Supernova Remnant Kesteven 27: Interaction with A Neighbor HI Cloud Viewed by Fermi

TL;DR

This paper reports the likely detection of gamma-ray emission from supernova remnant Kes 27, associated with its interaction with a nearby HI cloud, analyzed using 5.7 years of Fermi LAT data, supporting a hadronic emission model.

Contribution

First detection of gamma-ray emission from Kes 27 linked to its interaction with a neighboring HI cloud, analyzed with extensive Fermi LAT data and modeled with a hadronic scenario.

Findings

Gamma-ray emission detected at Kes 27's position.

Emission spectrum fits a power-law with photon index 2.5.

Emission consistent with hadronic interaction of protons with dense cloud.

Abstract

We report on the likely detection of gamma-ray emission from the supernova remnant (SNR) Kesteven 27 (Kes 27). We analyze 5.7 yr Fermi Large Area Telescope data of the SNR region and find an unresolved source at a position consistent with the radio brightness peak and the X-ray knot of Kes 27, which is located in the eastern region of the SNR and caused by the interaction with a nearby HI cloud. The source's emission is best fit with a power-law spectrum with a photon index of 2.5 +/- 0.1 and a >0.2 GeV luminosity of 5.8*10^34 erg s^-1 assuming a distance of 4.3 kpc, as derived from radio observations of the nearby HI cloud. Comparing the properties of the source with that of other SNRs that are known to be interacting with nearby high-density clouds, we discuss the origin of the source's emission. The spectral energy distribution of the source can be described by a hadronic model that considers the interaction of energetic protons, escaping from the shock front of Kes 27, with a high-density cloud.