A determination of the mass of Sagittarius A * from its radio spectral and source size measurements

Fulvio Melia, J. R. Jokipil, Ajay Narayanan

Research output: Contribution to journalArticlepeer-review

35 Scopus citations


There is growing evidence that Sgr A* may be a million solar mass black hole accreting from the Galactic center wind. A consideration of the spectral and source size characteristics associated with this process can offer at least two distinct means of inferring the mass M, complementing the more traditional dynamical arguments. We show that M is unmistakably correlated with both the radio spectral index and the critical wave-length below which the intrinsic source size dominates over the angular broadening due to scattering in the interstellar medium. Current observations can already rule out a mass much in excess of 2 × 106 M and suggest a likely value close to 1 × 106 M, in agreement with an earlier study matching the radio and highenergy spectral components. We anticipate that such a mass may be confirmed with the next generation of source-size observations using milliarcsecond angular resolution at 0.5-1 cm wavelengths.

Original languageEnglish (US)
Pages (from-to)L87-L90
JournalAstrophysical Journal
Issue number2 PART 2
StatePublished - Aug 20 1992


  • Accretion
  • Black hole physics
  • Galaxy center
  • Radiation mechanisms: bremsstrahlung
  • Radiation mechanisms: cyclotron and synchrotron
  • Radio continuum: galaxies
  • Stars: mass loss

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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