A pair of UV nuclei or a compact star forming region near the active nucleus in Mrk~766?

TL;DR

A bright, compact UV source near the AGN in Mrk 766 was discovered, likely representing a star-forming region rather than a second black hole, based on multi-wavelength analysis.

Contribution

This study reports the first detection of a UV source near Mrk 766's nucleus, identifying it as a star-forming region through flux analysis and multi-wavelength comparison.

Findings

The UV source is unlikely to be an accreting black hole due to lack of X-ray emission.

The UV/optical flux matches starburst galaxy spectra.

The source is separated by 1.1 kpc from the AGN.

Abstract

We report the discovery of a bright, compact ultraviolet source at a projected separation of 1.1~kpc from the known active galactic nucleus (AGN) in Mrk~766 based on Astrosat/UVIT observations. We perform radial profile analysis and derive the UV flux almost free from the nearby contaminating sources. The new source is about 2.5 and 5.6 times fainter than the AGN in the far and near UV bands. The two sources appear as a pair of nuclei in Mrk~766. We investigate the nature of the new source based on the UV flux ratio, X-ray and optical emission. The new source is highly unlikely to be another accreting supermassive black hole in Mrk~766 as it lacks X-ray emission. We find that the UV/Optical flux of the new source measured at four different bands closely follow the shape of the template spectrum of starburst galaxies. This strongly suggests that the new source is a compact star-forming region.