X-ray and radio variability of M31*, the andromeda galaxy nuclear supermassive black hole

Michael R. Garcia, Richard Hextall, Frederick K. Baganoff, Jose Galache, Fulvio Melia, Stephen S. Murray, F. A. Primini, Lornt O. Sjouwerman, Ben Williams

Research output: Contribution to journalArticlepeer-review

32 Scopus citations


We confirm our earlier tentative detection of M31* in X-rays and measure its light curve and spectrum. Observations in 2004-2005 find M31* rather quiescent in the X-ray and radio. However, X-ray observations in 2006-2007 show M31* to be highly variable at times. A separate variable X-ray source is found near P1, the brighter of the two optical nuclei. The apparent angular Bondi radius of M31* is the largest of any black hole and large enough to be well resolved with Chandra. The diffuse emission within this Bondi radius is found to have an X-ray temperature ∼ 0.3keV and density 0.1 cm-3, indistinguishable from the hot gas in the surrounding regions of the bulge given the statistics allowed by the current observations. The X-ray source at the location of M31* is consistent with a point source and a power-law spectrum with energy slope 0.9 ± 0.2. Our identification of this X-ray source with M31* is based solely on positional coincidence.

Original languageEnglish (US)
Pages (from-to)755-763
Number of pages9
JournalAstrophysical Journal
Issue number1
StatePublished - 2010


  • Accretion, accretion disks
  • Black hole physics
  • Galaxies: individual (M31)
  • Galaxies: nuclei

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'X-ray and radio variability of M31*, the andromeda galaxy nuclear supermassive black hole'. Together they form a unique fingerprint.

Cite this