Gamma-ray variability of radio-loud narrow-line Seyfert 1 galaxies

TL;DR

This study analyzes gamma-ray light curves of four radio-loud narrow-line Seyfert 1 galaxies, revealing significant variability that confirms the presence of relativistic jets similar to blazars, and estimates their emission region sizes.

Contribution

It provides the first detailed variability analysis of gamma-ray emission in radio-loud narrow-line Seyfert 1 galaxies, confirming jet activity and estimating emission region sizes.

Findings

Detected significant gamma-ray flux variability in all sources

Excluded starburst origin for gamma-ray emission

Estimated emission region sizes between 0.2 and 2 parsecs

Abstract

The recent detection of gamma-ray emission from four radio-loud narrow-line Seyfert 1 galaxies suggests that the engine driving the AGN activity of these objects share some similarities with that of blazars, namely the presence of a gamma-ray emitting, variable, jet of plasma closely aligned to the line of sight. In this work we analyze the gamma-ray light curves of the four radio-loud narrow-line Seyfert 1 galaxies for which high-energy gamma-ray emission has been discovered by Fermi/LAT, in order to study their variability. We find significant flux variability in all the sources. This allows us to exclude a starburst origin of the gamma-ray photons and confirms the presence of a relativistic jet. Furthermore we estimate the minimum e-folding variability timescale (3 - 30 days) and infer an upper limit for the size of the emitting region (0.2 - 2 pc, assuming a relativistic Doppler factor delta=10 and a jet aperture of theta=0.1 rad).