A5057621814- Astrophysical Phenomena and Observations
- Mechanics and Biomechanics Studies
- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Geophysics and Gravity Measurements
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Astronomical Observations and Instrumentation
- Galaxies: Formation, Evolution, Phenomena
- Scientific Measurement and Uncertainty Evaluation
- Particle Accelerators and Free-Electron Lasers
- Black Holes and Theoretical Physics
- High-pressure geophysics and materials
- Particle Detector Development and Performance
- Superconducting Materials and Applications
- Adaptive optics and wavefront sensing
- Heat Transfer Mechanisms
- Ionosphere and magnetosphere dynamics
- Relativity and Gravitational Theory
- Crystallography and Radiation Phenomena
- Dark Matter and Cosmic Phenomena
- Molecular Spectroscopy and Structure
- Particle physics theoretical and experimental studies
Czech Academy of Sciences, Astronomical Institute
2015-2024
Roma Tre University
2022
Astronomical Institute of the Slovak Academy of Sciences
2018
Czech Academy of Sciences
2013
University of Cologne
2013
Charles University
2003-2004
University of Leicester
2004
Chalmers University of Technology
2003
This White Paper, submitted to the recent ESA call for science themes define its future large missions, advocates need a transformational leap in our understanding of two key questions astrophysics: 1) How does ordinary matter assemble into scale structures that we see today? 2) do black holes grow and shape Universe? Hot gas clusters, groups intergalactic medium dominates baryonic content local Universe. To understand astrophysical processes responsible formation assembly these structures,...
We report on a scheme for incorporating vertical radiative energy transport into fully relativistic, Kerr-metric model of optically thick, advective, transonic alpha disks. Our code couples the radial and equations accretion disk. The flux was computed in diffusion approximation, convection is included mixing-length approximation. present detailed structure this "two-dimensional" slim-disk alpha=0.01. then calculated emergent spectra integrated over disk surface. values surface density,...
eXTP is a science mission designed to study the state of matter under extreme conditions density, gravity and magnetism. Primary goals are determination equation at supra-nuclear measurement QED effects in highly magnetized star, accretion strong-field regime gravity. targets include isolated binary neutron stars, strong magnetic field systems like magnetars, stellar-mass supermassive black holes. The carries unique unprecedented suite state-of-the-art scientific instruments enabling for...
Abstract The size and geometry of the X-ray-emitting corona in an active galactic nucleus (AGN) are still not well constrained. Dovčiak & Done proposed a method based on calculations assuming point-like lamp-post corona. To perform more self-consistent energy spectra extended coronae, we develop monk , Monte Carlo radiative transfer code dedicated to Comptonized Kerr spacetime. In assume Klein–Nishina scattering cross section include all general relativistic effects. We find that for...
We find evidence that the two high frequency QPOs in Sco X-1 are, more often than not, approximately 2:3 ratio familiar from studies of black hole candidates (e.g., XTE J1550-564, Remillard et al. [CITE]). This implies double kHz QPO phenomenon neutron stars has its origin properties strong-field gravity and little to do with rotation a stellar surface or any magnetic field structure anchored star.
Slim-disk models describe advective accretion flows at high luminosities, while reducing to the standard thin disk form in low luminosity limit. We have developed a new spectral model, slimbb, within framework of XSPEC, which describes fully relativistic slim-disk and includes photon ray-tracing that starts from photosphere, rather than equatorial plane. demonstrate features this model by applying it RXTE spectra persistent black-hole X-ray binary LMC X-3. X-3 has virtues exhibiting large...
We analyse and report in detail new near-infrared (1.45 - 2.45 microns) observations of the Dusty S-cluster Object (DSO/G2) during its approach to black hole at center Galaxy that were carried out with ESO VLT/SINFONI between February September 2014. Before May 2014 we detect spatially compact Br-gamma Pa-alpha line emission from DSO about 40mas east SgrA*. The velocity source, measured red-shifted emission, is 2700+-60 km/s. No blue-shifted above noise level detected position SgrA* or...
Abstract X-ray polarization is a powerful tool to investigate the geometry of accreting material around black holes, allowing independent measurements hole spin and orientation innermost parts accretion disk. We perform spectropolarimetric analysis an binary system in Large Magellanic Cloud, LMC X-3, that hosts stellar-mass hole, known be persistently since its discovery. report first detection X-3 with Imaging Polarimetry Explorer, find average degree (PD) 3.2% ± 0.6% constant angle −42° 6°...
We show that a luminous torus in the Schwarzschild metric oscillating along its own axis gives rise to periodically varying flux of radiation, even though source radiation is steady and perfectly axisymmetric.This implies simplest oscillation mode an accretion flow, axisymmetric up-and-down motion at meridional epicyclic frequency, may be directly observable when it occurs inner parts flow around neutron stars black holes.The high-frequency modulations X-ray observed low-mass binaries two...
We present a statistical analysis of polarized near-infrared (NIR) light from Sgr A*, the radio source associated with supermassive black hole at center Milky Way. The observations have been carried out using adaptive optics instrument NACO VLT UT4 in infrared $K_\mathrm{s}$-band 2004 to 2012. Several flux excursions were observed during these years. Linear polarization 2.2 $\mu m$, its statistics and time variation, can be used constrain physical conditions accretion process onto this hole....
We propose the development of X-ray interferometry (XRI), to reveal universe at high energies with ultra-high spatial resolution. With baselines which can be accommodated on a single spacecraft, XRI reach 100 $\mu$as resolution 10 \AA (1.2 keV) and 20 2 (6 keV), enabling imaging imaging-spectroscopy (for example) coronae nearby accreting supermassive black holes (SMBH) SMBH `shadow'; accretion flows outflows; binary winds orbits; stellar within ~100 pc many exoplanets transit across them....
ABSTRACT Measurements of the angular momentum (spin) astrophysical black holes are extremely important, as they provide information on hole formation and evolution. We present simulated observations an X-ray binary system with Imaging Polarimetry Explorer (IXPE), aim to study robustness spin geometry measurements using polarimetry. As a representative example, we used parameters GRS 1915+105 in its former unobscured, soft state. In order simulate polarization properties, modelled source...
We study the process of spinning up black holes by accretion from slim disks in a wide range rates. show that for super-Eddington rates and low values viscosity parameter alpha (\lesssim 0.01) limiting value dimensionless spin a_* can reach higher than a_*=0.9978 inferred Thorne (1974) his seminal study. For \mdot=10\mdot_{Edd} alpha=0.01 equilibrium is reached at a_*=0.9994. depends strongly on assumed alpha. also prove high impact captured radiation evolution negligible.
Abstract We develop a Monte Carlo code to compute the Compton-scattered X-ray flux arising from hot inner flow that undergoes Lense–Thirring precession. The intercepts seed photons an outer truncated thin disk. A fraction of Comptonized will illuminate disk, and reflected/reprocessed contribute observed spectrum. total spectrum, including disk thermal emission, Comptonization, reflection, is modeled within framework general relativity, taking light bending gravitational redshift into...
Accretion disks around stellar-mass black holes (BHs) emit radiation peaking in the soft X-rays when source is thermal state. The emerging photons are polarized and, for symmetry reasons, polarization integrated over expected to be either parallel or perpendicular (projected) disk axis, because of electron scattering disk. However, due General Relativity effects photon vectors will rotate with respect their original orientation, by an amount depending on both BH spin and observer's...
ABSTRACT We present the results from an X-ray variability study of IRAS 13224-3809. This is probably best source for reverberation studies since it bright, extremely variable, and has been extensively observed with XMM–Newton. used all archival XMM–Newton data three EPIC cameras (to increase signal to noise) and, given many observations source, we were able compute time lags spectra in different flux levels/periods. fitted energy spectra, simultaneously, using a new code that computes...
We give an overview of the science objectives and mission design Spectroscopic Time-Resolving Observatory for Broadband Energy X-rays (STROBE-X) observatory, which has been proposed as a NASA probe-class (~$1.5B) in response to Astro2020 recommendation X-ray probe.
We present the first results obtained by application of KYNREFREV-reverberation model, which is ready for its use in XSPEC. This model computes time dependent reflection spectra disc as a response to flash primary power-law radiation from point source corona located on axis black hole accretion (lamp-post geometry). Full relativistic effects are taken into account. The ionisation set each radius according amount incident flux and density disc. tested fitting predictions observed time-lag...
We address a question whether the observed light curves of X-ray flares originating deep in galactic cores can give us independent constraints on mass central supermassive black hole. To this end, we study four brightest which have been recorded from Sagittarius A*. They all exhibit an asymmetric shape consistent with combination two intrinsically separate peaks occur at certain time delay respect to each other, and are characterized by their mutual flux ratio profile raising/declining...
The continuum-fitting method is one of the two most advanced methods determining black hole spin in accreting X-ray binary systems. There are, however, still some unresolved issues with underlying disk models. One them manifests as an apparent decrease for increasing source luminosity. Here, we perform a few simple tests to establish whether outflows from close inner radius can address this problem. We employ four different parametric models describe wind and compare these luminosity...
The Spectroscopic Time-Resolving Observatory for Broadband X-rays (STROBE-X) is a proposed NASA Astrophysics Probe-class mission. STROBE-X time domain and multi-messenger mission designed to provide an unparalleled laboratory probing strong gravity the behavior of matter in extreme environments. instrument suite encompasses wide-field monitor two pointed instruments transient discovery capability rapid follow-up with broadband (0.2–30 keV), high resolution spectroscopy. Over 10,000...
Reprocessing of primary X-ray emission in the accretion disk black hole binaries (BHXRBs) produces reflection spectrum, with characteristic Fe K$\alpha$ fluorescence line. Strong low frequency quasi-periodic oscillations (QPOs) are observed from BHXRBs, and dependence QPO properties (e.g., phase-lag) on inclination angle suggests that may be associated a geometrical effect, e.g., precession source due to frame-dragging near spining hole. Here, scenario Lense-Thirring source, we use...
We calculate optically thick but geometrically thin (and slim) accretion disk models and perform a ray-tracing of photons (in the Kerr geometry) to observed spectra. Previously, it was common practice ray-trace assuming that they are emitted from geometry equatorial plane, z = 0. show spectra calculated with this assumption differ these under actual surface disc, H(r). This implies knowledge location disks effective photosphere is relevant for calculating In paper we investigate, in terms...
Black hole X-ray binaries are ideal environments to study the accretion phenomena in strong gravitational potentials. These systems undergo dramatic state transitions and analysis of spectra is used probe properties disc its evolution. In this work, we present a systematic investigation $\sim$1800 obtained by RXTE PCA observations GRO J1655-40 LMC X-3 explore nature via non-relativistic relativistic models describing thermal emission black-hole binaries. We demonstrate that modelling...