В. Ф. Сулейманов
A5007375724- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- High-pressure geophysics and materials
- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Astronomical Observations and Instrumentation
- Mechanics and Biomechanics Studies
- Astrophysics and Star Formation Studies
- Geophysics and Sensor Technology
- Solar and Space Plasma Dynamics
- Astronomy and Astrophysical Research
- Geophysics and Gravity Measurements
- Astro and Planetary Science
- Galaxies: Formation, Evolution, Phenomena
- Atomic and Subatomic Physics Research
- Nuclear Physics and Applications
- Advanced X-ray Imaging Techniques
- Scientific Measurement and Uncertainty Evaluation
- History and Developments in Astronomy
- Particle Accelerators and Free-Electron Lasers
- Medical Imaging Techniques and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- earthquake and tectonic studies
- NMR spectroscopy and applications
University of Tübingen
2015-2024
Kazan Federal University
2013-2022
Max Planck Institute for Astrophysics
2010-2022
Space Research Institute
2011-2022
Russian Academy of Sciences
1998-2020
China Academy of Space Technology
2016
University of Geneva
2016
University of Oulu
2005-2011
Pennsylvania State University
2011
Peter the Great St. Petersburg Polytechnic University
2011
We study properties of luminous X-ray pulsars using a simplified model the accretion column. The maximal possible luminosity is calculated as function neutron star (NS) magnetic field and spin period. It shown that can reach values order 1040 erg s−1 for magnetar-like (B ≳ 1014 G) long periods (P 1.5 s). relative narrowness an area feasible NS parameters which are able to provide higher luminosities leads conclusion L ≃ good estimate limiting NS. Because this coincides with cut-off observed...
Abstract We present volume-limited samples of cataclysmic variables (CVs) and AM CVn binaries jointly selected from SRG/eROSITA eRASS1 Gaia DR3 using an X-ray + optical color–color diagram (the “X-ray Main Sequence”). This tool identifies all CV subtypes, including magnetic low-accretion rate systems, in contrast to most previous surveys. find 23 CVs, 3 which are CVns, out 150 pc the Western Galactic Hemisphere. Our sample is spectroscopically verified complete down L X = 1.3 × 10 29 erg s...
The accretion flow around X-ray pulsars with a strong magnetic field is funnelled by the to relatively small regions close poles of neutron star (NS), hotspots. During outbursts regularly observed from some pulsars, luminosity can be so high, that emerging radiation able stop accreting matter above surface via radiation-dominated shock, and column begins rise. This border usually called "critical luminosity". Here we calculate critical as function NS strength $B$ using exact Compton...
We present here the first convincing observational manifestation of a magnetar-like magnetic field in an accreting neutron star binary system – pulsating ultraluminous X-ray source X−2 galaxy M82. Using Chandra observatory data, we show that exhibit bimodal distribution luminosity with two well-defined peaks separated by factor 40. This behaviour can be interpreted as action 'propeller regime' accretion. The onset propeller 1.37 s pulsar at ∼1040 erg s−1 implies dipole component ∼1014 G.
Thermal emission during X-ray bursts is a powerful tool to determine neutron star masses and radii, if the Eddington flux apparent radius in cooling tail can be measured accurately, distances sources are known. We propose here an improved method of determining basic stellar parameters using data from phase photospheric expansion covering large range luminosities. Because at that blackbody depends only on spectral hardening factor (color-correction), we suggest fit theoretical dependences...
Magnetized neutron stars power at least some ultraluminous X-ray sources. The accretion flow in these cases is interrupted the magnetospheric radius and then reaches surface of a star following magnetic field lines. Accreting matter moving along lines forms envelope around central object. We show that case high-mass rates ≳ 1019 g s−1 becomes closed optically thick, which influences dynamics observational manifestation hidden behind envelope. Particularly, thick results multi-colour...
The cooling phase of thermonuclear (type-I) X-ray bursts can be used to constrain the neutron star (NS) compactness by comparing observed tracks accurate theoretical atmosphere model calculations. By applying so-called tail method, where information from whole track is used, we mass, radius, and distance for three different NSs in low-mass binaries 4U 1702-429, 1724-307, SAX J1810.8-260. Care taken only use hard state it thought that NS surface alone emitting. We then utilize a Markov chain...
Observations of thermonuclear X-ray bursts from accreting neutron stars (NSs) in low-mass binary systems can be used to constrain NS masses and radii. Most previous work this type has set these constraints using Planck function fits as a proxy: both the models data are fit with diluted blackbody functions yield normalizations temperatures which then compared against each other. Here, for first time, we atmosphere bursting NSs directly observed spectra. We present hierarchical Bayesian...
Abstract A large energy-dependent X-ray polarization degree is detected by the Imaging Polarimetry Explorer (IXPE) in high-soft emission state of black hole binary 4U 1630–47. The highly significant detection (at ≈50 σ confidence level) an unexpectedly high polarization, rising from ∼6% at 2 keV to ∼10% 8 keV, cannot be easily reconciled with standard models thin accretion disks. In this work, we compare predictions different theoretical IXPE data and conclude that observed properties are...
Aims. X-ray bursting neutron stars in low-mass binaries constitute an appropriate source class for constraining the masses and radii of stars, but a sufficiently extended set corresponding model atmospheres is necessary these investigations.
Spectral measurements of thermonuclear (type I) X-ray bursts from low-mass binaries have been used to measure neutron star (NS) masses and radii. A number systematic issues affect such raised concerns as the robustness methods. We present analysis emission observed 4U 1608−52 at various persistent fluxes. find a strong dependence burst properties on flux spectral hardness before burst. Bursts occurring during low accretion rate (hard) state exhibit evolution blackbody normalization...
We present the results of monitoring programmes performed with Swift/XRT telescope and aimed specifically to detect an abrupt decrease observed flux associated a transition propeller regime in two well known X-ray pulsars 4U 0115+63 V 0332+53 during their giant outbursts 2015. Such transitions were detected at threshold luminosities $(1.4\pm0.4)\times10^{36}$ erg s$^{-1}$ $(2.0\pm0.4)\times10^{36}$ for 0332+53, respectively. Spectra sources are shown be significantly softer low state. In...
Context: Central Compact Objects (CCOs) in supernova remnants are isolated thermally emitting neutron stars (NSs). They most probably characterized by a magnetic field strength that is roughly two orders of magnitude lower than the radio and accreting pulsars. The thermal emission CCOs can be modeled to obtain constraints on physical parameters star such as its mass, radius, effective temperature, chemical composition. Aims: CCO HESS, J1731-347 one brightest objects this class. We present...
Cyclotron resonance scattering features observed in the spectra of some X-ray pulsars show significant changes line energy with pulsar luminosity. At high luminosities, these variations are often associated onset and growth accretion column, which is believed to be origin emission cyclotron lines. However, this scenario inevitably implies large gradient magnetic field strength within line-forming region, makes formation line-like problematic. Moreover, variation much smaller than could...
We report on the analysis of NuSTAR observations Be-transient X-ray pulsar V 0332+53 during giant outburst in 2015 and another minor 2016. confirm cyclotron-line energy-luminosity correlation previously reported source line energy decrease outburst. Based 2016 observations, we find that a year later has increased again essentially reaching pre-outburst values. discuss this behaviour conclude it is likely caused by change emission region geometry rather than suggested accretion-induced decay...
The hardness of the X-ray spectra intermediate polars (IPs) is determined mainly by white dwarf (WD) compactness (mass-radius ratio, M/R) and, thus, hard can be used to constrain WD mass. An accurate mass estimate requires finite size magnetosphere R_m taken into account. We suggested derive it either directly from observed break frequency in power spectrum or optical lightcurves a polar, assuming corotation. Here we apply this method all IPs NuSTAR (10 objects) and Swift/BAT (35 objects)....
Cen X-3 is the first X-ray pulsar discovered 50 years ago. Radiation from such objects expected to be highly polarized due birefringence of plasma and vacuum associated with propagation photons in presence strong magnetic field. Here we present results observations performed Imaging Polarimetry Explorer. The source exhibited significant flux variability was observed two states different by a factor ~20 flux. In low-luminosity state no polarization found either pulse phase-averaged (with...
X-ray polarimetry is a unique way to probe the geometrical configuration of highly magnetized accreting neutron stars (X-ray pulsars). GRO J1008−57 first transient pulsar observed at two different flux levels by Imaging Polarimetry Explorer (IXPE) during its outburst in November 2022. We find polarization properties be independent luminosity, with degree varying between nondetection and about 15% over pulse phase. Fitting phase-resolved spectro-polarimetric data rotating vector model allowed...
Abstract The Imaging X-ray Polarimetry Explorer (IXPE) observed the black hole binary 4U 1630–47 in steep power-law (or very high) state. observations reveal a linear polarization degree of 2–8 keV X-rays 6.8% ± 0.2% at position angle 21.°3 0.°9 east north (all errors 1 σ confidence level). Whereas increases with energy, stays constant within accuracy our measurements. We compare source state previous IXPE measurement high soft find that, even though flux and spectral shape are significantly...
We present the first X-ray spectropolarimetric results for Cygnus X-1 in its soft state from a campaign of five IXPE observations conducted during 2023 May-June. Companion multiwavelength data are likewise shown. The 2-8 keV X-rays exhibit net polarization degree PD=1.99%+/-0.13% (68% confidence). signal is found to increase with energy across IXPE's bandpass. polarized an energy-independent angle PA=-25.7+/-1.8 deg. East North This consistent being aligned Cyg X-1's AU-scale compact radio...
ABSTRACT Pulse profile modelling (PPM) is a comprehensive relativistic ray-tracing technique employed to determine the properties of neutron stars. In this study, we apply Type I X-ray burster and accretion-powered millisecond pulsar XTE J1814−338, extracting its fundamental using PPM thermonuclear burst oscillations. Using data from 2003 outburst, single uniform temperature hotspot model, infer J1814−338 be located at distance $7.2^{+0.3}_{-0.4}$ kpc, with mass $1.21^{+0.05}_{-0.05}$...
We present results of an analysis broadband X-ray spectra 14 intermediate polars obtained with the RXTE observatory (PCA and HEXTE spectrometers, 3–100 keV). For this we have calculated theoretical models structure emergent spectrum post-shock region polars. By fitting model to observed derive estimates for masses white dwarfs. compare resulting by other authors methods. The us are smaller than using PCA GINGA data, they in good agreement derived from radial velocity studies.