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Article Dans Une Revue The Astrophysical journal letters Année : 2006

A Possible Rossby Wave Instability Origin for the Flares in Sagittarius A

Michel Tagger
F. Melia
  • Fonction : Auteur

Résumé

In recent years, near-IR and X-ray flares have been detected from the Galaxy's central radio point source, Sagittarius A* (Sgr A*), believed to be a \~3.10^6 solar masses supermassive black hole. In some cases, the transient emission appears to be modulated with a (quasi-)periodic oscillation (QPO) of ~ 17-20 minutes. The implied ~ 3 r_S size of the emitter (where r_S = 2GM/c^2 is the Schwarzschild radius) points to an instability - possibly induced by accretion - near the Marginally Stable Orbit (MSO) of a slowly spinning object. But Sgr A* is not accreting via a large, 'standard' disk; instead, the low density environment surrounding it apparently feeds the black hole with low angular momentum clumps of plasma that circularize within ~ 10-300 r_S and merge onto a compact, hot disk. In this Letter, we follow the evolution of the disk following such an event, and show that a Rossby wave instability, particularly in its magnetohydrodynamic (MHD) form, grows rapidly and produces a period of enhanced accretion lasting several hours. Both the amplitude of this response, and its duration, match the observed flare characteristics rather well.

Dates et versions

in2p3-00025149 , version 1 (29-11-2005)

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Michel Tagger, F. Melia. A Possible Rossby Wave Instability Origin for the Flares in Sagittarius A. The Astrophysical journal letters, 2006, 636, pp.L33-L36. ⟨10.1086/499806⟩. ⟨in2p3-00025149⟩
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