Chandra Discovery of a Candidate Hyperluminous X-Ray Source in MCG+11-11-032

Abstract

We present a multiwavelength analysis of MCG+11-11-032, a nearby active galactic nucleus (AGN), with a unique classification as being both a binary and a dual AGN candidate. With new Chandra observations, we aim to resolve any dual AGN system via imaging data and search for signs of a binary AGN via analysis of the X-ray spectrum. Analyzing the Chandra spectrum, we find no evidence of the previously suggested double-peaked Fe K α lines; the spectrum is instead best fit by an absorbed power law with a single Fe K α line, as well as an additional line centered at ≈7.5 keV. The Chandra observation reveals faint, soft, and extended X-ray emission, possibly linked to low-level nuclear outflows. Further analysis shows evidence for a compact hard source—MCG+11-11-032 X2—located 3 $\mathop{.}\limits^{\unicode{x02033}}$ 3 from the primary AGN. Modeling MCG+11-11-032 X2 as a compact source, we find that it is relatively luminous ( ${L}_{\,\rm{2\unicode{x02013}10 keV}\,}=1.{5}_{-0.5}^{+0.9}\times 1{0}^{41}$ erg s ^−1 ), and the location is coincident with a compact and off-nuclear source resolved in Hubble Space Telescope infrared (F105W) and optical (F621M, F547M) bands. Pairing our X-ray results with a 144 MHz radio detection at the host galaxy location, we observe X-ray and radio properties similar to those of ESO 243-49 HLX-1, suggesting that MCG+11-11-032 X2 may be a hyperluminous X-ray source. This detection with Chandra highlights the importance of a high-resolution X-ray imager as well as how previous binary AGN candidates detected with large-aperture instruments can benefit from high-resolution follow-up. Future spatially resolved optical spectra, and deeper X-ray observations, can better constrain the origin of MCG+11-11-032 X2.

Keywords

• X-ray active galactic nuclei
• Galaxy mergers
• Supermassive black holes
• Intermediate-mass black holes