The nucleus of M31

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15 Scopus citations


High-resolution measurements of the rapid rotation and large velocity dispersion in the nucleus of the Andromeda nebula (M31) hint at the possible influence of a massive black hole in that region. The recent detection of an unresolved radio source coincident with the dynamical center of the galaxy has evoked a direct comparison of M31's nucleus with the compact, nonthermal radio source Sgr A* at the center of our own Galaxy. We calculate the broad-band spectrum expected of a 107 M black hole accreting from an ambient galactic wind in the nucleus of M31, and we discuss several testable predictions of this model: (1) when resolved, this source will probably be elongated, perhaps in the direction of the semistellar nucleus BD +40° 148; (2) its radio spectral index is expected to be ∼0.4 (compared with ∼0.25 for Sgr A*); (3) the radio component should steepen sharply between ∼1010 and 1011 Hz; (4) if an association between this radio source and a nearby Einstein X-ray source is confirmed, its radio luminosity should be variable on a time of ≲1 yr; and (5) the variability of its radio and X-ray fluxes should be anticorrelated.

Original languageEnglish (US)
Pages (from-to)L95-L98
JournalAstrophysical Journal
Issue number2 PART 2
StatePublished - Oct 20 1992


  • Black hole physics
  • Galaxies: individual: M31
  • Galaxies: nuclei
  • Stars: mass loss
  • X-rays: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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