Article

Testing the Radiatively Inefficient Accretion Flow Model for Sagittarius A* Using the Size Measurements

The Astrophysical Journal (Impact Factor: 6.73). 12/2008; 642(1):L45. DOI: 10.1086/504475
Source: arXiv

ABSTRACT Recent radio observations by the Very Long Baseline Array at 7 and 3.5 mm produced the high-resolution images of the compact radio source located at the center of our Galaxy (Sgr A*) and detected its wavelength-dependent intrinsic sizes at the two wavelengths. This provides us with a good chance of testing previously proposed theoretical models for Sgr A*. In this Letter, we calculate the size based on the radiatively inefficient accretion flow (RIAF) model proposed by Yuan, Quataert, & Narayan. We find that after taking into account the scattering of the interstellar electrons, the predicted sizes are consistent with the observations. We further predict an image of Sgr A* at 1.3 mm that can be tested by future observations.

0 Bookmarks
 · 
63 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In May 2007 the compact radio source Sgr A* was observed in a global multi-frequency monitoring campaign, from radio to X-ray bands. Here we present and discuss first and preliminary results from polarization sensitive VLBA observations, which took place during May 14-25, 2007. Here, Sgr A* was observed in dual polarization on 10 consecutive days at 22, 43, and 86 GHz. We describe the VLBI experiments, our data analysis, monitoring program and show preliminary images obtained at the various frequencies. We discuss the data with special regard also to the short term variability.
    Journal of Physics Conference Series 09/2008; 131(1).
  • [Show abstract] [Hide abstract]
    ABSTRACT: We explore the time evolution of radiatively-inefficient accretion flows. Since these types of accretion flows are convectively unstable, we also study the effects of convection in the present model. The effects of convection are applied to equations describing angular momentum and energy. In analogy to the traditional α-prescription, we introduce the convection parameter αc to study the influences of convection on physical quantities. The model is studied in two cases: the transport of angular momentum due to convection inward and outward. We found the physical variables are sensitive to the parameter αc and are also dependent on the direction of angular momentum that is transported by convection. As for angular momentum transfer inward, the accretion flow can be convectively dominated and radial infall velocity becomes zero. Moreover, we found the radial dependence of the density and radial velocity takes an intermediate place between steady state radiatively-inefficient accretion flow and steady state advection-dominated accretion flow. This property is in accord with direct numerical simulation of radiatively-inefficient accretion flows.
    Research in Astronomy and Astrophysics 09/2013; 13(9):1075. · 1.35 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The center of our Galaxy hosts the best constrained supermassive black hole in the universe, Sagittarius A* (Sgr A*). Its mass and distance have been accurately determined from stellar orbits and proper motion studies, respectively, and its high-frequency radio, and highly variable near-infrared and X-ray emission originate from within a few Schwarzschild radii of the event horizon. The theory of general relativity (GR) predicts the appearance of a black hole shadow, which is a lensed image of the event horizon. This shadow can be resolved by very long baseline radio interferometry and test basic predictions of GR and alternatives thereof. In this paper we review our current understanding of the physical properties of Sgr A*, with a particular emphasis on the radio properties, the black hole shadow, and models for the emission and appearance of the source. We argue that the Galactic Center holds enormous potential for experimental tests of black hole accretion and theories of gravitation in their strong limits.
    Classical and Quantum Gravity 11/2013; 30(24). · 3.56 Impact Factor

Full-text (2 Sources)

Download
1 Download
Available from