Browsing by Author "Sadowski, Aleksander"
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Energy flows in thick accretion discs and their consequences for black hole feedback
Sadowski, Aleksander; Lasota, JeanPierre; 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, threedimensional simulations of black hole accretion flows. We find that for nonrotating 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, Chikwan; Psaltis, Dimitrios; Özel, Feryal; Narayan, Ramesh; Sadowski, Aleksander (IOP Publishing, 2015) 
Fast Variability and Millimeter/IR Flares in GRMHD Models of Sgr A* From StrongField Gravitational Lensing
Chan, Chikwan; 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, GPUbased radiative transfer algorithm. We focus on both disk and jetdominated simulations ... 
Global simulations of axisymmetric radiative black hole accretion discs in general relativity with a meanfield magnetic dynamo
Sadowski, Aleksander; Narayan, Ramesh; Tchekhovskoy, Alexander; Abarca, David; Zhu, Yucong; McKinney, Jonathan C. (Oxford University Press (OUP), 2014)We present a subgrid 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 advectiondominated accretion on a nonspinning 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 longduration GRMHD simulations of advectiondominated accretion around a nonspinning black hole. The first simulation was designed to avoid significant accumulation of magnetic flux around the ... 
Heroic: 3D general relativistic radiative postprocessor 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 postprocessor code HERO described in a previous paper, but which now Includes ... 
Levitating atmospheres of Eddingtonluminosity 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 ContinuumFitting Method: Effect of Deviations from the NovikovThorne 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 Xray spectra of accretion discs of eight stellar mass black holes have been analysed to date using the thermal continuumfitting method, and the spectral fits have been used to estimate the spin parameters of the black ... 
Photonconserving 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, ChiKwan; 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 blackhole accretion disks. However, current simulations do not capture the thermodynamics ... 
Powerful radiative jets in supercritical accretion discs around nonspinning black holes
Sadowski, Aleksander; Narayan, Ramesh (Oxford University Press (OUP), 2015)We describe a set of simulations of supercritical accretion onto a nonrotating supermassive BH. The accretion flow is radiation pressure dominated and takes the form of a geometrically thick disk with twin lowdensity ... 
The slimming effect of advection on blackhole 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, threedimensional simulations of black hole accretion flows. We find that for nonrotating black holes ... 
Stable, levitating, optically thin atmospheres of Eddingtonluminosity 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 SlimDisk Models on the Thermal Spectra of LMC X3
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)Slimdisk 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 ... 
Threedimensional 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 threedimensional, general relativistic, radiation magnetohydrodynamical simulations of black hole accretion at supercritical mass accretion rates, dot{M} > dot{M}_Edd. We use these simulations to ...