A5106525913- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- High-pressure geophysics and materials
- Gamma-ray bursts and supernovae
- Mechanics and Biomechanics Studies
- Astrophysics and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Particle Detector Development and Performance
- Scientific Measurement and Uncertainty Evaluation
- X-ray Spectroscopy and Fluorescence Analysis
- Adaptive optics and wavefront sensing
- Astro and Planetary Science
- Geophysics and Gravity Measurements
- Solar and Space Plasma Dynamics
- Galaxies: Formation, Evolution, Phenomena
- Geophysics and Sensor Technology
- Particle Accelerators and Free-Electron Lasers
- Ionosphere and magnetosphere dynamics
- Superconducting Materials and Applications
- Atomic and Molecular Physics
- Calibration and Measurement Techniques
- Superconducting and THz Device Technology
University of Groningen
2015-2024
Astronomical Institute of the Slovak Academy of Sciences
1997-2024
University of Kassel
2023
Miami Dade College
2021
Astronomy and Space
2009-2019
National Institute for Astrophysics
2010-2016
University of Geneva
2016
SRON Netherlands Institute for Space Research
2001-2014
Consejo Superior de Investigaciones Científicas
2012
Brera Astronomical Observatory
2010
We present the results of timing and color analysis more than two hundred RXTE/PCA observations bright black-hole transient GX 339–4 obtained during its 2002/2003 outburst. The color-intensity evolution system, coupled to properties fast time variability, allow identification four separate states. Depending on state, strong noise is detected, together with a variety quasi-periodic oscillations at frequencies from 0.2 8 Hz. characterization parameters these states compare them what has been...
The X-ray Integral Field Unit (X-IFU) is the high resolution spectrometer of ESA Athena observatory. Over a field view 5' equivalent diameter, it will deliver spectra from 0.2 to 12 keV with spectral 2.5 eV up 7 on ∼ 5" pixels. X-IFU based large format array super-conducting molybdenum-gold Transition Edge Sensors cooled at 90 mK, each coupled an absorber made gold and bismuth pitch 249 μm. A cryogenic anti-coincidence detector located underneath prime TES enables non background be reduced....
We present an analysis of RXTE data the X-ray transient XTE J1550-564. The source went through several states, which were divided into spectrally soft and hard states. These states showed up as distinct branches in color-color diagram, forming a structure with comb-like topology; state branch spine teeth. Variability was strongly correlated position on branches. broad band noise became stronger, changed from power law like to limited, spectrum harder. Three types QPOs found: 1-18 Hz 102-284...
The X-ray Integral Field Unit (X-IFU) on board the Advanced Telescope for High-ENergy Astrophysics (Athena) will provide spatially resolved high-resolution spectroscopy from 0.2 to 12 keV, with 5 arc second pixels over a field of view minute equivalent diameter and spectral resolution 2.5 eV up 7 keV. In this paper, we first review core scientific objectives Athena, driving main performance parameters X-IFU, namely resolution, view, effective area, count rate capabilities, instrumental...
ABSTRACT Low-mass X-ray binaries (LMXBs) show strong variability over a broad range of time-scales. The analysis this variability, in particular the quasi-periodic oscillations (QPO), is key to understanding properties innermost regions accretion flow these systems. We present time-dependent Comptonization model that fits energy-dependent rms-amplitude and phase-lag spectra low-frequency QPOs black hole (BH) LMXBs. disc as multitemperature blackbody source emitting soft photons are then...
We have analyzed the X-ray spectra of microquasar GRS 1915+105, as observed with Proportional Counter Array (PCA) on Rossi X-Ray Timing Explorer, during periods stable weak emission, outbursts, and rapid flaring. find that complicated intensity curve this source can be described by removal replenishment matter forming inner part an optically thick accretion disk, probably caused a thermal-viscous instability analogous to operating in dwarf novae, but here driven Lightman-Eardley instability....
We have analyzed the spectral variations of superluminal black-hole X-ray binary GRS 1915+105 by using data obtained with PCA on Rossi XTE. find that, despite marked differences in structure and time scale variability, all changes can be attributed to rapid disappearing inner region an accretion disk, followed a slower re-filling emptied region. The for each event is determined extent missing part disk. observed relation between duration radius matches remarkably well expected dependence...
We report the discovery of nonthermal pulsed X-ray/soft gamma-ray emission up to ~150 keV from anomalous 11.8 s X-ray pulsar AXP 1E 1841-045 located near center supernova remnant Kes 73 using Rossi X-Ray Timing Explorer (RXTE) Proportional Counter Array and High Energy Experiment (HEXTE) data. The morphology double-peaked pulse profile changes rapidly with energy 2 ~8 keV, above which shape remains more or less stable. spectrum is very hard; its 10 can be described well by a power law photon...
We report on an analysis of Rossi X-Ray Timing Explorer data the transient neutron star low-mass X-ray binary (NS-LMXB) XTE J1701–462, obtained during its 2006–2007 outburst. The properties source changed between those various types NS-LMXB subclasses. At high luminosities, switched two Z behavior and at low luminosities we observed a transition from to atoll behavior. These transitions subclasses primarily manifest themselves as changes in shapes tracks color–color (CD) hardness-intensity...
Context.The hot X-ray emitting gas in clusters of galaxies is a very large repository metals produced by supernovae. During the evolution clusters, billions supernovae eject their material into this Intra-Cluster Medium (ICM).
We studied the low-frequency quasi-periodic oscillations (LFQPOs) in black hole GRO J1655−40 during 2005 outburst, using data from Rossi X-ray Timing Explorer. All LFQPOs could be identified as either type B or C previously proposed classification schemes. In soft state of outburst type-C reached frequencies that are among highest ever seen for holes. At peak ultraluminous state, power spectrum showed two simultaneous, non-harmonically related peaks which we a type-B and QPO. The...
We present the results of analysis a large data base X-ray observations 22 galactic black hole transients with Rossi X-Ray Timing Explorer throughout its operative life for total exposure time ∼12 ms. excluded persistent systems and peculiar source GRS 1915+105, as well most recently discovered sources. The semi-automatic homogeneous was aimed at detection high-frequency (100–1000 Hz) quasi-periodic oscillations (QPO), which several cases were previously reported in literature. After taking...
Inverse Compton scattering dominates the high energy part of spectra neutron star (NS) low mass X-ray binaries (LMXBs). It has been proposed that inverse also drives radiative properties kilohertz quasi periodic oscillations (kHz QPOs). In this work, we construct a model predicts dependence rms amplitude and time lag kHz QPOs. Using model, fit lower QPO in NS LMXB 4U 1636-53 over 11 frequency intervals report three important findings: (i) A medium extends 1-8 km above surface is required to...
ABSTRACT Spectral-timing analysis of the fast variability observed in X-rays is a powerful tool to study physical and geometrical properties accretion/ejection flows black hole (BH) binaries. The origin type-B quasi-periodic oscillations (QPO), predominantly BH candidates soft-intermediate state, has been linked emission arising from relativistic jet. In this X-ray spectrum characterized by soft-thermal blackbody-like due accretion disc, an iron line (in 6–7 keV range), power-law-like hard...
Most models of the low frequency quasi periodic oscillations (QPOs) in low-mass X-ray binaries (LMXBs) explain dynamical properties those QPOs. On other hand, recent years reverberation that assume a lamp-post geometry have been successfull explaining energy-dependent time lags broad-band noise component stellar mass black-holes and active galactic nuclei. We recently shown Comptonisation can spectral-timing kilo-hertz (kHz) QPOs observed neutron star (NS) LMXBs. It is therefore worth...
Type-C quasi-periodic oscillations (QPOs) in black hole X-ray transients can appear when the source is low-hard and hard-intermediate states. The spectral-timing evolution of type-C QPO MAXI J1535-571 has been recently studied with Insight-HXMT. Here we fit simultaneously time-averaged energy spectrum, using a relativistic reflection model, fractional rms phase-lag spectra QPOs, developed time-dependent Comptonization model was intermediate state. We show, for first time, that successfully...
ABSTRACT The inverse Compton process by which soft photons are up-scattered hot electrons in a corona plays fundamental role shaping the X-ray spectra of black hole (BH) low-mass binaries (LMXBs), particularly hard and hard-intermediate states. In these states, power-density sources typically show Type-C low-frequency quasi-periodic oscillations (QPOs). Although several models have been proposed to explain dynamical origin their frequency, only few those predict spectral-timing radiative...
We present a detailed spectral and temporal analysis of the black-hole candidate MAXI~J1535$-$571 using NICER observations in September October 2017. focus specifically on hard-intermediate state when source shows type-C quasi-periodic oscillations (QPOs). fitted time-averaged spectrum rms phase-lag spectra QPO with one-component time-dependent Comptonization model. found that corona contracts from $\sim 10^4$ to 3 \times 10^3$ km as frequency increases 1.8$ Hz 9.0$ Hz. The fits suggest...
A recent study shows that if the power spectra (PS) of accreting compact objects consist a combination Lorentzian functions are coherent in different energy bands but incoherent with each other, same is true for real and imaginary parts cross spectrum (CS). Using this idea, we discovered quasi-periodic oscillations (QPOs) NICER observations black hole candidate MAXI J1820+070. The QPOs appear as narrow features small large part CS not significantly detected PS when they overlap frequency...