2011/06/22 by Michael Koss, Richard Mushotzky, Ezequiel Treister +6 · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Galaxies: Formation, Evolution, Phenomena #astro-ph.CO #astro-ph.GA #astro-ph.HE
paper · pdf · doi:10.1088/2041-8205/735/2/l42
published as Michael Koss et al. 2011 ApJ 735 L42 · 7 pages, 5 figures, Published in Astrophysical Journal Letters. Reformatted and fixed typos in v1
openalex publication_date 2011/06/22 · arxiv created 2011/07/07 · arxiv updated 2011/07/08 · openalex created_date 2019/06/27 · openalex updated_date 2026/07/31
We have discovered a binary active galactic nucleus (AGN) in the galaxy Mrk 739 using Chandra and Swift BAT. We find two luminous ( L 2–10 keV = 1.1 × 10 43 and 1.0 × 10 42 erg s −1 ), unresolved nuclei with a projected separation of 3.4 kpc (5 8 ± 0 1) coincident with two bulge components in the optical image. The western X-ray source (Mrk 739W) is highly variable ( × 2.5) during the 4 hr Chandra observation and has a very hard spectrum consistent with an AGN. While the eastern component was already known to be an AGN based on the presence of broad optical recombination lines, Mrk 739W shows no evidence of being an AGN in optical, UV, and radio observations, suggesting the critical importance of high spatial resolution hard X-ray observations (>2 keV) in finding these binary AGNs. A high level of star formation combined with a very low L [O iii ] / L 2–10 keV ratio cause the AGN to be missed in optical observations. 12 CO observations of the (3–2) and (2–1) lines indicate large amounts of molecular gas in the system that could be driven toward the black holes during the violent galaxy collision and be key to fueling the binary AGN. Mrk 739E has a high Eddington ratio of 0.71 and a small black hole (log M BH = 7.05 ± 0.3) consistent with an efficiently accreting AGN. Other than NGC 6240, this stands as the nearest case of a binary AGN discovered to date.