# Fermi LAT observation of VER J2019+407

## TL;DR

This paper reports the detection and analysis of gamma-ray emission from the supernova remnant G78.2+2.1 using Fermi LAT, identifying a likely counterpart to the TeV source VER J2019+407 with a broken power-law spectrum.

## Contribution

First detailed GeV gamma-ray analysis of VER J2019+407, establishing its connection to the supernova remnant G78.2+2.1 and characterizing its spectral properties.

## Key findings

- Detection of extended GeV emission coincident with VER J2019+407
- Spectrum smoothly connects with TeV observations, described by a broken power-law
- Multiple scenarios discussed for the source's nature

## Abstract

Analysis of data from the Fermi Large Area Telescope (LAT) in the region of the supernova remnant G78.2+2.1 reveals an excess at the position of the TeV source VER J2019+407. The GeV source is extended with a hard spectrum and it is likely the counterpart of the TeV source. The spectrum of the LAT emission connects smoothly with that of VER J2019+407, and the overall GeV--TeV spectrum is best described by a broken power-law with indices 1.8 and 2.5 below and above a break energy of 71 GeV. Several scenarios are considered to explain the nature of this unidentified gamma ray source.