Michal Dovčiak
A5012203328- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Mechanics and Biomechanics Studies
- Gamma-ray bursts and supernovae
- High-pressure geophysics and materials
- Galaxies: Formation, Evolution, Phenomena
- Astronomical Observations and Instrumentation
- Particle Accelerators and Free-Electron Lasers
- Scientific Measurement and Uncertainty Evaluation
- Stellar, planetary, and galactic studies
- Solar and Space Plasma Dynamics
- Astronomy and Astrophysical Research
- Radio Astronomy Observations and Technology
- Astrophysics and Star Formation Studies
- Particle Detector Development and Performance
- Adaptive optics and wavefront sensing
- Calibration and Measurement Techniques
- Astro and Planetary Science
- Relativity and Gravitational Theory
- Neutrino Physics Research
- Superconducting Materials and Applications
- Heat Transfer Mechanisms
- Particle accelerators and beam dynamics
- Particle physics theoretical and experimental studies
Czech Academy of Sciences, Astronomical Institute
2015-2024
Czech Academy of Sciences
2004-2023
Roma Tre University
2010-2022
Astronomical Institute of the Slovak Academy of Sciences
2004-2022
Marshall Space Flight Center
2022
Max Planck Institute for Extraterrestrial Physics
2016
Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
2016
European Space Astronomy Centre
2016
Centro de Astrobiología
2016
Charles University
1997-2010
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,...
Launched on 2021 December 9, the Imaging X-ray Polarimetry Explorer (IXPE) is a NASA Small Mission in collaboration with Italian Space Agency (ASI). The mission will open new window of investigation—imaging x-ray polarimetry. observatory features three identical telescopes, each consisting mirror module assembly polarization-sensitive imaging detector at focus. A coilable boom, deployed orbit, provides necessary 4-m focal length. utilizes three-axis-stabilized spacecraft, which services such...
A black hole x-ray binary (XRB) system forms when gas is stripped from a normal star and accretes onto hole, which heats the sufficiently to emit x-rays. We report polarimetric observation of XRB Cygnus X-1 using Imaging Polarimetry Explorer. The electric field position angle aligns with outflowing jet, indicating that jet launched inner emitting region. polarization degree (4.01+-0.20)% at 2 8 kiloelectronvolts, implying accretion disk viewed closer edge-on than orbit. observations reveal...
Abstract Most of the light from blazars, active galactic nuclei with jets magnetized plasma that point nearly along line sight, is produced by high-energy particles, up to around 1 TeV. Although are known be ultimately powered a supermassive black hole, how particles accelerated such high energies has been an unanswered question. The process must related magnetic field, which can probed observations polarization jets. Measurements radio optical polarization—the only range available until...
ABSTRACT We present an X-ray spectropolarimetric analysis of the bright Seyfert galaxy NGC 4151. The source has been observed with Imaging Polarimetry Explorer (IXPE) for 700 ks, complemented simultaneous XMM–Newton (50 ks) and NuSTAR (100 pointings. A polarization degree Π = 4.9 ± 1.1 per cent angle Ψ 86° 7° east north (68 confidence level) are measured in 2–8 keV energy range. shows that could be entirely due to reflection. Given low reflection flux IXPE band, this requires, however, a...
Abstract We report on an observational campaign the bright black hole (BH) X-ray binary Swift J1727.8–1613 centered around five observations by Imaging Polarimetry Explorer. These track for first time evolution of polarization a BH across hard to soft state transition. The 2–8 keV degree decreased from ∼4% ∼3% observations, but angle remained oriented in north–south direction throughout. Based with Australia Telescope Compact Array, we find that intrinsic 7.25 GHz radio aligns polarization....
Abstract Black hole X-ray binaries exhibit different spectral and timing properties in accretion states. The outburst of a recently discovered extraordinarily bright source, Swift J1727.8–1613, has enabled the first investigation how polarization source evolve with state. 2–8 keV degree was previously measured by Imaging Polarimetry Explorer (IXPE) to be ≈4% hard intermediate Here we present new IXPE results taken soft state, flux dominated thermal disk emission. We find that dropped...
Accreting black holes are believed to emit X-rays which then mediate information about strong gravity in the vicinity of emission region. We report on a set new routines for Xspec package analysing X-ray spectra black-hole accretion disks. The computational tool significantly extends capabilities currently available fitting procedures that include effects gravity, and allows one systematically explore constraints more model parameters than previously possible (for example angular momentum)....
We present the first systematic physical modelling of time-lag spectra between soft (0.3–1 keV) and hard (1.5–4 X-ray energy bands, as a function Fourier frequency, in sample 12 active galactic nuclei which have been observed by XMM–Newton. concentrate particularly on negative time-lags (typically seen above 10−4 Hz), i.e. soft-band variations lag hard-band variations, we assume that they are produced reprocessing reflection accretion disc within lamp-post source geometry. also response...
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 Thermal reverberation in accretion discs of active galactic nuclei is thought to be the reason continuum UV/optical time lags seen these sources. Recently, we studied thermal a standard Novikov-Thorne disc illuminated by an X–ray point-like source, and derived analytic prescription for as function wavelength. In this work, use fit time-lags spectra seven Seyferts, that have been intensively monitored, many wave-bands, last few years. We find can explain observed all Contrary...
Abstract Particle acceleration mechanisms in supermassive black hole jets, such as shock acceleration, magnetic reconnection, and turbulence, are expected to have observable signatures the multiwavelength polarization properties of blazars. The recent launch Imaging X-Ray Polarimetry Explorer (IXPE) enables us, for first time, use X-ray band (2–8 keV) probe jet synchrotron emission high-synchrotron-peaked BL Lac objects (HSPs). We report discovery linear (degree Π x = 15% ± 2% electric...
We report on the first detection of linearly polarized x-ray emission from an ultra-magnetized neutron star with Imaging X-ray Polarimetry Explorer (IXPE). The IXPE 35 observations anomalous pulsar 4U 0142+61 reveal a linear polarization degree $(12\pm 1)\%$ throughout 2--8 keV band. detect substantial variation energy: is $(14\pm at 2--4 and $(41\pm 7)\%$ 5.5--8 keV, while it drops below instrumental sensitivity around 4--5 where angle swings by $\sim 90^\circ$. give us completely new...
Abstract We report the first detection of X-ray polarization bright transient Swift J1727.8−1613 with Imaging Polarimetry Explorer. The observation was performed at beginning 2023 discovery outburst, when source resided in hard state. find a time- and energy-averaged degree 4.1% ± 0.2% angle 2.°2 1.°3 (errors 68% confidence level; this translates to ∼20 σ significance detection). This finding suggests that hot corona emitting bulk detected X-rays is elongated, rather than spherical....
Abstract We present the IXPE observation of GRB 221009A, which includes upper limits on linear polarization degree both prompt and afterglow emission in soft X-ray energy band. 221009A is an exceptionally bright gamma-ray burst (GRB) that reached Earth 2022 October 9 after traveling through dust Milky Way. The Imaging Polarimetry Explorer (IXPE) pointed at 11 to observe, for first time, 2–8 keV a afterglow. set limit 13.8% 99% confidence level. This result provides constraints jet opening...
Abstract The lower-energy peak of the spectral energy distribution blazars has commonly been ascribed to synchrotron radiation from relativistic particles in jets. Despite consensus regarding jet emission processes, particle acceleration mechanism is still debated. Here, we present first X-ray polarization observations PG 1553+113, a high-synchrotron-peak blazar observed by Imaging Polarimetry Explorer (IXPE). We detect an degree (10 ± 2)% along electric-vector position angle ψ X = 86° 8°....
ABSTRACT We present an X-ray spectro-polarimetric analysis of the bright Seyfert galaxy IC 4329A. The Imaging Polarimetry Explorer (IXPE) observed source for ∼500 ks, supported by XMM–Newton (∼60 ks) and NuSTAR (∼80 exposures. detect polarization in 2–8 keV band with 2.97σ confidence. report a degree 3.3 ± 1.1 per cent angle 78° 10° (errors are 1σ confidence). is consistent being aligned radio jet, albeit partially due to large uncertainties on position angle. jointly fit spectra from three...
After about 16 years since its first outburst, the transient neutron star low-mass X-ray binary XTE J1701$-$462 turned on again in September 2022, allowing for study of polarimetric characteristics by a dedicated observing program with Imaging Polarimeter Explorer (IXPE). Polarimetric studies have been expected to improve our understanding accreting weakly magnetized stars, particular, physics and geometry hot inner regions close compact object. The IXPE data two triggered observations were...