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| Paper: |
Intrinsic Size and Shape of SGR A*: 3.6 AU by <1 AU |
| Volume: |
186, The Central Parsecs of the Galaxy |
| Page: |
72 |
| Authors: |
Lo, K. Y.; Shen, Z.; Zhao, J.-H.; Ho, P. T. P. |
| Abstract: |
By means of near-simultaneous multi-wavelength VLBA measurements, we determine for the first time the intrinsic size of Sgr A* to be 3.6 AU by < 1 AU or 72 Rsc(star) by < 20 Rsc(star), with the major axis oriented essentially north-south, where Rsc(star) ≡ ~7.5 times 1011 cm is the Schwarzschild radius for a 2.5 times 106 Modot black hole. Contrary to previous expectation that the intrinsic structure of Sgr A* is observable only at λ <= 1 mm, we can discern the intrinsic source size at λ 7 mm because (1) the scattering size along the minor axis is half that along the major axis, and (2) the near simultaneous multi-wavelength mapping of Sgr A* makes it possible to extrapolate precisely the minor axis scattering angle at λ 7 mm. The intrinsic size and shape place direct constraints on the various theoretical models for Sgr A*. |
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