

The redshift distribution of absorption-line systems in QSO spectra

A statistical analysis of the space-time distribution of absorption-line systems (ALSs) observed in QSO spectra within the cosmological redshift interval $z$=0.0--3.7 is carried out on the base of our catalog of absorption systems (Ryabinkov et al. 2003). We confirm our previous conclusion that the $z$-distribution of absorbing matter contains non-uniform component displaying a pattern of statistically significant alternating maxima (peaks) and minima (dips). Using the wavelet transformation we determine the positions of the maxima and minima and estimate their statistical significance. The positions of the maxima and minima of the $z$-distributions obtained for different celestial hemispheres turn out to be weakly sensitive to orientations of the hemispheres. The data reveal a regularity (quasi-periodicity) of the sequence of the peaks and dips with respect to some rescaling functions of $z$. The same periodicity was found for the one-dimensional correlation function calculated for the sample of the ALSs under investigation. We assume the existence of a regular structure in the distribution of absorption matter, which is not only spatial but also temporal in nature with characteristic time varying within the interval 150--650 Myr for the cosmological model applied.

astro-ph↗

arXiv2006

Magnetars as cooling neutron stars with internal heating

We study thermal structure and evolution of magnetars as cooling neutron stars with a phenomenological heat source in a spherical internal layer. We explore the location of this layer as well as the heating rate that could explain high observable thermal luminosities of magnetars and would be consistent with the energy budget of neutron stars. We conclude that the heat source should be located in an outer magnetar's crust, at densities rho < 5e11 g/cm^3, and should have the heat intensity of the order of 1e20 erg/s/cm^3. Otherwise the heat energy is mainly emitted by neutrinos and cannot warm up the surface.

astro-ph↗