Discovery of gamma-ray emission from a strongly lobe-dominated quasar 3C 275.1

TL;DR

This study reports the discovery of gamma-ray emission from the lobe-dominated quasar 3C 275.1 using 6 years of Fermi/LAT data, highlighting its significance among similar quasars and exploring possible emission models.

Contribution

First detection of gamma-ray emission from 3C 275.1, a lobe-dominated quasar with low core dominance, and analysis of emission models favoring the parsec jet scenario.

Findings

Gamma-ray emission detected from 3C 275.1.

Significant variability observed in 3C 207.

Potential contribution of LDQs to the extragalactic gamma-ray background.

Abstract

We systematically analyze the 6-year {\it Fermi}/LAT data of the lobe-dominated quasars (LDQs) in the complete LDQ sample from 3CRR survey and report the discovery of high-energy $\gamma$-ray emission from 3C 275.1. The $\gamma$-ray emission of 3C 207 is confirmed and significant variability of the lightcurve is identified. We do not find statistically significant $\gamma$-ray emission from other LDQs. 3C 275.1 is the known $\gamma$-ray quasar with the lowest core dominance parameter (i.e., $R=0.11$). We also show that both the northern radio hotspot and parsec jet models can reasonably reproduce the $\gamma$-ray data. The parsec jet model, however, is favored by the potential $\gamma$-ray variability at the timescale of months. We suggest that some dimmer $\gamma$-ray LDQs will be detected in the future and LDQs could contribute non-negligibly to the extragalactic $\gamma$-ray background.