# Dual black hole associated with obscured and unobscured AGN: CXO J101527.2+625911

## TL;DR

This study investigates whether the offset AGN in CXO J101527.2+625911 is a recoiled supermassive black hole or a dual black hole system, using high-resolution radio and optical observations.

## Contribution

The paper provides multi-wavelength high-resolution evidence supporting the presence of a dual black hole system instead of a recoiled SMBH in the galaxy.

## Key findings

- Detected a single compact radio source at the galaxy center.
- High brightness temperature indicates AGN activity.
- Optical spectra show two narrow emission line components.

## Abstract

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 had suggested that the offset AGN, which has an angular separation of only 0\farcs26 from the center of the host galaxy, is a recoiled Super Massive Black Hole (rSMBH). We carried out high angular resolution observations with both the VLBA (1.54 GHz) and the VLA (10.0 GHz \& 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 $T_b=7.2\times10^{7}$ 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\AA 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 a rSMBH.