Identifying Three New AGNs Among Fermi Unidentified Gigaelectronvolt Sources

TL;DR

This study successfully identified three previously unknown Fermi gamma-ray sources as active galactic nuclei, specifically blazars, through multi-wavelength observations and analysis of their variability, optical counterparts, and spectral energy distributions.

Contribution

The paper presents the first identification of three Fermi unassociated gamma-ray sources as AGNs using multi-wavelength data and variability analysis, expanding the catalog of known gamma-ray blazars.

Findings

All three sources show gamma-ray flux variability.

Optical counterparts with similar variability patterns were identified.

Broadband spectral energy distributions support their classification as blazars.

Abstract

We report our identification of three gigaelectronvolt $\gamma$-ray sources, 4FGL J0502.6+0036, 4FGL J1055.9+6507, and 4FGL J1708.2+5519, as Active Galactic Nuclei (AGNs). They are listed in the latest Fermi-LAT source catalog as unidentified ones. We find that the sources all showed $\gamma$-ray flux variations in recent years. Using different survey catalogs, we are able to find a radio source within the error circle of each source's position. Further analysis of optical sources in the fields allows us to determine the optical counterparts, which showed similar variation patterns to those seen in $\gamma$-rays. The optical counterparts have reported redshifts of 0.6, 1.5, and 2.3, respectively, estimated from photometric measurements. In addition, we also obtain an X-ray spectrum of 4FGL J0502.6+0036 and a flux upper limit on the X-ray emission of 4FGL J1055.9+6507 by analyzing the archival data. The broadband spectral energy distributions of the three sources from radio to $\gamma$-rays are constructed. Comparing mainly the $\gamma$-ray properties of the three sources with those of different sub-classes of AGNs, we tentatively identify them as blazars. Followup optical spectroscopy is highly warranted for obtaining their spectral features and thus verifying the identification.