A5043144883- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Solar and Space Plasma Dynamics
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Radio Astronomy Observations and Technology
- Astronomy and Astrophysical Research
- History and Developments in Astronomy
- Relativity and Gravitational Theory
- Cosmology and Gravitation Theories
- Ionosphere and magnetosphere dynamics
- Mechanics and Biomechanics Studies
- Fluid Dynamics and Turbulent Flows
- High-pressure geophysics and materials
- Astro and Planetary Science
- Particle Accelerators and Free-Electron Lasers
- Geophysics and Gravity Measurements
- Magnetic confinement fusion research
- Laser-Plasma Interactions and Diagnostics
- Astronomical Observations and Instrumentation
- Black Holes and Theoretical Physics
- Particle accelerators and beam dynamics
University of Colorado Boulder
2013-2024
National Institute of Standards and Technology
2015-2024
Joint Institute for Laboratory Astrophysics
2012-2023
University of Colorado System
1989-2020
Planetary Science Institute
2017-2020
Max Planck Institute for Astronomy
2019
Max Planck Society
2019
University of Geneva
2016
University of Amsterdam
2016
Swiss Institute of Comparative Law
2016
Powerful extragalactic radio sources comprise two extended regions containing magnetic field and synchrotron-emitting relativistic electrons, each linked by a jet to central compact source located in the nucleus of associated galaxy. These jets are collimated streams plasma that emerge from opposite directions, along which flow mass, momentum, energy, flux. Methods using observations diagnostically infer pressures, densities, fluid velocities within explained. The terminate components, where...
Gas supplied conservatively to a black hole at rates well below the Eddington rate may not be able radiate effectively and net energy flux, including transported by viscous torque, is likely close zero all radii. This has consequence that gas accretes with positive so it escape. Accordingly, we propose only small fraction of actually falls on hole, binding releases radially outward torque as drive away remainder in form wind. generalization an alternative 'ADAF' solution. Some observational...
Recent Energy Gamma Ray Experiment Telescope (EGRET) observations of blazars have revealed strong, variable gamma-ray fluxes with no signatures absorption by pair production. This radiation probably originates from the inner parts relativistic jets which are aimed nearly toward us. On sub-parsec scales, jet will be pervaded broad-line region, as well photons central continuum source (some scattered thermal plasma). In a frame moving outflow, energy this ambient would enhanced. Comptonized...
We describe a mechanism by which supermassive black holes can form directly in the nuclei of protogalaxies, without need for seed left over from early star formation. Self-gravitating gas dark matter halos lose angular momentum rapidly via runaway, global dynamical instabilities, so-called "bars within bars" mechanism. This leads to rapid buildup dense, self-gravitating core supported pressure - surrounded radiation pressure-dominated envelope gradually contracts and is compressed further...
view Abstract Citations (591) References (40) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Molecular Tori in Seyfert Galaxies: Feeding the Monster and Hiding It Krolik, Julian H. ; Begelman, Mitchell C. Much evidence exists that majority of nuclei are surrounded by a geometrically optically thick torus dusty, obscuring gas few parsecs from center. We discuss principal properties torus. is almost certainly not smoothly distributed; most its mass gathered...
view Abstract Citations (494) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Overpressured Cocoons in Extragalactic Radio Sources Begelman, Mitchell C. ; Cioffi, Denis F. We show that the cocoons of shocked gas which surround powerful double radio sources can have significantly higher pressures than surrounding intergalactic medium. The be high enough to confine jets these sources, obviating need for magnetic confinement. cocoon pressure and...
We present timing analysis for a Rossi X-ray Timing Explorer observation of Cygnus X-1 in its hard/low state. This was the first RXTE Cyg taken after it transited back to this state from soft/high RXTE's large effective area, superior capabilities, and ability obtain long, uninterrupted observations have allowed us measurements power spectral density (PSD), coherence function, Fourier time lags decade lower frequency half higher than typically achieved with previous instruments. Notable...
view Abstract Citations (478) References (33) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Compton heated winds and coronae above accretion disks. I. Dynamics. Begelman, M. C. ; McKee, F. Shields, G. A. X rays emitted in the inner part of an disk system can heat surface farther out, producing a corona possibly driving off strong wind. The dynamics Compton-heated are analyzed using approximate two-dimensional technique to estimate mass loss rate as function...
We study the efficiency and dynamics of supermassive black hole binary mergers driven by angular momentum loss to small-scale gas discs. Such binaries form after major galaxy mergers, but their fate is unclear since hardening through stellar scattering becomes very inefficient at subparsec distances. Gas discs may dominate on these scales, promote mergers. Using numerical simulations, we investigate evolution semimajor axis eccentricity embedded within geometrically thin Our simulations...
The fast TeV variability of the blazars Mrk 501 and PKS 2155--304 implies a compact emitting region that moves with bulk Lorentz factor Gamma_{em}~100 toward observer. is clearly in excess jet factors Gamma_j\simless 10 measured on sub-pc scales these sources. We propose emission originates from regions move relativistically {\it within} Gamma_j~10. This can be physically realized Poynting flux-dominated jet. show if large fraction luminosity prone to magnetic dissipation through...
Abstract High-resolution spectra of Galactic black holes (GBHs) reveal the presence highly ionized absorbers. In one GBH, accreting close to Eddington limit for more than a decade, powerful accretion disc wind is observed be present in softer X-ray states and it has been suggested that can carry away enough mass energy quench radio jet. Here we report these winds, which may have outflow rates order inner rate or higher, are ubiquitous component jet-free soft all GBHs. We furthermore...
It is generally accepted that astrophysical sources cannot emit synchrotron radiation above 160 MeV in their rest frame. This limit given by the balance between accelerating electric force and reaction acting on electrons. The discovery of gamma-ray flares Crab Nebula, well this limit, challenges classical picture particle acceleration. To overcome particles must accelerate a region high field low magnetic field. possible only with non-ideal magnetohydrodynamic process, like reconnection. We...
ABSTRACT Using two-dimensional particle-in-cell simulations, we characterize the energy spectra of particles accelerated by relativistic magnetic reconnection (without guide field) in collisionless electron–positron plasmas, for a wide range upstream magnetizations σ and system sizes L . The particle are well-represented power law , with combination exponential super-exponential high-energy cutoffs, proportional to respectively. For large power-law index α approaches about 1.2.
Magnetic reconnection in relativistic collisionless plasmas can accelerate particles and power high-energy emission various astrophysical systems. Whereas most previous studies focused on pair plasmas, less attention has been paid to electron–ion plasma reconnection, expected black hole accretion flows jets. We report a comprehensive particle-in-cell numerical investigation of an plasma, spanning wide range ambient ion magnetizations σi, from the semirelativistic regime (ultrarelativistic...
Abstract Insights from JWST observations suggest that active galactic nuclei feedback evolved a short-lived, high-redshift phase in which radiatively cooled turbulence and/or momentum-conserving outflows stimulated vigorous early star formation (“positive” feedback), to late, energy-conserving depleted halo gas reservoirs and quenched formation. The transition between these two regimes occurred at z ∼ 6, independently of galaxy mass, for simple assumptions about the process. Observational...
Abstract We present multifrequency (5–345 GHz) and multiresolution radio observations of 1ES 1927+654, widely considered one the most unusual extreme changing-look active galactic nuclei (CL-AGNs). The source was first designated a CL-AGN after an optical outburst in late 2017 has since displayed considerable changes X-ray emission, including destruction rebuilding corona 2019–2020. Radio prior to 2023 show faint compact typical radio-quiet AGN. Starting February, 1927+654 began exhibiting...
Radiation pressure-dominated accretion disks are predicted to exhibit strong density inhomogeneities on scales much smaller than the disk scale height, due nonlinear development of photon bubble instability. would escape from such a "leaky" at rate higher that by standard theory. The height is then similar without small-scale inhomogeneities, and can remain geometrically thin even as flux approaches exceeds Eddington limit. An idealized one-zone model for with radiation-driven suggests...
Two-dimensional (axially symmetric) numerical hydrodynamical calculations of accretion flows that cannot cool through emission radiation are presented. The begin from an equilibrium configuration consisting a thick torus with constant specific angular momentum. Accretion is induced by the addition small anomalous azimuthal shear stress which characterized function ν. We study generated as amplitude and form ν varied. A spherical polar grid spans more than two orders magnitude in radius used...
Astrophysical jets and pulsar-fed supernova remnants (plerions) are expected to develop highly organized magnetic structures dominated by concentric loops of toroidal field, Bϕ. It has been argued that such could explain the polarization properties some contribute their lateral confinement through tension forces. A field geometry is also central Rees-Gunn model for Crab Nebula, archetypal plerion, leads deduction pulsar's wind must have a weak field. Yet this kind equilibrium between gas...
We present XMM-Newton European Photon Imaging Camera (EPIC) observations of the bright Seyfert 1 galaxy MCG–6-30-15, focusing on broad Fe Kα line at ∼6 keV and associated reflection continuum, which is believed to originate from inner accretion disc. find these features be extremely redshifted, indicating an origin in very central regions It seems likely that we have caught this source 'deep minimum' state first observed by Iwasawa et al. The implied concentration X-ray illumination...
We present the first results from a 500 ks Chandra ACIS-I observation of M87. At soft energies (0.5-1.0 keV), we detect filamentary structures associated with eastern and southwestern X-ray radio arms. Many filaments are spatially resolved widths ~300 pc. This structure is particularly striking in arm, where suggest outer edges series plasma-filled, buoyant bubbles whose ages differ by ~6 × 106 yr. These may be influenced magnetic filamentation. hard (3.5-7.5 nearly circular ring radius 2.8'...