A5023792827- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Radio Astronomy Observations and Technology
- Galaxies: Formation, Evolution, Phenomena
- Mechanics and Biomechanics Studies
- Dark Matter and Cosmic Phenomena
- Particle Detector Development and Performance
- Astronomical Observations and Instrumentation
- Astronomy and Astrophysical Research
- High-pressure geophysics and materials
- Particle Accelerators and Free-Electron Lasers
- Solar and Space Plasma Dynamics
- Relativity and Gravitational Theory
- Stellar, planetary, and galactic studies
- Geophysics and Gravity Measurements
- Neutrino Physics Research
- Cosmology and Gravitation Theories
- Black Holes and Theoretical Physics
- Superconducting Materials and Applications
- Astrophysics and Star Formation Studies
- Magnetic confinement fusion research
- Experimental and Theoretical Physics Studies
- Particle physics theoretical and experimental studies
University of Amsterdam
2016-2025
Netherlands Institute for Radio Astronomy
2017-2024
Applied Mathematics (United States)
2024
University of Arizona
1997-2024
TU Dortmund University
2023
University of Łódź
2023
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
2023
University of Turku
2023
Niels Brock
2023
University of Copenhagen
2023
We explore the evolution in power of black holes all masses, and their associated jets, within scheme an accretion rate-dependent state transition. Below a critical value rate systems are assumed to undergo transition where dominant mode is optically thin radiatively inefficient. In these significantly sub-Eddington systems, spectral energy distribution predicted be dominated by non-thermal emission from relativistic jet whereas near-Eddington will instead disk. Reasonable candidates for...
The hard state of X-ray binaries (XRBs) is characterized by a power law spectrum in the band, and flat/inverted radio/IR associated with occasionally imaged compact jets. It has generally been thought that X-rays result from Compton upscattering thermal accretion disk photons hot, coronal plasma whose properties are inferred via spectral fitting. Interestingly, these properties-especially those certain magnetized corona models-are very similar to derived conditions at jet footpoints. Here we...
We present the results of a long-term study black hole candidate GX 339-4 using simultaneous radio (from Australia Telescope Compact Array) and X-ray Rossi Timing Explorer BeppoSAX) observations performed between 1997 2000. find strong evidence for correlation these two emission regimes that extends over more than three decades in flux, down to quiescence level 339-4. This is strongest date such coupling emission. discuss light jet model can explain radio/X-ray correlation. could indicate...
Gas falling into a black hole (BH) from large distances is unaware of BH spin direction, and misalignment between the accretion disc expected to be common. However, physics tilted discs (e.g., angular momentum transport jet formation) poorly understood. Using our new GPU-accelerated code H-AMR, we performed 3D general relativistic magnetohydrodynamic simulations thick around rapidly spinning BHs, at highest resolution date. We explored limit where thermal pressure dominates magnetic...
Most supermassive black holes (SMBHs) are accreting at very low levels and difficult to distinguish from the galaxy centers where they reside. Our own Galaxy's SMBH provides a uniquely instructive exception, we present close-up view of its quiescent X-ray emission based on 3 mega-second Chandra observations. Although is elongated aligns well with surrounding disk massive stars, can rule out concentration low-mass coronally active stars as origin lack predicted Fe Kalpha emission. The...
A heavy black hole in an x-ray binary If a interacts with companion star, the system emits x-rays and can form radio jet. The masses of holes these binaries are all lower than those detected using gravitational waves, challenging models formation from massive stars. Miller-Jones et al. used astrometry to refine distance Cygnus X-1, well-studied binary. They found larger previous estimates, raising mass 21 solar masses. results challenge wind loss rates implemented stellar evolution models....
Abstract Magnetic reconnection can power bright, rapid flares originating from the inner magnetosphere of accreting black holes. We conduct extremely high-resolution (5376 × 2304 cells) general-relativistic magnetohydrodynamics simulations, capturing plasmoid-mediated in a 3D magnetically arrested disk for first time. show that an equatorial, plasmoid-unstable current sheet forms transient, nonaxisymmetric, low-density within few Schwarzschild radii. flux bundles escape event horizon through...
The Event Horizon Telescope (EHT) has led to the first images of a supermassive black hole, revealing central compact objects in elliptical galaxy M87 and Milky Way. Proposed upgrades this array through next-generation EHT (ngEHT) program would sharply improve angular resolution, dynamic range, temporal coverage existing observations. These improvements will uniquely enable wealth transformative new discoveries related hole science, extending from event-horizon-scale studies strong gravity...
Abstract The Event Horizon Telescope Collaboration (EHTC) observed the Galactic centre source Sagittarius A* (Sgr A*) and used emission models primarily based on single ion temperature (1T) general relativistic magnetohydrodynamic (GRMHD) simulations. This predicted is strongly dependent a modelled prescription of ion-to-electron ratio. most promising are magnetically arrested disk (MAD) states. However, nearly all MAD exhibit larger temporal fluctuations in radiative 230 GHz compared to...
The recent Chandra observation of the radio source at center our Galaxy, Sgr A*, puts new constraints on its theoretical models. spectrum is very soft, and rapidly variable. We consider different models to explain observations. find that features X-ray can be marginally explained with an advection-dominated accretion flow (ADAF) model while it does not well fit spectrum. An ADAF strong winds (ADIOS) favored if we assume wind radiate. Alternatively, propose a coupled jet plus disk...
The X-ray mission Chandra has observed a dramatic flare -- brightening by factor of 50 for only three hours from Sgr A*, the Galactic Center supermassive black hole. A* never shown variability this amplitude in radio and we therefore argue that jump order accretion rate does not seem likely cause. Based on our model jet-dominated emission quiescent state suggest is consequence extra electron heating near This can either lead to direct thermal electrons T_e~6*10^11 K significantly increased...
The fundamental plane of black hole activity is a relation between X-ray luminosity, radio and mass for hard state Galactic holes their supermassive analogs. suggests that, at low-accretion rates, the physical processes regulating conversion an accretion flow into radiative energy could be universal across entire scale. However, there still need to further refine in order better discern geometry very close hole, particular source X-rays. Further refinement necessary because error bars on...
Recent X-ray observations reveal an increasing number of sources in nearby galaxies exceeding luminosities . Assuming isotropic emission, the Eddington limit suggests a population intermediate-mass black holes However, Markoff et al. ([CITE]) proposed that jets may be contributing to emission from binaries (XRBs), implying some relativistically beamed. This could reduce required hole masses standard values. To test this hypothesis, we investigate simple synthesis model for point with...
The Galactic black hole candidate X-ray binary GX 339-4 spends most of its time in the low/hard state, making it an ideal for modeling assumedly low accretion phase. radio emission correlates very tightly with X-rays over more than two orders magnitude flux density, suggesting that jet plasma also plays a role at higher frequencies. We compare predictions our model, and without acceleration, to thirteen broadband simultaneous or quasi-simultaneous spectra this changing history. In addition,...
Low frequency radio waves, while challenging to observe, are a rich source of information about pulsars. The LOw Frequency ARray (LOFAR) is new interferometer operating in the lowest 4 octaves ionospheric "radio window": 10-240MHz, that will greatly facilitate observing pulsars at low frequencies. Through huge collecting area, long baselines, and flexible digital hardware, it expected LOFAR revolutionize astronomy frequencies visible from Earth. next-generation telescope pathfinder Square...
We present the first systematic analysis of X-ray variability Sgr A* during Chandra Observatory's 2012 Visionary Project. With 38 High Energy Transmission Grating Spectrometer observations spaced an average 7 days apart, this unprecedented campaign enables detailed study emission from supermassive black hole at high spatial, spectral and timing resolution. In 3 Ms observations, we detect 39 flares A*, lasting a few hundred seconds to approximately 8 ks, ranging in 2–10 keV luminosity ∼1034...
The center of our Galaxy hosts the best constrained supermassive black hole in universe, Sagittarius A* (Sgr A*). Its mass and distance have been accurately determined from stellar orbits proper motion studies, respectively, its high-frequency radio, highly variable near-infrared x-ray emission originate within a few Schwarzschild radii event horizon. theory general relativity (GR) predicts appearance shadow, which is lensed image This shadow can be resolved by very long baseline radio...
Black hole accretion and jet production are areas of intensive study in astrophysics. Recent work has found a relation between radio luminosity, X-ray black mass. With the assumption that luminosities suitable proxies for power power, respectively, broad fundamental connection is implied. In an effort to refine these links enhance their we have explored above relations exclusively among holes with direct, dynamical mass-measurements. This approach not only eliminates systematic errors...
Faraday rotation measurements using the current and next generation of low-frequency radio telescopes will provide a powerful probe astronomical magnetic fields. However, achieving full potential these requires accurate removal time-variable ionospheric contribution. We present ionFR, code that calculates amount for specific epoch, geographic location, line-of-sight. ionFR uses number publicly available, GPS-derived total electron content maps most recent release International Geomagnetic...
We report on deep, coordinated radio and X-ray observations of the black hole binary XTE J1118+480 in quiescence. The source was observed with Karl G. Jansky Very Large Array for a total 17.5 h at 5.3 GHz, yielding 4.8 ± 1.4 μJy position consistent system. At distance 1.7 kpc, this corresponds to an integrated luminosity between 4 8 × 1025 erg s−1, depending spectral index. This is lowest measured any accreting date. Simultaneous Chandra Telescope detected 1.2 10−14 s−1 cm−2 (1–10 keV),...
We present an intensive radio and X-ray monitoring campaign on the 2009 outburst of Galactic black hole candidate binary H1743-322. With high angular resolution Very Long Baseline Array, we resolve jet ejection event measure proper motions ejecta relative to position compact core jets detected at beginning outburst. This allows us accurately couple moment when occurred with spectral timing signatures. find that signatures are best diagnostic in this outburst, which as variability began...