2019ApJ...882..149K

We report the results of an investigation to determine the nature of the offset active galactic nucleus (AGN) found in the source CXO J101527.2+625911. Hubble Space Telescope and Chandra X-ray observatory data have suggested that the offset AGN, which has an angular separation of only 0.''26 from the center of the host galaxy, is a recoiled supermassive black hole (rSMBH). We carried out high angular resolution observations with both the Very Long Baseline Array (1.54 GHz) and the Very Large Array (10.0 GHz and 33.0 GHz) and detected a single compact radio source in the center of the host galaxy, with no radio continuum emission associated with the offset AGN. The detected radio source has a high brightness temperature value of T_b = 7.2 x 10⁷ K, indicating that the radio emission is associated with an AGN. Furthermore, we present the decomposition of high-resolution KECK spectra of the [O III] 5007 Å line into two narrow emission line components, which is a characteristic sign of a dual black hole system. These new radio and optical wavelength results suggest that CXO J101527.2+625911 is the host of a dual black hole system rather than an rSMBH.