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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)…

High Energy Astrophysical Phenomena · Physics 2025-02-06 León Salas , Matthew Liska , Sera Markoff , Koushik Chatterjee , Gibwa Musoke , Oliver Porth , Bart Ripperda , Doosoo Yoon , Wanga Mulaudzi

The accretion flow around the Galactic Center black hole Sagittarius A* (Sgr A*) is expected to have an electron temperature that is distinct from the ion temperature, due to weak Coulomb coupling in the low-density plasma. We present four…

High Energy Astrophysical Phenomena · Physics 2018-05-31 Andrew Chael , Michael E. Rowan , Ramesh Narayan , Michael D. Johnson , Lorenzo Sironi

We present the first spectral energy distributions produced self-consistently by 2.5D general relativistic magneto-hydrodynamical (GRMHD) numerical simulations, where radiative cooling is included in the dynamical calculation. As a case…

High Energy Astrophysical Phenomena · Physics 2015-06-11 Samia Drappeau , Salomé Dibi , Jason Dexter , Sera Markoff , P. Chris Fragile

Sagittarius A* is a compact radio source at the Galactic center, powered by accretion of fully ionized plasmas into a supermassive black hole. However, the radio emission cannot be produced through the thermal synchrotron process by a…

High Energy Astrophysical Phenomena · Physics 2009-04-02 Kyle W. Martin , Siming Liu , Chris Fragile , Cong Yu , Chris L. Fryer

The Galactic center black hole candidate Sgr A* is the best target for studies of low-luminosity accretion physics, including with near-infrared and submillimeter wavelength long baseline interferometry experiments. Here we compare images…

We present general relativistic magnetohydrodynamic (GRMHD) numerical simulations of the accretion flow around the supermassive black hole in the Galactic centre, Sagittarius A* (Sgr A*). The simulations include for the first time radiative…

High Energy Astrophysical Phenomena · Physics 2015-06-05 Salomé Dibi , Samia Drappeau , P. Chris Fragile , Sera Markoff , Jason Dexter

We present ALMA observations at 233, 678, and 870 GHz of the Galactic Center black hole, Sagittarius A*. These observations reveal a flat spectrum over this frequency range with spectral index $\alpha \approx -0.3$, where the flux density…

We present results of simulations of the spectrum of the accretion flow onto the supermassive black hole in our Galactic Centre, Sagittarius A*, generated with a coupling of Monte-Carlo (MC) radiation and general relativistic…

High Energy Astrophysical Phenomena · Physics 2015-05-14 Guy Hilburn , Edison Liang , Siming Liu , Hui Li

In this paper, we provide a first physical interpretation for the Event Horizon Telescope (EHT)'s 2017 observations of Sgr A*. Our main approach is to compare resolved EHT data at 230 GHz and unresolved non-EHT observations from radio to…

High Energy Astrophysical Phenomena · Physics 2023-11-17 The Event Horizon Telescope Collaboration

We review results from general relativistic axisymmetric magnetohydrodynamic simulations of accretion in Sgr A*. We use general relativistic radiative transfer methods and to produce a broad band (from millimeter to gamma-rays) spectrum.…

High Energy Astrophysical Phenomena · Physics 2010-02-08 M. Moscibrodzka , C. F. Gammie , J. Dolence , H. Shiokawa , P. K. Leung

Wind-fed models offer a unique way to form predictive models of the accretion flow surrounding Sagittarius A*. We present 3D, wind-fed MHD and GRMHD simulations spanning the entire dynamic range of accretion from parsec scales to the event…

High Energy Astrophysical Phenomena · Physics 2023-03-29 Sean M. Ressler , Christopher J. White , Eliot Quataert

This work proposes a methodology to test phenomenologically-motivated emission processes that account for the flux and polarization distribution and global structure of the 230 GHz sources imaged by the Event Horizon Telescope (EHT):…

The radio source Sagittarius A* (Sgr A*) is believed to be a hot, inhomogeneous, magnetized plasma flowing near the event horizon of the 3 million solar mass black hole at the galactic center. At a distance of 8000 parsecs the black hole…

Astrophysics · Physics 2008-11-26 Scott C. Noble , Po Kin Leung , Charles F. Gammie , Laura G. Book

We obtain estimates of Sgr A* accretion flow and black hole parameters by fitting polarized sub-mm observations with spectra computed using three-dimensional (3D) general relativistic (GR) magnetohydrodynamical (MHD) (GRMHD) simulations.…

High Energy Astrophysical Phenomena · Physics 2015-05-19 Roman V. Shcherbakov , Robert F. Penna , Jonathan C. McKinney

Sagittarius A* exhibits regular variability in its multiwavelength emission, including daily X-ray flares and roughly continuous near-infrared (NIR) flickering. The origin of this variability is still ambiguous since both inverse Compton…

The $230$ GHz lightcurves of Sagittarius~A* (Sgr~A*) predicted by general relativistic magnetohydrodynamics (GRMHD) and ray-tracing (GRRT) models in Event Horizon Telescope Collaboration et al. (2022) have higher variability $M_{\Delta T}$…

High Energy Astrophysical Phenomena · Physics 2024-02-06 Ho-Sang Chan , Chi-kwan Chan , Ben S. Prather , George N. Wong , Charles Gammie

Using flow models based on axisymmetric general relativistic magnetohydrodynamics (GRMHD) simulations, we construct radiative models for sgr A*. Spectral energy distributions that include the effects of thermal synchrotron emission and…

High Energy Astrophysical Phenomena · Physics 2014-11-20 Monika Moscibrodzka , Charles F. Gammie , Joshua C. Dolence , Hotaka Shiokawa , Po Kin Leung

General Relativistic Magnetohydrodynamics (GRMHD) simulations are an indispensable tool in studying accretion onto compact objects. The Event Horizon Telescope (EHT) frequently uses libraries of ideal GRMHD simulations to interpret…

High Energy Astrophysical Phenomena · Physics 2025-01-27 Vedant Dhruv , Ben Prather , George Wong , Charles F. Gammie

Recent high resolution observations of the Galactic center black hole allow for direct comparison with accretion disk simulations. We compare two-temperature synchrotron emission models from three dimensional, general relativistic…

High Energy Astrophysical Phenomena · Physics 2010-10-26 Jason Dexter , Eric Agol , P. Chris Fragile , Jonathan C. McKinney

We revisit the radiative properties of 3D general relativistic magnetohydrodynamics (GRMHD) two-temperature magnetically arrested disk (MAD) models in which electrons are heated by a magnetic turbulent cascade. We focus on studying the…

High Energy Astrophysical Phenomena · Physics 2025-02-17 M. Moscibrodzka
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