Alexandra Veledina
A5089180875- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Mechanics and Biomechanics Studies
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- High-pressure geophysics and materials
- Astronomical Observations and Instrumentation
- Astronomy and Astrophysical Research
- Relativity and Gravitational Theory
- Scientific Measurement and Uncertainty Evaluation
- Solar and Space Plasma Dynamics
- Galaxies: Formation, Evolution, Phenomena
- Advanced X-ray Imaging Techniques
- Adaptive optics and wavefront sensing
- Astrophysics and Star Formation Studies
- Particle Accelerators and Free-Electron Lasers
- Geophysics and Sensor Technology
- Black Holes and Theoretical Physics
- Radio Astronomy Observations and Technology
- Ionosphere and magnetosphere dynamics
- Astro and Planetary Science
- Multidisciplinary Science and Engineering Research
- Geophysics and Gravity Measurements
- Heat Transfer Mechanisms
- Stellar, planetary, and galactic studies
University of Turku
2015-2024
KTH Royal Institute of Technology
2015-2024
Stockholm University
2015-2024
Space Research Institute
2018-2022
Nordic Institute for Theoretical Physics
2021-2022
Russian Academy of Sciences
2021-2022
Vaisala (Finland)
2014-2018
University of Oulu
2011-2015
Hebrew University of Jerusalem
2011
Czech Academy of Sciences, Institute of Physics
2011
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 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 Recent X-ray polarimetric data on the prototypical black hole binary Cyg X-1 from Imaging Polarimetry Explorer present tight constraints accretion geometry in hard spectral state. Contrary to general expectations of a low, ≲1% polarization degree (PD), observed average PD was found be factor 4 higher. Aligned with jet position angle sky, favors emission region stretched normally disk plane. The high is, however, difficult reconcile low orbital inclination i ≈ 30°. We suggest that...
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...
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 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...
ABSTRACT We report on an X-ray polarimetric observation of the high-mass binary LMC X-1 in high/soft state, obtained by Imaging Polarimetry Explorer (IXPE) 2022 October. The measured polarization is below minimum detectable 1.1 per cent (at 99 confidence level). Simultaneously, source was observed with Neutron Star Interior Composition (NICER), Nuclear Spectroscopic Telescope Array (NuSTAR), and Spectrum-Rontgen-Gamma (SRG)/Astronomical Roentgen – Concentrator (ART-XC) instruments, which...
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...
Abstract The Imaging X-ray Polarimetry Explorer measured with high significance the polarization of brightest Z-source, Sco X-1, resulting in nominal 2–8 keV energy band a degree 1.0% ± 0.2% and angle 8° 6° at 90% confidence level. This observation was strictly simultaneous observations performed by NICER, NuSTAR, Insight-HXMT, which allowed for precise characterization its broadband spectrum from soft to hard X-rays. source has been observed mainly state, short periods flaring. We also...
We present the results of first X-ray polarimetric observation low-mass binary 4U 1957+115, performed with Imaging Polarimetry Explorer in May 2023. The system has been a high-soft spectral state since its discovery and is thought to host black hole. ∼571 ks reveals linear polarisation degree 1.9%±0.6% angle −41.°8±7.°9 2–8 keV energy range. Spectral modelling consistent dominant contribution coming from standard accretion disc, while data suggest significant role returning radiation:...
Abstract Cir X-1 is a neutron star X-ray binary characterized by strong variations in flux during its eccentric ∼16.6 day orbit. There are also the spectral state, and it has historically shown both atoll Z state properties. We observed source with Imaging Polarimetry Explorer two orbital segments, 6 days apart, for total of 263 ks. find an polarization degree these segments 1.6% ± 0.3% 1.4% at angles 37° 5° −12° 7°, respectively. Thus, we rotation angle 49° 8° along Because accretion flow,...
X-ray polarimetry is a fine tool for probing the accretion geometry and physical processes operating in proximity of compact objects, such as black holes neutron stars. Recent discoveries made by Imaging Polarimetry Explorer question our understanding picture. The observed high levels polarization binaries active galactic nuclei are challenging to achieve within conventional scenarios. We investigate possibility that fraction (or even all) polarized signal arises from scattering equatorial...
Multiwavelength observations of Galactic black hole transients have opened a new path to understanding the physics innermost parts accretion flows. While processes giving rise their X-ray continuum been studied extensively, emission in optical and infrared (OIR) energy bands was less investigated remains poorly understood. The standard disc, which may contribute flux at these wavelengths, is not capable explaining number observables: excesses, fast OIR variability complicated correlation...
We report on the first observation of a radio-quiet Active Galactic Nucleus (AGN) using polarized X-rays: Seyfert 1.9 galaxy MCG-05-23-16. This source was pointed with Imaging X-ray Polarimetry Explorer (IXPE) starting May 14, 2022 for net observing time 486 ks, simultaneously XMM-Newton (58 ks) and NuSTAR (83 ks). A polarization degree smaller than $\Pi<4.7\%$ (at 99% c.l.) is derived in 2-8 keV energy range, where emission dominated by primary component ascribed to hot corona. The...
The observational signatures of black holes in x-ray binary systems depend on their masses, spins, accretion rate, and the misalignment angle between hole spin orbital angular momentum. We present optical polarimetric observations MAXI J1820+070, from which we constrain position orbital. Combining this with previous determinations relativistic jet orientation, traces spin, inclination orbit, determine a lower limit 40° spin-orbit angle. must originate either evolution or formation stages. If...
ABSTRACT We report on the second observation of radio-quiet active galactic nucleus MCG-05-23-16 performed with Imaging X-ray Polarimetry Explorer (IXPE). The started 2022 November 6 for a net observing time 640 ks, and was partly simultaneous NuSTAR (86 ks). After combining these data those obtained in first IXPE pointing May (simultaneous XMM–Newton NuSTAR) we find 2–8 keV polarization degree Π = 1.6 ± 0.7 (at 68 per cent confidence level), which corresponds to an upper limit 3.2 99...
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...
Abstract We present the first X-ray polarimetric study of dipping accreting neutron star 4U 1624−49 with Imaging Polarimetry Explorer. report a detection polarization in nondip time intervals confidence level 99.99%. find an average degree (PD) 3.1% ± 0.7% and angle 81° 6° east north 2–8 keV band. upper limit on PD 22% during dips 95% confidence. The increases energy, reaching from 3.0% 0.9% 4–6 band to 6% 2% 6–8 This indicates likely arises Comptonization. high observed is unlikely be...
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...
Weakly magnetized neutron stars in X-ray binaries show a complex phenomenology with several spectral components that can be associated the accretion disk, boundary, and/or spreading layer, corona, and wind. Spectroscopic information alone, however, is not enough to distinguish these components. The analysis of timing data revealed most variability, particular, kilohertz quasi-period oscillations, are high-energy component corresponds boundary layer. Additional about nature components,...
We report on the detection of X-ray polarisation in black-hole binary Swift J1727.8$-$1613 during its dim hard spectral state by Imaging Polarimetry Explorer (IXPE). This is first at transition from soft to an binary. find averaged 2$-$8 keV degree (3.3 ${\pm}$ 0.4) % and a corresponding angle 3{\deg} 4{\deg}, which matches detected rising stage outburst, September$-$October 2023, within 1${\sigma}$ uncertainty. The observational campaign complements previous studies this source enables...
How black holes consume and eject matter has been the subject of intense studies for more than 60 years. The luminosity these systems are often compared to Eddington limit, border at which spherical accretion is inhibited by radiation pressure photons it produces. discovery ultraluminous X-ray sources (ULXs) showed that can proceed even when apparent exceeds limit (Kaaret et al. 2017). High might be produced beaming incident a thick collimated outflow or truly super-Eddington flow. However,...