arXiv subjects

A. I. Bogomazov

Publications and source records attributed to A. I. Bogomazov.

At least 19 recordsLinked to original sources

arXiv2023

The evolution of relative frequencies of ONe and CO SNe Ia

In this population synthesis work we study a variety of possible origin channels of supernovae type Ia (SNe Ia) Among them mergers of carbon-oxygen (CO) and oxygen-neon (ONe) white dwarfs (WDs) under the influence of gravitational waves are considered as the primary channel of SNe Ia formation. We estimated frequencies of mergers of WDs with different chemical compositions and distributions of masses of merging WDs. We computed the dependence of the ratio of merger frequencies of ONe and CO WDs as primaries in corresponding binaries on time. The scatter of masses of considered sources (up to the factor $1.5-2$) of SNe Ia is important and should be carefully studied with other sophisticated methods from theoretical point of view. Our ``game of parameters'' potentially explains the increased dimming of SNe Ia in the redshift range $z\approx 0.5-1$ by the changes in the ratio of ONe and CO WDs, i.e., to describe the observed accelerated expansion of the Universe in terms of the evolution of properties of SNe Ia instead of cosmological explanations. This example shows the extreme importance of theoretical studies of problems concerning SNe Ia, because evolutionary scenario and parameter games in nature potentially lead to confusions in their empirical standardization and, therefore, they can influence on cosmological conclusions.

astro-ph.HE↗

arXiv2022

Population synthesis of AX J1745.6-2901 X-ray nova type binaries with rapidly decreasing orbital periods

The neutron star low mass X-ray binary (LMXB) AX J1745.6-2901 was detected an anomalously fast decrease of orbital period. The decreasing rate of orbital period exceeds the contribution of all processes extracting angular momentum from the binary star in standard model. Using SCENARIO MACHINE code we conducted a population synthesis study of X-ray novae with neutron stars to investigate a possible formation and evolution of such binaries. Such close LMXBs should experience a preceding common envelope stage, in which the magnetic fields of the low mass main-sequence donor stars can be dramatically amplified. Our calculations show that the magnetic stellar wind of the optical companion can efficiently extract angular momentum from the binary systems, and produce the observed orbital-period derivatives of AX J1745.6-2901 and black hole LMXBs. The estimated values of the required magnetic field induction are following: $B_\textrm{d}\approx 400$ G (AX~J1745.6-2901), $B_\textrm{d}\approx 1500$ G (KV UMa), $B_\textrm{d}\approx 400$ G (A0620-00), $B_\textrm{d}\approx 1800$ G (Nova Muscae). We successfully reproduced the current observational abundance of such anomalous neutron star X-ray novae, and computed the appropriate value of the parameter of magnetic braking $λ_\textrm{MSW}$ ($0.8-0.6$ for Roche lobe filling stars and $0.4-0.15$ for binaries with partial Roche lobe filling).

astro-ph.HE↗

arXiv2021

Parameters of X-ray binary system Scorpius X-1

We modelled optical light curves of Sco~X-1 obtained by the Kepler space telescope during K2 mission. Modelling was performed for the case of the strong heating of the optical star and accretion disc by X-rays. In the considered model the optical star fully filled its Roche lobe. We investigated the inverse problem in wide ranges of values of model parameters and estimated following parameters of Sco X-1: the mass ratio of components $q=M_x/M_v=3.6$ ($3.5-3.8$), where $M_x$ and $M_v$ were masses of the neutron and optical stars correspondingly, the orbital inclination was $i=30^{\circ}$ ($25^{\circ}-34^{\circ}$). In the brackets uncertainties of parameters $q$ and $i$ were shown, they originated due to uncertainties of characteristics of the physical model of Sco X-1. The temperature of non-heated optical star was $T_2 = 2500-3050$ K, its radius was $R_2=1.25R_{\odot}=8.7\times 10^{10}$ cm, and its bolometric luminosity was $L_{bol}=(2.1-4.6)\times 10^{32}$ erg s$^{-1}$. The mass of the star was $M_v\simeq 0.4M_{\odot}$. The contribution of the X-ray heated accretion disc dominated in the total optical emission of Sco~X-1. The transition between low and high states occurred due to the increase of X-ray luminosity by a factor $2-3$.

astro-ph.SR↗

arXiv2021

Gamma Ray Burst studies with THESEUS

Gamma-ray Bursts (GRBs) are the most powerful transients in the Universe, over-shining for a few seconds all other $γ$-ray sky sources. Their emission is produced within narrowly collimated relativistic jets launched after the core-collapse of massive stars or the merger of compact binaries. THESEUS will open a new window for the use of GRBs as cosmological tools by securing a statistically significant sample of high-$z$ GRBs, as well as by providing a large number of GRBs at low-intermediate redshifts extending the current samples to low luminosities. The wide energy band and unprecedented sensitivity of the Soft X-ray Imager (SXI) and X-Gamma rays Imaging Spectrometer (XGIS) instruments provide us a new route to unveil the nature of the prompt emission. For the first time, a full characterisation of the prompt emission spectrum from 0.3 keV to 10 MeV with unprecedented large count statistics will be possible revealing the signatures of synchrotron emission. SXI spectra, extending down to 0.3 keV, will constrain the local metal absorption and, for the brightest events, the progenitors' ejecta composition. Investigation of the nature of the internal energy dissipation mechanisms will be obtained through the systematic study with XGIS of the sub-second variability unexplored so far over such a wide energy range. THESEUS will follow the spectral evolution of the prompt emission down to the soft X-ray band during the early steep decay and through the plateau phase with the unique ability of extending above 10 keV the spectral study of these early afterglow emission phases.

astro-ph.IM↗

arXiv2019

Optical, J, and K light curves of XTE J1118+480 = KV UMa: the mass of the black hole and the spectrum of the non-stellar component

Optical, J, and K photometric observations of the KV UMa black hole X-ray nova in its quiescent state obtained in 2017-2018 are presented. A significant flickering within light curves was not detected, although the average brightness of the system faded by $\approx 0.1^m$ during 350 days. Changes in the average brightness were not accompanied with the increase or the decrease of the flickering. From the modelling of five light curves the inclination of the KV UMa orbit and the black hole mass were obtained: $i=74^{\circ}\pm 4^{\circ}$, $M_{BH}=(7.06÷7.24)M_{\odot}$ dependently on the used mass ratio. The non-stellar component of the spectrum in the range $λ=6400÷22000$Å can be fitted by a power law $F_λ\sim λ^α$, $α\approx -1.8$. The accretion disk orientation angle changed from one epoch to another. The model with spots on the star was inadequate. Evolutionary calculations using the "Scenario Machine" code were performed for low mass X-ray binaries, a recently discovered anomalously rapid decrease of the orbital period was taken into account. We showed that the observed decrease can be consistent with the magnetic stellar wind of the optical companion which magnetic field was increased during the common envelope stage. Several constraints on evolutionary scenario parameters were done.

astro-ph.HE↗

arXiv2018

Spin of LIGO/VIRGO merging black holes as the result of binary evolution

Recently discovered bursts of gravitational waves provide a good opportunity to verify the current view on the evolution of close binary stars. Modern population synthesis computer programs help to study this evolution from two main sequence stars up to the formation of compact remnants. To calculate the evolution of predecessors of black hole (BH) mergers we used the `Scenario Machine' code. The scenario modelling allowed to describe the evolution of systems for which the final stage is a BH+BH merger and showed the plausibility of modern evolutionary scenarios for binary stars and population synthesis models based on it. We discuss possible values of spins in BH mergers, and give arguments in favour of different values of spins of BH components in BH mergers (low spin + low spin, low spin + high spin, high spin + high spin). We predict that $\geq 50\%$ BH mergers originated through isolated binary evolution should possess spins of both BHs close to zero (low spin + low spin). Up to $\approx$10\% of BH mergers are able to consist of two BHs with spins close to one (high spin + high spin), predecessors of such binaries could be sources of two gamma ray bursts. The BH with the spin close to one could be formed as the result of the merger of two BHs formed via the collapse of a fast rotating star accompanied with a long gamma ray burst and/or a gravitational wave burst with smaller power in comparison with the merger of two BH remnants of binary components.

astro-ph.HE↗

arXiv2017

The evolution of the eccentricity in the eclipsing binary system AS Camelopardalis

In 2002, 2004, and 2017 we conducted high precision CCD photometry observations of the eclipsing binary system AS~Cam. By the analysis of the light curves from 1967 to 2017 (our data + data from the literature) we obtained photometric elements of the system and found the change of the system's orbital eccentricity by $Δe=0.03 \pm 0.01$. This change can indicate that there is a third companion in the system in a highly inclined orbit with respect to the orbital plane of the central binary, and its gravitational influence may cause the discrepancy between the observed and theoretical apsidal motion rates of AS~Cam.

astro-ph.SR↗

arXiv2017

Timing of AB And eclipses

This study aims timing the eclipses of the short period low mass binary star AB And. The times of minima are taken from the literature and from our observations in October 2013 (22 times of minima) and in August 2014 (23 times of minima). We find and discuss an inaccuracy in the determination of the types of minima in the previous investigation by \citet{li2014}. We study the secular evolution of the central binary's orbital period and the possibility of the existence of third and fourth companions in the system.

astro-ph.SR↗

arXiv2017

Wolf-Rayet stars, black holes and the first detected gravitational wave source

The recently discovered burst of gravitational waves GW150914 provides a good new chance to verify the current view on the evolution of close binary stars. Modern population synthesis codes help to study this evolution from two main sequence stars up to the formation of two final remnant degenerate dwarfs, neutron stars or black holes [Massevich 1988]. To study the evolution of the GW150914 predecessor we use the "Scenario Machine" code presented by [Lipunov 1996]. The scenario modelling conducted in this study allowed to describe the evolution of systems for which the final stage is a massive BH+BH merger. We find that the initial mass of the primary component can be $100÷140 M_{\odot}$ and the initial separation of the components can be $50÷350 R_{\odot}$. Our calculations show the plausibility of modern evolutionary scenarios for binary stars and the population synthesis modelling based on it.

astro-ph.HE↗

arXiv2016

Light equation in eclipsing binary CV Boo: third body candidate in elliptical orbit

A short period eclipsing binary star CV Boo is tested for the possible existence of additional bodies in the system with a help of the light equation method. We use data on the moments of minima from the literature as well as from our observations during 2014 May--July. A variation of the CV Boo's orbital period is found with a period of $\approx 75$ d. This variation can be explained by the influence of a third star with a mass of $\approx 0.4M_{\odot}$ in an eccentric orbit with $e\approx 0.9$. A possibility that the orbital period changes on long time scales is discussed. The suggested tertiary companion is near the chaotic zone around the central binary, so CV Boo represents an interesting example to test its dynamical evolution. A list of 14 minima moments of the binary obtained from our observations is presented.

astro-ph.SR↗

arXiv2016

A Study of the Evolution of the Close Binaries Cyg X-3, IC 10 X-1, NGC 300 X-1, SS 433, and M33 X-7 Using the "Scenario Machine"

Evolutionary tracks for the X-ray binaries Cyg X-3, IC 10 X-1, NGC 300 X-1, SS 433, and M33 X-7 are computed using the Scenario Machine code. The compact objects in IC 10 X-1, NGC 300 X-1, and M33 X-7 are the most massive stellar mass black hole candidates. Cyg X-3, IC 10 X-1, and NGC 300 X-1 are the only currently known Wolf-Rayet stars with degenerate companions. SS 433 is the only known superaccretor in the Milky Way. Therefore, the stars studied provide excellent laboratories for testing scenarios for the evolution of binaries under extreme conditions. The classical evolutionary scenario is consistent with modern observational data. During the evolution of these binaries, hypernova explosions accompanied by the collapse of stellar cores with large angular momenta can occur, leading to long gamma-ray bursts. At the end of their evolution, Cyg X-3, IC 10 X-1, NGC 300 X-1, and SS 433 may form binary relativistic objects, which will subsequently merge due to the radiation of gravitational waves. The gravitational waves emitted during mergers of relativistic stars should be detectable by existing and future gravitational-wave antennas. In the course of its future evolution, M33 X-7 will pass through a Thorne-Zytkow stage. The formation of a Thorne-Zytkow object can also be accompanied by gravitational-wave radiation. Figure 2 contains two merging black holes with masses almost identical to the second LIGO event GW151226.

astro-ph.HE↗

arXiv2015

An Exo-Jupiter Candidate in the Eclipsing Binary FL Lyr

Light curves of the eclipsing binary FL Lyr acquired by the Kepler space telescope are analyzed. Eclipse timing measurements for FL Lyr testify to the presence of a third body in the system. Preliminary estimates of its mass and orbital period are > 4M_Jupiter and > 7 yrs. The times of primary minimum in the light curve of FL Lyr during the operation of the Kepler mission are presented.

astro-ph.SR↗

arXiv2015

Timing of eclipsing binary V0873 Per: a third body candidate

We analyse a set of moments of minima of eclipsing variable V0873 Per. V0873 Per is a short period low mass binary star. Data about moments of minima of V0873 Per were taken from literature and our observations during 2013-2014. Our aim is to test the system on existence of new bodies using timing of minima of eclipses. We found the periodical variation of orbital period of V0873 Per. This variation can be explained by the gravitational influence of a third companion on the central binary star. The mass of third body candidate is $\approx 0.2 M_{\odot}$, its orbital period is $\approx 300$ days. The paper also includes a table with moments of minima calculated from our observations which can be used in future investigations of V0873 Per.

astro-ph.SR↗

arXiv2013

INTEGRAL observations of SS433: system's parameters and nutation of supercritical accretion disk

Based on multiyear INTEGRAL observations of SS433 in 2003-2011, a composite IBIS/ISGRI 18-60 keV orbital light curve is constructed around zero precessional phases psi_{pr}= 0 at the maximim accretion disk opening angle. It shows a peculiar shape with significant excess near the orbital phase phi_orb= 0.25, which is not seen in the softer 2-10 keV energy band. The 40-60 keV orbital light curve demonstrates two almost equal humps at phases \sim 0.25 and \sim 0.75, most likely due to nutation effects of the accretion disk. The nutational variability of SS433 in 15-50 keV with a period of 6.290 days is independently found from timing analysis of Swift/BAT data. The change of the off-eclipse 18-60 keV X-ray flux with the precessional phase shows a double-wave form with strong primary maximum at psi_{pr}= 0 and weak but significant secondary maximum at psi_{pr}= 0.6. A weak variability of the 18-60 keV flux in the middle of the orbital eclipse correlated with the disk precessional phase is also observed. The joint analysis of the broadband 18-60 keV orbital and precessional light curves confirms the presence of a hot extended corona in the central parts of the supercritical accretion disk and constrains the binary mass ratio in SS433 in the range 0.5>q>0.3, suggesting the black hole nature of the compact object.

astro-ph.HE↗

arXiv2011

Type Ia Supernovae: Non-standard Candles of the Universe

We analyze the influence of the evolution of light absorption by gray dust in the host galaxies of type Ia supernovae (SNe Ia) and the evolution of the mean combined mass of close-binary carbon-oxygen white dwarfs merging due to gravitational waves (SNe Ia precursors) on the interpretation of Hubble diagrams for SNe Ia. A significant increase in the mean SNe Ia energy due to the higher combined masses of merging dwarfs should be observable at redshifts z > 2. The observed relation between the distance moduli and redshifts of SNe Ia can be interpreted not only as evidence for accelerated expansion of the Universe, but also as indicating time variations of the gray-dust absorption of light from these supernovae in various types of host galaxies, observational selection effects, and the decrease in mean combined masses of merging degenerate dwarfs.

astro-ph.SR↗

arXiv2011

Supernovae type Ia: non-standard candles of the Universe

We analyze the influence of the evolution of light absorbtion by grey dust in SNe Ia host galaxies and the influence of the evolution of average total mass of coalescing double carbon-oxygen white dwarfs (progenitors of SNe Ia) under the influence of gravitational radiation on the interpretation of Hubble diagrams of SNe Ia. Significant increase in the average energy of SNe Ia due to increase in the total mass of merging dwarfs can be observed at red shift z> 2. The observed dependence of the distance modulus from the red shift in observations of SNe Ia can be explained not only by the assumption about accelerated expansion of the Universe, but also by the evolution of the absorbtion of light by grey dust in various types of host galaxies of SNe Ia, by the effects of observational selection and by the decrease in the average mass of coalescing degenerate dwarfs.

astro-ph.SR↗

arXiv2009

Population synthesis of gamma-ray bursts with precursor activity and the spinar paradigm

We study statistical properties of long gamma-ray bursts (GRBs) produced by the collapsing cores of WR stars in binary systems. Fast rotation of the cores enables a two-stage collapse scenario, implying the formation of a spinar-like object. A burst produced by such a collapse consists of two pulses, whose energy budget is enough to explain observed GRBs. We calculate models of spinar evolution using results from a population synthesis of binary systems (done by the `Scenario Machine') as initial parameters for the rotating massive cores. Among the resulting bursts, events with the weaker first peak, namely, precursor, are identified, and the precursor-to-main-pulse time separations fully agree with the range of the observed values. The calculated fraction of long GRBs with precursor (about 10 per cent of the total number of long GRBs) and the durations of the main pulses are also consistent with observations. Precursors with lead times greater by up to one order of magnitude than those observed so far are expected to be about twice less numerous. Independently of a GRB model assumed, we predict the existence of precursors that arrive up to >~ 10^3 s in advance of the main events of GRBs.

astro-ph.HE↗

arXiv2009

The Mass of the Black Hole in the X-ray Binary M33 X-7 and the Evolutionary Status of M33 X-7 and IC 10 X-1

We have analyzed the observed radial-velocity curve for the X-ray binary M33 X-7 in a Roche model. We have analyzed the dependence between the component masses and the degree of filling of the optical star's Roche lobe to obtain the ratio of the masses of the optical star and compact object. For the most probable mass of the optical star, $m_v=70M_{\odot}$, the mass of the compact object is $m_x=15.55\pm3.20 M_{\odot}$. It has been shown that black holes with masses of $m_x=15M_{\odot}$ and even higher can form in binaries. We present characteristic evolutionary tracks for binary systems passing through an evolutionary stage with properties similar to M33 X-7 - type objects. According to population-synthesis analyses, such binaries should be present in galaxies with masses of at least $10^{11}M_{\odot}$. The present number of such systems in M33 should be of the order of unity. We have also studied the evolutionary status of the X-ray binary IC 10 X-1 with a Wolf-Rayet component, which may contain a massive black hole. The final stages of the evolution of the M33 X-7 and IC 10 X-1 systems should be accompanied by the radiation of gravitational waves.

astro-ph.SR↗