A5080658446- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Galaxies: Formation, Evolution, Phenomena
- High-pressure geophysics and materials
- Mechanics and Biomechanics Studies
- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Relativity and Gravitational Theory
- Cosmology and Gravitation Theories
- Radio Astronomy Observations and Technology
- Solar and Space Plasma Dynamics
- Astro and Planetary Science
- Laser-Plasma Interactions and Diagnostics
- Black Holes and Theoretical Physics
- Geophysics and Gravity Measurements
- Ionosphere and magnetosphere dynamics
- Adaptive optics and wavefront sensing
- Astronomical Observations and Instrumentation
- Heat Transfer Mechanisms
- History and Developments in Astronomy
- Phase Equilibria and Thermodynamics
- Particle Accelerators and Free-Electron Lasers
Dow Chemical (India)
2025
Harvard University
2013-2024
Harvard University Press
1997-2024
Woodwell Climate Research Center
2019-2024
Center for Astrophysics Harvard & Smithsonian
2015-2024
University of Massachusetts Amherst
2021-2023
Dow Chemical (United States)
2011-2021
Freeport-McMoRan (United States)
2021
University of Castilla-La Mancha
2019
Massachusetts Institute of Technology
2015
view Abstract Citations (1959) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Advection-dominated Accretion: A Self-similar Solution Narayan, Ramesh ; Yi, Insu We consider viscous rotating accretion flows in which most of the viscously dissipated energy is stored as entropy rather than being radiated. Such advection-dominated may occur when optical depth either very small or large. obtain a family self-similar solutions where temperature...
The recently discovered gamma-ray burst afterglow is believed to be described reasonably well by synchrotron emission from a decelerating relativistic shell that collides with an external medium. To compare theoretical models observations, we calculate here the broadband spectrum and corresponding light curve of radiation power-law distribution electrons in expanding shock. Both consist several segments related indices. constructed under two limiting for hydrodynamic evolution shock: fully...
Black hole accretion flows can be divided into two broad classes: cold and hot. Cold flows, which consist of cool optically thick gas, are found at relatively high mass rates. Prominent examples the standard thin disk, occurs a fraction Eddington rate, slim disk super-Eddington These responsible for luminous systems such as active galactic nuclei radiating or close to luminosity black X-ray binaries in soft state. Hot topic this review, virially hot thin. They occur lower rates, described by...
Black hole X-ray binaries (BHXBs) are known to display five distinct spectral states. In order of increasing luminosity these the quiescent state, low intermediate high and very state. We present a self-consistent model accretion flows around black holes that unifies all states except The is an extension following paradigm, which has been applied successfully flow consists two zones, inner advection-dominated (ADAF) extends from horizon transition radius rtr, outer thin disk beyond rtr....
view Abstract Citations (1387) References (63) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Advection-dominated Accretion: Underfed Black Holes and Neutron Stars Narayan, Ramesh ; Yi, Insu We describe new optically thin solutions for rotating accretion flows around black holes neutron stars. These are advection dominated, so that most of the viscously dissipated energy is advected radially with flow. model accreting gas as a two-temperature plasma include...
ABSTRACT We describe global, 3D, time-dependent, non-radiative, general-relativistic, magnetohydrodynamic simulations of accreting black holes (BHs). The are designed to transport a large amount magnetic flux the centre, more than gas can force into BH. excess remains outside BH, impedes accretion, and leads magnetically arrested disc. find powerful outflows. For BH with spin parameter = 0.5, efficiency which accretion system generates outflowing energy in jets winds is η≈ 30 per cent. 0.99,...
Search Bar to Enter New Query quick field: Author First Abstract Year Fulltext Select a field or operator abstract only acknowledgements affiliation arXiv category author count bibcode bibliographic group bib abbrev, e.g. ApJ body of article data archive collection citation doctype doi entdate first fulltext identifier inst keyword object orcid page property publication full name date published title volume year citations() pos() references() reviews() similar() topn() trending() useful()...
We consider an accretion flow model originally proposed by Bisnovatyi-Kogan & Ruzmaikin (1974), which has been confirmed in recent 3D MHD simulations. In the model, accreting gas drags a strong poloidal magnetic field to center such that accumulated disrupts axisymmetric at relatively large radius. Inside disruption radius, accretes as discrete blobs or streams with velocity much less than free-fall velocity. Almost entire rest mass energy of is released heat, radiation and...
view Abstract Citations (761) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Advection-dominated Accretion: Self-Similarity and Bipolar Outflows Narayan, Ramesh ; Yi, Insu We consider axisymmetric viscous accretion flows where a fraction f of the viscously dissipated energy is advected with accreting gas as stored entropy 1-f radiated. When small (i.e. very little advection), our solutions resemble standard thin disks in many respects except...
We investigate radiatively inefficient accretion flow models for Sgr A*, the supermassive black hole in our Galactic center, light of new observational constraints. Confirmation linear polarization submillimeter emission argues rates much less than canonical Bondi rate. consider with low and calculate spectra produced by a hybrid electron population consisting both thermal nonthermal particles. The electrons produce can account its properties. As noted previous work, observed low-frequency...
Radio loud active galactic nuclei (AGNs) are on average 1000 times brighter in the radio band compared to quiet AGNs. We investigate whether this loud/quiet dichotomy can be due differences spin of central black holes (BHs) that power radio-emitting jets. Using general relativistic magnetohydrodynamic simulations, we construct steady state axisymmetric numerical models for a wide range BH spins (dimensionless parameter 0.1 ⩽ 0.9999) and variety jet geometries. assume total magnetic flux...
We explore the connection between different classes of active galactic nuclei (AGNs) and evolution their host galaxies, by deriving galaxy properties, clustering, Eddington ratios AGNs selected in radio, X-ray, infrared. study a sample 585 at 0.25 < z 0.8 using redshifts from AGN Galaxy Evolution Survey (AGES) data radio (WSRT 1.4 GHz), X-rays (Chandra XBootes), mid-IR (IRAC Shallow Survey). The IR samples show modest overlap, indicating that to flux limits survey, they represent largely...
We present three-dimensional MHD simulations of rotating radiatively inefficient accretion flows onto black holes. In the simulations, we continuously inject magnetized matter into computational domain near outer boundary, and run calculations long enough for resulting flow to reach a quasi-steady state. have studied two limiting cases geometry injected magnetic field: pure toroidal field poloidal field. case injection, accreting forms nearly axisymmetric, geometrically-thick, turbulent...
We present results from two long-duration GRMHD simulations of advection-dominated accretion around a non-spinning black hole. The first simulation was designed to avoid significant accumulation magnetic flux the This run for time 200,000GM/c^3 and achieved inflow equilibrium out radius \sim90GM/c^2. Even at this relatively large radius, mass outflow rate \dot{M}_{out} is found be only 60% net \dot{M}_{BH} into second achieve substantial hole in magnetically arrested disc. shorter...
Based on a spectral analysis of the X-ray continuum that employs fully relativistic accretion disk model, we conclude compact primary binary source GRS 1915+105 is rapidly rotating Kerr black hole. We find lower limit dimensionless spin parameter a* > 0.98. Our result robust in sense it independent details data and insensitive to uncertainties mass distance Furthermore, our model includes an advanced treatment hardening. selection relies rigorous quantitative definition thermal state hole...
We use dynamical mass measurements of 16 black holes in transient low-mass X-ray binaries to infer the stellar hole distribution parent population. find that observations are best described by a narrow at 7.8 ± 1.2 M☉. identify selection effect related choice targets for optical follow-ups results flux-limited sample. demonstrate, however, this does not introduce bias observed and cannot explain absence 2–5 M☉ range. On high-mass end, we argue rapid decline inferred may be result particular...
We estimate the thermal conductivity of a weakly collisional magnetized plasma with chaotic magnetic field fluctuations. When fluctuation spectrum extends over two or more decades in wavevector, we find that conduction is very efficient; coefficient only factor ~5 below classical Spitzer estimate. suggest could play significant role cooling flows clusters galaxies.
My life has been an interesting voyage. I became astronomer because could not imagine living on Earth and trying to understand how the Universe works. scientific career revolved around observing motions of stars within galaxies ...Read More
Search Bar to Enter New Query quick field: Author First Abstract Year Fulltext Select a field or operator abstract only acknowledgements affiliation arXiv category author count bibcode bibliographic group bib abbrev, e.g. ApJ body of article data archive collection citation doctype doi entdate first fulltext identifier inst keyword object orcid page property publication full name date published title volume year citations() pos() references() reviews() similar() topn() trending() useful()...
We use a ray-tracing technique to compute the observed spectrum of thin accretion disk around Kerr black hole. include all relativistic effects such as frame-dragging, Doppler boost, gravitational redshift, and bending light by gravity also self-irradiation result deflection. Assuming that emission is locally blackbody, we show how depends on spin hole, inclination disk, torque at inner edge disk. find effect nonzero can, good approximation, be absorbed into zero-torque model adjusting mass...
My life has been an interesting voyage. I became astronomer because could not imagine living on Earth and trying to understand how the Universe works. scientific career revolved around observing motions of stars within galaxies ...Read More
We investigate the distribution of neutron star masses in different populations binaries, employing Bayesian statistical techniques. In particular, we explore differences between sources that have experienced distinct evolutionary paths and accretion episodes. find non-recycled eclipsing high-mass binaries as well slow pulsars, which are all believed to be near their birth masses, has a mean 1.28 M_solar dispersion 0.24 M_solar. These values consistent with expectations for formation...