2008/03/31 by Jifeng Liu, Jeffrey E. McClintock, Jeffery E. McClintock +3 · 9 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Galaxies: Formation, Evolution, Phenomena #astro-ph
paper · pdf · doi:10.1086/588840
published as The Astrophysical Journal, 679, L37-L40, 2008 May 20 · 14 pages, 3 figures, 1 table, published in ApJ Letters; as explained in the erratum at the end of the text, the spin parameter has been corrected upward from a*=0.77 to a*=0.84. Apart from the addition of the erratum, the paper is unchanged.
openalex publication_date 2008/04/21 · arxiv created 2010/05/11 · arxiv updated 2010/05/13 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
In prior work, Chandra and Gemini-North observations of the eclipsing X-ray binary M33 X-7 have yielded measurements of the mass of its black hole primary and the system's orbital inclination angle of unprecedented accuracy. Likewise, the distance to the binary is known to a few percent. In an analysis based on these precise results, 15 Chandra and XMM-Newton X-ray spectra, and our fully relativistic accretion disk model, we find that the dimensionless spin parameter of the black hole primary is a * = 0.77 ± 0.05. The quoted 1 σ error includes all sources of observational uncertainty. Four Chandra spectra of the highest quality, which were obtained over a span of several years, all lead to the same estimate of spin to within statistical errors (2%), and this estimate is confirmed by 11 spectra of lower quality. There are two remaining uncertainties: (1) the validity of the relativistic model used to analyze the observations, which is being addressed in ongoing theoretical work; and (2) our assumption that the black hole spin is approximately aligned with the angular momentum vector of the binary, which can be addressed by a future X-ray polarimetry mission.