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Near-periodical spin period evolution in the binary system LMC X-4
Monthly Notices of the Royal Astronomical Society. 2017. Vol. 464. No. 2. P. 2039–2045.
Lutovinov A.
In this paper, we investigated the long-term evolution of the pulse period in the high-mass X-ray binary LMC X-4 by taking advantage of more than 43 yr of measurements in the X-ray domain. Our analysis revealed for the first time that the source is displaying near-periodical variations of its spin period on a time-scale of roughly 6.8 yr, making LMC X-4 one of the known binary systems showing remarkable long-term spin torque reversals. We discuss different scenarios to interpret the origin of these torque reversals.
Biryukov A., Abolmasov P., Monthly Notices of the Royal Astronomical Society 2021 Vol. 505 No. 2 P. 1775–1786
The rotation of a magnetized accreting neutron star (NS) in a binary system is described by its spin period and two angles: spin inclination α with respect to the orbital momentum and magnetic angle χ between the spin and the magnetic moment. Magnetospheric accretion spins the NS up and adjusts its rotation axis, decreasing α ...
Added: October 31, 2022
Gorban A., Мольков С. В., Цыганков С. С. et al., Письма в Астрономический журнал 2022 Т. 48 № 4 С. 279–289
The results of the broadband spectral and timing study of the transient X-ray pulsar GRO J2058+42 in a wide energy range at a low luminosity Lx ≃ 2.5 × 10^36 erg s^−1 are reported. The data revealed that the pulse profile and pulse fraction of the source are significantly changed in comparison with previous NuSTAR ...
Added: June 16, 2022
Gorban A., Мольков С. В., Цыганков С. С. et al., Письма в Астрономический журнал 2021 Т. 47 № 6 С. 416–427
We present the results of our spectral and timing analysis of the emission from the transient X-ray pulsar XTE J1946+274 based on the simultaneous NuSTAR and Swift/XRT observations in the broad energy range 0.3–79 keV carried out in June 2018 during a bright outburst. Our spectral analysis has confirmed the presence of a cyclotron absorption ...
Added: November 18, 2021
Sazonov S., Kulkarni S., Monthly Notices of the Royal Astronomical Society 2021 Vol. 508 No. 3 P. 3820–3847
We present the first sample of tidal disruption events (TDEs) discovered during the SRG all-sky survey. These 13 events were selected among X-ray transients detected in the 0° < l < 180° hemisphere by eROSITA during its second sky survey (2020 June 10 to December 14) and confirmed by optical follow-up observations. The most distant ...
Added: October 27, 2021
Sazonov S., New Astronomy Reviews 2020 Vol. 88 P. 101536
Seventeen years of hard X-ray observations with the instruments of the INTEGRAL observatory, with a focus on the Milky Way and in particular on the Galactic Centre region, have provided a unique database for exploration of the Galactic population of low-mass X-ray binaries (LMXBs). Our understanding of the diverse energetic phenomena associated with accretion of ...
Added: November 16, 2020
Sazonov S., Monthly Notices of the Royal Astronomical Society 2019 Vol. 489 No. 1 P. 1127–1138
There is a hope that looking into the early Universe with next-generation telescopes, one will be able to observe the early accretion growth of supermassive black holes (BHs) when their masses were ∼104-106 M☉. According to the standard accretion theory, the bulk of the gravitational potential energy released by radiatively efficient accretion of matter on to ...
Added: August 6, 2020
Lutovinov A., Monthly Notices of the Royal Astronomical Society 2019 Vol. 482 No. 1 P. 1392–1405
We report a discovery of low-frequency quasi-periodic oscillation at 0.3-0.7 Hz in the power spectra of the accreting black hole GRS 1739-278 in the hard-intermediate state during its 2014 outburst based on the NuSTAR and Swift/XRT data. The QPO frequency strongly evolved with the source flux during the NuSTAR observation. The source spectrum became softer ...
Added: February 7, 2019
Lutovinov A., Monthly Notices of the Royal Astronomical Society: Letters 2018 Vol. 479 No. 1 P. L134–L138
We report on the monitoring of the final stage of the outburst from the first Galactic ultraluminous X-ray pulsar Swift J0243.6+6124, which reached ˜40 Eddington luminosities. The main aim of the monitoring program with the Swift/XRT telescope was to measure the magnetic field of the neutron star using the luminosity of transition to the `propeller' ...
Added: November 1, 2018
Lipunova G. V., Malanchev K., Shakura N. I., , in: Accretion Flows in Astrophysics.: Springer International Publishing, 2018. Ch. 1 P. 1–106.
Accretion discs are powerful energy factories in our Universe. They effectively transform the potential energy of gravitational interaction to emission, thereby unraveling the physics of distant objects. This is possible due to the presence of viscosity, driven by turbulent motions in accretion discs. In this chapter, we describe the equations for disc accretion in the ...
Added: October 26, 2018
Shakura N. I., Lipunova G. V., Malanchev K. et al., Springer International Publishing, 2018.
This book highlights selected topics of standard and modern theory of accretion onto black holes and magnetized neutron stars. The structure of stationary standard discs and non-stationary viscous processes in accretion discs are discussed to the highest degree of accuracy analytic theory can provide, including relativistic effects in flat and warped discs around black holes. ...
Added: October 26, 2018
Oknyansky V., Malanchev Konstantin L., Gaskell C. M., , in: Revisiting narrow-line Seyfert 1 galaxies and their place in the Universe (NLS1-2018), 9-13 April 2018, Padova Botanical Garden, ItalyIssue 328: Proceedings of Science.: Trieste: Scuola Internazionale Superiore di Studi Avanzati (SISSA), 2018. Ch. 12 P. 1–6.
Two major challenges to unification schemes for active galactic nuclei (AGN) activity are the existence of Narrow-Line Seyfert 1s (NLS1s) and the existence of changing-look (CL) AGNs. AGNs can drastically change their spectral appearance in the optical (changing their Seyfert type) and/or in the X-ray region. We illustrate the CL phenomenon with our multi-wavelength monitoring ...
Added: October 26, 2018
Malanchev K., Journal of Physics: Conference Series 2016 Vol. 675 No. 3 P. 1–4
We describe phenomenon of X-ray Novae in a model of non-stationary accretion α-disk with account for irradiation and vertical convection in outer disk region. We extended the commonly used disk vertical structure model by adding viscous turbulent energy generation in mixing length theory. This model was used to simulate both optical and X-ray light curves ...
Added: February 1, 2018
Wijnands R., Tsygankov S., Degenaar N. et al., Monthly Notices of the Royal Astronomical Society 2017 Vol. 470 No. 1 P. 126–141
Observations of accreting neutron stars (NSs) with strong magnetic fields can be used not only for studying the accretion flow interaction with the NS magnetospheres, but also for understanding the physical processes inside NSs and for estimating their fundamental parameters. Of particular interest are (I) the interaction of a rotating NS (magnetosphere) with the infalling ...
Added: January 16, 2018
Lutovinov A., Astronomy and Astrophysics 2017 Vol. 605 P. А39/1–А39/8
Aims: The magnetic field of accreting neutron stars determines their overall behavior including the maximum possible luminosity. Some models require an above-average magnetic field strength (≳1013 G) in order to explain super-Eddington mass accretion rate in the recently discovered class of pulsating ultraluminous X-ray sources (ULX). The peak luminosity of SMC X-3 during its major ...
Added: January 16, 2018
Lutovinov A., Monthly Notices of the Royal Astronomical Society 2017 Vol. 466 No. 1 P. 593–599
We report on the first focused hard X-ray view of the absorbed supergiant system IGR J18027-2016 performed with the Nuclear Spectroscopic Telescope Array observatory. The pulsations are clearly detected with a period of Pspin = 139.866(1) s and a pulse fraction of about 50-60 per cent at energies from 3 to 80 keV. The source ...
Added: January 16, 2018
Lutovinov A., Monthly Notices of the Royal Astronomical Society 2016 Vol. 462 No. 4 P. 3823–3829
We report the results of a comprehensive analysis of X-ray (Chandra and Swift observatories), optical (Southern African Large Telescope, SALT) and near-infrared (the VVV survey) observations of the Be/X-ray binary pulsar 2S 1553-542. Accurate coordinates for the X-ray source are determined and are used to identify the faint optical/infrared counterpart for the first time. Using ...
Added: January 16, 2018
Lutovinov A., Astronomy and Astrophysics 2016 Vol. 593 P. A16/1–A16/7
Aims: We present the results of the monitoring programmes performed with the Swift/XRT telescope and aimed specifically to detect an abrupt decrease of the observed flux associated with a transition to the propeller regime in two well-known X-ray pulsars 4U 0115+63 and V 0332+53.
Methods: Both sources form binary systems with Be optical companions and undergo ...
Added: January 16, 2018
Lutovinov A., Monthly Notices of the Royal Astronomical Society 2016 Vol. 457 No. 1 P. 258–266
We report the results of a spectral and timing analysis of the poorly studied transient X-ray pulsar 2S 1553-542 using data collected with the NuSTAR and Chandra observatories and the Fermi/GBM instrument during an outburst in 2015. The properties of the source at high energies (>30 keV) are studied for the first time and the ...
Added: January 16, 2018
Malanchev K. L., Postnov K. A., Shakura N. I., Monthly Notices of the Royal Astronomical Society 2017 P. 410–417
The vertical structure of stationary thin accretion discs is calculated from the energy balance equation with heat generation due to microscopic ion viscosity η and electron heat conductivity κ, both depending on temperature. In the optically thin discs it is found that for the heat conductivity increasing with temperature, the vertical temperature gradient exceeds the ...
Added: October 30, 2017
Lipunova G. V., Malanchev K. L., Monthly Notices of the Royal Astronomical Society 2017 Vol. 468 No. 4 P. 4735–4747
We investigate the viscous evolution of the accretion disc in 4U 1543-47, a black hole binary system, during the first 30 d after the peak of the 2002 burst by comparing the observed and theoretical accretion rate evolution \dot{M}(t). The observed \dot{M}(t) is obtained from spectral modelling of the archival Proportional Counter Array aboard the ...
Added: October 30, 2017
Siparov S., Samodurov V., Laptev G., Astronomy and Astrophysics 2015 Vol. 574 No. L2 P. 1–4
Many astrophysical sources that emit narrow radio-frequency spectral lines are believed to be sets of molecular condensation, each of which works as a maser, so that the whole set produces a characteristic spectrum. The forms of these spectra vary with time on various time-scales from months to dozens of minutes. We analysed the ultra-short variations ...
Added: March 4, 2015