A possible rossby wave instability origin for the flares in sagittarius A

Michel Tagger, Fulvio Melia

Research output: Contribution to journalReview articlepeer-review

75 Scopus citations


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 an ∼3 × 106 M 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 ∼3rs size of the emitter (where rs ≡ 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)rs and merge onto a compact, hot disk. In this Letter, we follow the evolution of the disk following such an event, and we 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.

Original languageEnglish (US)
Pages (from-to)L33-L36
JournalAstrophysical Journal
Issue number1 II
StatePublished - Jan 1 2006


  • Accretion, accretion disks
  • Black hole physics
  • Galaxy: center
  • Instabilities
  • MHD
  • Plasmas

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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