Testing SgrA{sup *} with the spectrum of its accretion structure

Lin, Nan; Li, Zilong; Bambi, Cosimo; Arthur, Jake; Asquith, Rachel

doi:10.1088/1475-7516/2015/09/038

Title: Testing SgrA{sup *} with the spectrum of its accretion structure

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Abstract

SgrA{sup *} is the supermassive black hole candidate at the center of the Galaxy and an ideal laboratory to test general relativity. Following previous work by other authors, we use the Polish doughnut model to describe an optically thin and constant angular momentum ion torus in hydrodynamical equilibrium and model the accretion structure around SgrA{sup *}. The radiation mechanisms are bremsstrahlung, synchrotron emission, and inverse Compton scattering. We compute the spectrum as seen by a distant observer in Kerr and non-Kerr spacetimes and we study how an accurate measurement can constrain possible deviations form the Kerr solution. As in the case of emission from a thin accretion disk, we find a substantial degeneracy between the determination of the spin and of possible deviations from the Kerr geometry, even when the parameters of the ion torus are fixed. This means that this technique cannot independently test the nature of SgrA{sup *} even in the presence of good data and with the systematics under control. However, it might do it in combination with other measurements (black hole shadow, radio pulsar, etc.)

Authors:

Lin, Nan; Li, Zilong; Bambi, Cosimo ^[1]; Arthur, Jake; Asquith, Rachel ^[2]

Center for Field Theory and Particle Physics and Department of Physics, Fudan University, 220 Handan Road, 200433 Shanghai (China)
School of Physics and Astronomy, The University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)

Publication Date:: Tue Sep 01 00:00:00 EDT 2015

OSTI Identifier:: 22525381

Resource Type:: Journal Article

Journal Name:: Journal of Cosmology and Astroparticle Physics

Additional Journal Information:: Journal Volume: 2015; Journal Issue: 09; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1475-7516

Country of Publication:: United States

Language:: English

Subject:: 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; BLACK HOLES; BREMSSTRAHLUNG; COMPTON EFFECT; EQUILIBRIUM; GENERAL RELATIVITY THEORY; IONS; KERR METRIC; MILKY WAY; PULSARS; SPACE-TIME; SPIN; STAR ACCRETION; STAR MODELS

Citation Formats


                    Lin, Nan, Li, Zilong, Bambi, Cosimo, Arthur, Jake, and Asquith, Rachel. Testing SgrA{sup *} with the spectrum of its accretion structure.  United States: N. p., 2015. 
        Web.  doi:10.1088/1475-7516/2015/09/038.

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                    Lin, Nan, Li, Zilong, Bambi, Cosimo, Arthur, Jake, & Asquith, Rachel. Testing SgrA{sup *} with the spectrum of its accretion structure.  United States.  https://doi.org/10.1088/1475-7516/2015/09/038

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                    Lin, Nan, Li, Zilong, Bambi, Cosimo, Arthur, Jake, and Asquith, Rachel. 2015.  
        "Testing SgrA{sup *} with the spectrum of its accretion structure".  United States.  https://doi.org/10.1088/1475-7516/2015/09/038.

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@article{osti_22525381,

  title        = {Testing SgrA{sup *} with the spectrum of its accretion structure},

  author       = {Lin, Nan and Li, Zilong and Bambi, Cosimo and Arthur, Jake and Asquith, Rachel},

  abstractNote = {SgrA{sup *} is the supermassive black hole candidate at the center of the Galaxy and an ideal laboratory to test general relativity. Following previous work by other authors, we use the Polish doughnut model to describe an optically thin and constant angular momentum ion torus in hydrodynamical equilibrium and model the accretion structure around SgrA{sup *}. The radiation mechanisms are bremsstrahlung, synchrotron emission, and inverse Compton scattering. We compute the spectrum as seen by a distant observer in Kerr and non-Kerr spacetimes and we study how an accurate measurement can constrain possible deviations form the Kerr solution. As in the case of emission from a thin accretion disk, we find a substantial degeneracy between the determination of the spin and of possible deviations from the Kerr geometry, even when the parameters of the ion torus are fixed. This means that this technique cannot independently test the nature of SgrA{sup *} even in the presence of good data and with the systematics under control. However, it might do it in combination with other measurements (black hole shadow, radio pulsar, etc.)},

  doi          = {10.1088/1475-7516/2015/09/038},

  url          = {https://www.osti.gov/biblio/22525381},
  journal      = {Journal of Cosmology and Astroparticle Physics},

  issn         = {1475-7516},

  number       = 09,

  volume       = 2015,

  place        = {United States},

  year         = {Tue Sep 01 00:00:00 EDT 2015},

  month        = {Tue Sep 01 00:00:00 EDT 2015}

}

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