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In this paper we review and discuss some of the intriguing properties of the Galactic Center supermassive black hole candidate Sgr A*. Of all possible black hole sources, the event horizon of Sgr A*, subtends the largest angular scale on…

High Energy Astrophysical Phenomena · Physics 2015-05-20 Heino Falcke , Sera Markoff , Geoffrey C. Bower , Charles F. Gammie , Monika Moscibrodzka , Dipankar Maitra

The near-infrared emission from the black hole at the Galactic center (Sgr A*) has unique properties. The most striking feature is a suggestive periodic sub-structure that has been observed in a couple of flares so far. Using near-infrared…

Astrophysics · Physics 2009-11-13 L. Meyer , R. Schoedel , A. Eckart , W. J. Duschl , V. Karas , M. Dovciak

High resolution observations of Sgr A* have revealed a wide variety of phenomena, ranging from intense rapid flares to quasi-periodic oscillations, making this object an ideal system to study the properties of low luminosity accreting black…

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 calculate the radiative properties of Sagittarius A* -- spectral energy distribution, variability, and radio-infrared images -- using the first 3D, physically motivated black hole accretion models that directly evolve the electron…

High Energy Astrophysical Phenomena · Physics 2017-03-22 Sean M. Ressler , Alexander Tchekhovskoy , Eliot Quataert , Charles F. Gammie

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

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 nature of the emission region around Sagittarius A* (Sgr A*), the supermassive black hole at the Galactic Center, remains under debate. A prediction of jet models is that a frequency-dependent shift in the position of the radio core…

High Energy Astrophysical Phenomena · Physics 2026-02-11 R. Fraga-Encinas , M. Moscibrodzka , H. Falcke

(abridged) The connection between black hole, accretion disk, and radio jet can be best constrained by fitting models to observations of nearby low luminosity galactic nuclei, in particular the well studied sources Sgr~A* and M87. There has…

High Energy Astrophysical Phenomena · Physics 2016-05-02 Monika Moscibrodzka , Heino Falcke , Hotaka Shiokawa

The preliminary detection of the Galactic Center black hole Sgr A* in X-rays by the Chandra mission, as well as recent mm-VLBI measurements, impose strict constraints on this source. Using a relativistic jet model for Sgr A*, we calculate…

Astrophysics · Physics 2011-05-05 Heino Falcke , Sera Markoff

The compact, nonthermal radio source Sgr A* at the Galactic Center appears to be coincident with a 2.6 million solar mass point-like object. Its energy source may be the release of gravitational energy as gas from the interstellar medium…

Astrophysics · Physics 2009-10-31 Robert F. Coker , Fulvio Melia

Sagittarius A* exhibits frequent flaring activity across the electromagnetic spectrum. Signatures of an orbiting hot spot have been identified in the polarized millimeter wavelength light curves observed with ALMA in 2017 immediately after…

High Energy Astrophysical Phenomena · Physics 2024-03-29 A. I. Yfantis , M. A. Mościbrodzka , M. Wielgus , J. T. Vos , A. Jimenez-Rosales

Intense flaring events in the near-infrared and X-ray wavebands of our Galactic Center have been the subject of research for decades. In recent years, the GRAVITY instrument of the Very Large Telescope captured the motion and polarimetric…

High Energy Astrophysical Phenomena · Physics 2024-10-16 Eleni Antonopoulou , Antonios Nathanail

Based on Bremer et al. (2011) and Eckart et al. (2012) we report on simultaneous observations and modeling of the millimeter, near-infrared, and X-ray flare emission of the source Sagittarius A* (SgrA*) associated with the super-massive…

We present the combination of dynamical accretion model based on 3D GRMHD simulations and general relativistic (GR) polarized radiative transfer. We write down the formalism of and perform the GR ray-tracing of cyclo-synchrotron radiation…

High Energy Astrophysical Phenomena · Physics 2009-12-14 Roman V. Shcherbakov , Robert F. Penna

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 with…

High Energy Astrophysical Phenomena · Physics 2015-10-21 Chi-kwan Chan , Dimitrios Psaltis , Feryal Ozel , Lia Medeiros , Daniel Marrone , Aleksander Sadowski , Ramesh Narayan

By solving radiative transfer equations, we examine three-dimensional radiative properties of a magnetohydrodynamic accretion flow model confronting with the observed spectrum of Sgr A*, in the vicinity of supermassive black hole at the…

Astrophysics of Galaxies · Physics 2015-05-13 Y. Kato , M. Umemura , K. Ohsuga

Sgr A*, the supermassive black hole (SMBH) at the center of our Milky Way Galaxy, is known to be a variable source of X-ray, near-infrared (NIR), and submillimeter (submm) radiation and therefore a prime candidate to study the…

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

Radiatively inefficient accretion flows (RIAFs) are believed to power supermassive black holes (SMBH) in the underluminous cores of galaxies. Such black holes are typically accompanied by flat-spectrum radio cores indicating the presence of…

High Energy Astrophysical Phenomena · Physics 2014-10-08 Monika Moscibrodzka , Heino Falcke , Hotaka Shiokawa , Charles F. Gammie