The intrinsic two-dimensional size of Sagittarius A*
- Academica Sinica Institute of Astronomy and Astrophysics (ASIAA), 645 North A'ohoku Place, Hilo, HI 96720 (United States)
- Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098XH Amsterdam (Netherlands)
- Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany)
- Radio Astronomy Laboratory, UC Berkeley, B-20 Hearst Field Annex, Berkeley, CA 94720-3411 (United States)
- Department of Physics and Astronomy, Wheaton College, Norton, MA 02766 (United States)
- AstroParticule et Cosmologie (APC), Université Paris 7 Denis Diderot, F-75205 Paris cedex 13 (France)
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.
- OSTI ID:
- 22365630
- Journal Information:
- Astrophysical Journal, Vol. 790, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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