NuSTAR Resolves the First Dual AGN above 10 keV in SWIFT J2028.5+2543
Abstract
We have discovered heavy obscuration in the dual active galactic nucleus (AGN) in the Swift/Burst Alert Telescope (BAT) source SWIFT J2028.5+2543 using Nuclear Spectroscopic Telescope Array (NuSTAR). While an early XMM-Newton study suggested the emission was mainly from NGC 6921, the superior spatial resolution of NuSTAR above 10 keV resolves the Swift/BAT emission into two sources associated with the nearby galaxies MCG +04-48-002 and NGC 6921 (z = 0.014) with a projected separation of 25.3 kpc (91″). NuSTAR's sensitivity above 10 keV finds both are heavily obscured to Compton-thick levels (N H ≈ (1-2) × 1024 cm-2) and contribute equally to the BAT detection ({L}10-50 {keV}{{int}} ≈ 6 × 1042 erg s-1). The observed luminosity of both sources is severely diminished in the 2-10 keV band ({L} 2-10 {keV}{{obs}}\lt 0.1× {L} 2-10 {keV}{{int}}), illustrating the importance of >10 keV surveys like those with NuSTAR and Swift/BAT. Compared to archival X-ray data, MCG +04-48-002 shows significant variability (>3) between observations. Despite being bright X-ray AGNs, they are difficult to detect using optical emission-line diagnostics because MCG +04-48-002 is identified as a starburst/composite because of the high rates of star formation from a luminous infrared galaxy while NGC 6921 is only classified as a LINER using line detection limits. SWIFT J2028.5+2543 is the first dual AGN resolved above 10 keV and is the second most heavily obscured dual AGN discovered to date in the X-rays other than NGC 6240.
- Publication:
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The Astrophysical Journal
- Pub Date:
- June 2016
- DOI:
- 10.3847/2041-8205/824/1/L4
- arXiv:
- arXiv:1708.06762
- Bibcode:
- 2016ApJ...824L...4K
- Keywords:
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- galaxies: active;
- galaxies: individual: NGC 6921;
- MCG +04-48-002;
- galaxies: interactions;
- X-rays: galaxies;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- Published in ApJ, 7 pages, 4 figures