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PAPER WITHDRAWN. The recent detection of Sgr A* in the X-ray band, together with the radio polarization measurements conducted over the past few years, offer the best constraints yet for understanding the nature of the emitting gas within…

Astrophysics · Physics 2007-05-23 Fulvio Melia , Siming Liu , Marco Fatuzzo

The gas cloud G2 falling toward Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, is supposed to provide valuable information on the physics of accretion flows and the environment of the black hole. We…

High Energy Astrophysical Phenomena · Physics 2015-04-22 J. -H. Park , S. Trippe , T. P. Krichbaum , J. -Y. Kim , M. Kino , A. Bertarini , M. Bremer , P. de Vicente

The super-massive 4 million solar mass black hole Sagittarius~A* (SgrA*) shows flare emission from the millimeter to the X-ray domain. A detailed analysis of the infrared light curves allows us to address the accretion phenomenon in a…

Viscous rotating accretion flows around black holes become advection-dominated when the accretion rate $\dot M$ is sufficiently low. Most of the accretion energy in such flows is stored within the gas and advected radially inward. The…

Astrophysics · Physics 2011-05-23 Ramesh Narayan , Insu Yi , Rohan Mahadevan

The cores of most galaxies are thought to harbour supermassive black holes, which power galactic nuclei by converting the gravitational energy of accreting matter into radiation (ref 1). Sagittarius A*, the compact source of radio, infrared…

Spectral and kinematic studies suggest that the nonthermal radio source Sgr A*, located at the center of the Milky Way, is a supermassive compact object with a mass 2-3 million solar masses. Winds from nearby stars, located approximately…

Astrophysics · Physics 2009-10-30 Robert F. Coker , F. Melia

Sgr A* is the variable electromagnetic source associated with accretion onto the Galactic center supermassive black hole. While the near-infrared (NIR) variability of Sgr A* was shown to be consistent over two decades, unprecedented…

Recent observations of Sgr A* give strong constraints for possible models of the physical nature of Sgr A* and suggest the presence of a massive black~hole with M<2 10^6 M_sun surrounded by an accretion disk which we estimate to radiate at…

Astrophysics · Physics 2011-05-23 Heino Falcke , Peter L. Biermann , Wolfgang J. Duschl , Peter G. Mezger

The extremely hot and tenuous accretion flow in the immediate vicinity of Sgr A* is believed to be invisible (too dim) in the X-ray band, except for short X-ray flares. Here we point out that during pericenter passages, close brightest…

Astrophysics · Physics 2009-11-10 Sergei Nayakshin

Ongoing millimeter VLBI observations with the Event Horizon Telescope allow unprecedented study of the innermost portion of black hole accretion flows. Interpreting the observations requires relativistic, time-dependent physical modeling.…

High Energy Astrophysical Phenomena · Physics 2015-06-04 Jason Dexter , Eric Agol , P. Chris Fragile , Jonathan C. McKinney

The massive black hole in our galactic center, Sgr A*, accretes only a small fraction of the gas available at its Bondi radius. The physical processes determining this accretion rate remain unknown, partly due to a lack of observational…

High Energy Astrophysical Phenomena · Physics 2015-03-18 Michael McCourt , Ann-Marie Madigan

A supermassive black hole SgrA* with the mass ~4x10^6 Msun resides at the centre of our galaxy. Building up such a massive black hole within the ~10^10 year lifetime of our galaxy would require a mean accretion rate of ~4x10^-4 Msun/yr. At…

Astrophysics of Galaxies · Physics 2019-06-21 Elena M. Murchikova , E. Sterl Phinney , Anna Pancoast , Roger D. Blandford

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 image of the emission surrounding the black hole in the center of the Milky Way is predicted to exhibit the imprint of general relativistic (GR) effects, including the existence of a shadow feature and a photon ring of diameter ~50…

Recent observations of the radio and NIR source Sgr A* reinforce the interpretation of the Galactic Center as a scaled down version of an AGN. The discovery of an elongated structure at 43 GHz and increasing evidence for the presence of an…

Astrophysics · Physics 2011-05-23 Heino Falcke , Karl Mannheim , Peter L. Biermann

In this paper the jet model for the supermassive black hole candidate Sgr A* in the Center of the Galaxy is reviewed. The most recent model, with a reduced set of parameters, is able to account for all major radio properties of the source:…

Astrophysics · Physics 2007-05-23 Heino Falcke

Stars orbiting within 1$\arcsec$ of the supermassive black hole in the Galactic Centre, Sgr A*, are notoriously difficult to detect due to obscuration by gas and dust. We show that some stars orbiting this region may be detectable via…

Astrophysics of Galaxies · Physics 2015-10-28 Idan Ginsburg , Xiawei Wang , Abraham Loeb , Ofer Cohen

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

At the center of the Milky Way lurks a unique compact nonthermal radio source, Sgr A*. It is thought to be powered by a 2.6 million solar mass black hole that is accreting the stellar winds from the numerous early-type stars that exist in…

Astrophysics · Physics 2007-05-23 R. F. Coker , S. Markoff

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