Browsing by Author "Sadowski, Aleksander"
Now showing items 1-15 of 15
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Energy flows in thick accretion discs and their consequences for black hole feedback
Sadowski, Aleksander; Lasota, Jean-Pierre; Abramowicz, Marek A.; Narayan, Ramesh (Oxford University Press (OUP), 2016)We study energy flows in geometrically thick accretion discs, both optically thick and thin, using general relativistic, three-dimensional simulations of black hole accretion flows. We find that for non-rotating black holes ... -
Erratum: “The Power of Imaging: Constraining the Plasma Properties of GRMHD Simulations using EHT Observatioins of SGR A*” (2015, ApJ, 799, 1)
Chan, Chi-kwan; Psaltis, Dimitrios; Özel, Feryal; Narayan, Ramesh; Sadowski, Aleksander (IOP Publishing, 2015) -
Fast Variability and Millimeter/IR Flares in GRMHD Models of Sgr A* From Strong-Field Gravitational Lensing
Chan, Chi-kwan; Psaltis, Dimitrios; Özel, Feryal; Medeiros, Lia; Marrone, Daniel; Sadowski, Aleksander; Narayan, Ramesh (IOP Publishing, 2015)We explore the variability properties of long, high cadence GRMHD simulations across the electromagnetic spectrum using an efficient, GPU-based radiative transfer algorithm. We focus on both disk- and jet-dominated simulations ... -
Global simulations of axisymmetric radiative black hole accretion discs in general relativity with a mean-field magnetic dynamo
Sadowski, Aleksander; Narayan, Ramesh; Tchekhovskoy, Alexander; Abarca, David; Zhu, Yucong; McKinney, Jonathan C. (Oxford University Press (OUP), 2014)We present a sub-grid model that emulates the magnetic dynamo operating in magnetized accretion disks. We have implemented this model in the general relativisic radiation magnetohydrodynamic (GRRMHD) code KORAL, using ... -
GRMHD simulations of magnetized advection-dominated accretion on a non-spinning black hole: role of outflows
Narayan, Ramesh; Sadowski, Aleksander; Penna, Robert Francis; Kulkarni, Akshay K. (Oxford University Press (OUP), 2012)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 of magnetic flux around the ... -
Heroic: 3D general relativistic radiative post-processor with comptonization for black hole accretion discs
Narayan, Ramesh; Zhu, Yucong; Psaltis, Dimitrios; Sadowski, Aleksander (Oxford University Press (OUP), 2016)We describe Hybrid Evaluator for Radiative Objects Including Comptonization (HEROIC), an upgraded version of the relativistic radiative post-processor code HERO described in a previous paper, but which now Includes ... -
Levitating atmospheres of Eddington-luminosity neutron stars
Wielgus, Maciek; Sadowski, Aleksander; Kluzniak, Wiodek; Abramowicz, Marek; Narayan, Ramesh (Royal Astronomical Society, 2016)We construct models of static, spherically symmetric shells supported by the radiation flux of a luminous neutron star in the Schwarzschild metric. The atmospheres are disconnected from the star and levitate above its ... -
Measuring Black Hole Spin by the Continuum-Fitting Method: Effect of Deviations from the Novikov-Thorne Disc Model
Kulkarni, Akshay K.; Penna, Robert Francis; Shcherbakov, Roman V.; Steiner, James Francis; Narayan, Ramesh; Sadowski, Aleksander; Zhu, Yucong; McClintock, Jeffrey E.; Davis, Shane W.; McKinney, Jonathan C. (Oxford University Press (OUP), 2011)The X-ray spectra of accretion discs of eight stellar mass black holes have been analysed to date using the thermal continuum-fitting method, and the spectral fits have been used to estimate the spin parameters of the black ... -
Photon-conserving Comptonization in simulations of accretion discs around black holes
Sadowski, Aleksander; Narayan, Ramesh (Oxford University Press (OUP), 2015)We introduce a new method for treating Comptonization in computational fluid dynamics. By construction, this method conserves the number of photons. Whereas the traditional “blackbody Comptonization” approach assumes that ... -
The Power of Imaging: Constraining the Plasma Properties of GRMHD Simulations Using EHY Observations of Sgr A *
Chan, Chi-Kwan; Psaltis, Dimitrios; Özel, Feryal; Narayan, Ramesh; Sadowski, Aleksander (IOP Publishing, 2015)Recent advances in general relativistic magnetohydrodynamic simulations have expanded and improved our understanding of the dynamics of black-hole accretion disks. However, current simulations do not capture the thermodynamics ... -
Powerful radiative jets in supercritical accretion discs around non-spinning black holes
Sadowski, Aleksander; Narayan, Ramesh (Oxford University Press (OUP), 2015)We describe a set of simulations of super-critical accretion onto a non-rotating supermassive BH. The accretion flow is radiation pressure dominated and takes the form of a geometrically thick disk with twin low-density ... -
The slimming effect of advection on black-hole accretion flows
Lasota, J.-P.; Vieira, Rebecca Lynn; Sadowski, A; Narayan, Ramesh; Abramowicz, M. A. (EDP Sciences, 2016)We study energy flows in geometrically thick accretion discs, both optically thick and thin, using general relativistic, three-dimensional simulations of black hole accretion flows. We find that for non-rotating black holes ... -
Stable, levitating, optically thin atmospheres of Eddington-luminosity neutron stars
Wielgus, M.; Kluźniak, W.; Sadowski, A; Narayan, Ramesh; Abramowicz, M. (Oxford University Press (OUP), 2015)In general relativity static gaseous atmospheres may be in hydrostatic balance in the absence of a supporting stellar surface, provided that the luminosity is close to the Eddington value. We construct analytic models of ... -
Testing Slim-Disk Models on the Thermal Spectra of LMC X-3
Straub, O.; Bursa, M.; Sadowski, Aleksander; Steiner, James Francis; Abramowicz, M. A.; Kluźniak, W.; McClintock, Jeffrey E.; Narayan, Ramesh; Remillard, R. A. (EDP Sciences, 2011)Slim-disk models describe advective accretion flows at high luminosities, while reducing to the standard thin disk form in the low luminosity limit. We have developed a new spectral model, slimbb, within the framework of ... -
Three-dimensional simulations of supercritical black hole accretion discs – luminosities, photon trapping and variability
Sadowski, Aleksander; Narayan, Ramesh (Oxford University Press (OUP), 2016)We present a set of four three-dimensional, general relativistic, radiation magnetohydrodynamical simulations of black hole accretion at supercritical mass accretion rates, dot{M} > dot{M}_Edd. We use these simulations to ...