2013/07/23 by Daryl Haggard, Adrienne M. Cool, Craig O. Heinke +4 · 2 citations
Physics and Astronomy · #Accretion (finance) #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Galactic Center #Galaxies: Formation, Evolution, Phenomena #Intermediate-mass black hole #Luminosity #Observatory #Omega #Supermassive black hole #astro-ph.GA #astro-ph.HE
paper · pdf · doi:10.1088/2041-8205/773/2/l31
6 pages, 3 figures, Accepted to ApJ Letters
arxiv created 2013/07/23 · openalex publication_date 2013/08/06 · arxiv updated 2015/06/16 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We report a sensitive X-ray search for the proposed intermediate-mass black hole (IMBH) in the massive Galactic cluster, ω Centauri (NGC 5139). Combining Chandra X-ray Observatory data from Cycles 1 and 13, we obtain a deep (∼291 ks) exposure of the central regions of the cluster. We find no evidence for an X-ray point source near any of the cluster's proposed dynamical centers, and place an upper limit on the X-ray flux from a central source of f X (0.5–7.0 keV) ⩽5.0 × 10 −16 erg cm −2 s −1 , after correcting for absorption. This corresponds to an unabsorbed X-ray luminosity of L X (0.5–7.0 keV) ⩽1.6 × 10 30 erg s −1 , for a cluster distance of 5.2 kpc, Galactic column density N H = 1.2 × 10 21 cm −2 , and power-law spectrum with Γ = 2.3. If a ∼10 4 IMBH resides in the cluster's core, as suggested by some stellar dynamical studies, its Eddington luminosity would be L Edd ∼10 42 erg s −1 . The new X-ray limit would then establish an Eddington ratio of L X / L Edd ≲ 10 −12 , a factor of ∼10 lower than even the quiescent state of our Galaxy's notoriously inefficient supermassive black hole Sgr A*, and imply accretion efficiencies as low as η ≲ 10 −6 –10 −8 . This study leaves open three possibilities: either ω Cen does not harbor an IMBH or, if an IMBH does exist, it must experience very little or very inefficient accretion.