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Title: THE X-RAY FLUX DISTRIBUTION OF SAGITTARIUS A* AS SEEN BY CHANDRA

We present a statistical analysis of the X-ray flux distribution of Sgr A* from the Chandra X-Ray Observatory's 3 Ms Sgr A* X-ray Visionary Project in 2012. Our analysis indicates that the observed X-ray flux distribution can be decomposed into a steady quiescent component, represented by a Poisson process with rate Q = (5.24 ± 0.08) × 10{sup –3} counts s{sup –1}, and a variable component, represented by a power law process (dN/dF∝F {sup –ξ}, ξ=1.92{sub −0.02}{sup +0.03}). This slope matches our recently reported distribution of flare luminosities. The variability may also be described by a log-normal process with a median unabsorbed 2-8 keV flux of 1.8{sub −0.6}{sup +0.8}×10{sup −14} erg s{sup –1} cm{sup –2} and a shape parameter σ = 2.4 ± 0.2, but the power law provides a superior description of the data. In this decomposition of the flux distribution, all of the intrinsic X-ray variability of Sgr A* (spanning at least three orders of magnitude in flux) can be attributed to flaring activity, likely in the inner accretion flow. We confirm that at the faint end, the variable component contributes ∼10% of the apparent quiescent flux, as previously indicated by our statistical analysis of X-ray flares in these Chandra observations. Our flux distribution provides a newmore » and important observational constraint on theoretical models of Sgr A*, and we use simple radiation models to explore the extent to which a statistical comparison of the X-ray and infrared can provide insights into the physics of the X-ray emission mechanism.« less
Authors:
 [1] ;  [2] ; ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9] ;  [10] ;  [11] ;  [12] ;  [13]
  1. Department of Astronomy, Boston University, Boston, MA 02215 (United States)
  2. Astronomical Institute, "Anton Pannekoek," University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands)
  3. MIT Kavli Institute for Astrophysics and Space Research, Cambridge, MA 02139 (United States)
  4. Department of Astronomy, Hearst Field Annex, University of California, Berkeley, CA 94720-3411 (United States)
  5. Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547 (United States)
  6. Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450 (United States)
  7. Department of Astronomy and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen, Fujian 361005 (China)
  8. Institute of Astronomy, University of Cambridge, Cambridge, CB3 OHA (United Kingdom)
  9. Department of Physics and Astronomy, College of Charleston, Charleston, SC 29424 (United States)
  10. Department of Astronomy, University of Illinois Urbana-Champaign, 1002 West Green Street, Urbana, IL 61801 (United States)
  11. AstroParticule et Cosmologie (APC), Université Paris 7 Denis Diderot, F-75205 Paris cedex 13 (France)
  12. Observatoire Astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l'Université, F-67000 Strasbourg (France)
  13. Department of Physics and Astronomy, AC# 2244, Amherst College, Amherst, MA 01002 (United States)
Publication Date:
OSTI Identifier:
22364327
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 799; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; BLACK HOLES; COMPARATIVE EVALUATIONS; KEV RANGE; LIMITING VALUES; PHOTON EMISSION; STAR MODELS; STELLAR FLARES; X RADIATION