The galactic center weather forecast

M. Mościbrodzka, H. Shiokawa, C. F. Gammie, J. C. Dolence

Research output: Contribution to journalArticlepeer-review


In accretion-based models for Sgr A*, the X-ray, infrared, and millimeter emission arise in a hot, geometrically thick accretion flow close to the black hole. The spectrum and size of the source depend on the black hole mass accretion rate Ṁ. Since Gillessen et al. have recently discovered a cloud moving toward Sgr A*. that will arrive in summer 2013,Ṁ may increase from its present valueṀ0. We therefore reconsider the "best-bet" accretion model of Móscibrodzka et al., which is based on a general relativistic MHD flow model and fully relativistic radiative transfer, for a range of Ṁ. We find that for modest increases in Ṁ the characteristic ring of emission due to the photon orbit becomes brighter, more extended, and easier to detect by the planned Event Horizon Telescope submillimeter Very Long Baseline Interferometry experiment. If Ṁ≳ 8Ṁ0, this "silhouette" of the black hole will be hidden beneath the synchrotron photosphere at 230 GHz, and for Ṁ ≳ 16Ṁ0 the silhouette is hidden at 345 GHz. We also find that forṀ > 2Ṁ0 the near-horizon accretion flow becomes a persistent X-ray and mid-infrared source, and in the near-infrared Sgr A* will acquire a persistent component that is brighter than currently observed flares.

Original languageEnglish (US)
Article numberL1
JournalAstrophysical Journal Letters
Issue number1
StatePublished - Jun 10 2012


  • Galaxy: center

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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