# Fermi-LAT Observations of Extreme Spectral Variability in IC 310

## TL;DR

This study analyzes eight years of Fermi-LAT data to reveal extreme spectral variability in the gamma-ray emission of IC 310, including new soft states and low-energy detections, highlighting complex emission mechanisms.

## Contribution

It provides the first detection of IC 310 below 1 GeV and uncovers significant spectral state changes, advancing understanding of gamma-ray variability in misaligned AGNs.

## Key findings

- Detection of IC 310 below 1 GeV for the first time
- Identification of a previously unknown soft spectral state
- Observation of a shift in peak Compton energy by over five orders of magnitude

## Abstract

We investigate the physical mechanisms of high-energy gamma-ray emission from the TeV-emitting misaligned active galactic nucleus IC 310. Eight years of data from the Fermi Large Area Telescope (Fermi-LAT) between 100 MeV and 500 GeV are reduced and analysed to study the temporal and spectral characteristics of IC 310. Point spread function-partitioned instrument response functions are used to improve the resolvability of IC 310 from nearby NGC 1275. Systematic effects due to this choice of instrument response functions and the proximity of NGC 1275 are investigated. We find strong spectral variability and detect the hard flaring state of IC 310 along with a previously undiscovered soft state in quiescent periods, and the first detection with Fermi-LAT below 1 GeV. This represents a shift in peak Compton energy of more than five orders of magnitude. Possible interpretations are discussed, but we lack the instantaneous sensitivity with Fermi to probe the underlying physics.