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Title: The intrinsic two-dimensional size of Sagittarius A*

We report the detection of the two-dimensional structure of the radio source associated with the Galactic Center black hole, Sagittarius A*, obtained from Very Long Baseline Array observations at a wavelength of 7 mm. The intrinsic source is modeled as an elliptical Gaussian with major-axis size 35.4 × 12.6 R{sub S} in position angle 95° east of north. This morphology can be interpreted in the context of both jet and accretion disk models for the radio emission. There is supporting evidence in large angular-scale multi-wavelength observations for both source models for a preferred axis near 95°. We also place a maximum peak-to-peak change of 15% in the intrinsic major-axis size over five different epochs. Three observations were triggered by detection of near infrared (NIR) flares and one was simultaneous with a large X-ray flare detected by NuSTAR. The absence of simultaneous and quasi-simultaneous flares indicates that not all high energy events produce variability at radio wavelengths. This supports the conclusion that NIR and X-ray flares are primarily due to electron excitation and not to an enhanced accretion rate onto the black hole.
Authors:
 [1] ;  [2] ; ;  [3] ;  [4] ;  [5] ; ;  [6] ; ; ; ;  [7]
  1. Academica Sinica Institute of Astronomy and Astrophysics (ASIAA), 645 North A'ohoku Place, Hilo, HI 96720 (United States)
  2. Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098XH Amsterdam (Netherlands)
  3. Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany)
  4. Radio Astronomy Laboratory, UC Berkeley, B-20 Hearst Field Annex, Berkeley, CA 94720-3411 (United States)
  5. Department of Physics and Astronomy, Wheaton College, Norton, MA 02766 (United States)
  6. AstroParticule et Cosmologie (APC), Université Paris 7 Denis Diderot, F-75205 Paris cedex 13 (France)
  7. UCLA Division of Astronomy and Astrophysics, Los Angeles, CA 90095-1562 (United States)
Publication Date:
OSTI Identifier:
22365630
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 790; Journal Issue: 1; 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; DETECTION; EMISSION; EXCITATION; GALAXIES; GALAXY NUCLEI; NEAR INFRARED RADIATION; TWO-DIMENSIONAL CALCULATIONS; WAVELENGTHS; X RADIATION