# AGILE study of the gamma-ray emission from the SNR G78.2+2.1 (Gamma Cygni)

## TL;DR

This study analyzes gamma-ray emission from SNR G78.2+2.1 using AGILE data, revealing that off-pulse emission overlaps the radio shell and can be explained by a lepton-dominated model involving Bremsstrahlung and inverse Compton processes.

## Contribution

It provides the first detailed analysis of gamma-ray emission from SNR G78.2+2.1 during pulsar off-pulse phases, proposing a lepton-dominated emission scenario.

## Key findings

- Off-pulse gamma-ray emission overlaps the radio shell boundary.
- A lepton-dominated double population model explains the gamma-ray and radio emission.
- Different processes dominate at different energy ranges, with Bremsstrahlung and inverse Compton contributions.

## Abstract

We present a study on the gamma-ray emission detected by the AGILE-GRID from the region of the SNR G78.2+2.1 (Gamma Cygni). In order to investigate the possible presence of gamma rays associated with the SNR below 1 GeV, it is necessary to analyze the gamma-ray radiation underlying the strong emission from the pulsar PSR J2021+4026, which totally dominates the field. An "off-pulse" analysis has been carried out, by considering only the emission related to the pulsar off-pulse phase of the AGILE-GRID light curve. We found that the resulting off-pulsed emission in the region of the SNR - detected by the AGILE-GRID above 400 MeV - partially overlaps the radio shell boundary. By analyzing the averaged emission on the whole angular extent of the SNR, we found that a lepton-dominated double population scenario can account for the radio and gamma-ray emission from the source. In particular, the MeV-GeV averaged emission can be explained mostly by Bremsstrahlung processes in a high density medium, whereas the GeV-TeV radiation by both Bremsstrahlung (E < 250 GeV) and inverse Compton processes (E > 250 GeV) in a lower density medium.