GeV {\gamma}-ray Emission Detected by Fermi-LAT Probably Associated with the Thermal Composite Supernova Remnant Kesteven 41 in a Molecular Environment

TL;DR

This paper reports the detection of GeV gamma-ray emission from the supernova remnant Kesteven 41, likely originating from hadronic interactions with a nearby molecular cloud, providing insights into cosmic-ray acceleration in SNRs.

Contribution

First detection of GeV gamma-ray emission associated with Kesteven 41, supporting hadronic origin and expanding understanding of SNR-molecular cloud interactions.

Findings

Gamma-ray emission with exponential cutoff spectrum detected at SNR location.

Emission consistent with hadronic interactions between shock-accelerated protons and molecular cloud.

No significant variability or associated radio pulsar found.

Abstract

Hadron emission from supernova remnant (SNR)-molecular cloud (MC) association systems has been widely regarded as a probe of the shock-accelerated cosmic-ray protons. Here, we report on the detection of a {\gamma}-ray emission source, with a significance of 24{\sigma} in 0.2-300 GeV, projected to lie to the northwest of the thermal composite SNR Kesteven 41, using 5.6 years of Fermi-Large Area Telescope (LAT) observation data. No significant long-term variability in the energy range 0.2--300 GeV is detected around this source. The 3{\sigma} error circle, 0.09 degree; in radius, covers the 1720MHz OH maser and is essentially consistent with the location of the V_{LSR} ~-50 km/s MC with which the SNR interacts. The source emission has an exponential cutoff power-law spectrum with a photon index of 1.9+/-0.1 and a cutoff energy of 4.0+/-0.9 GeV, and the corresponding 0.2-300 GeV luminosity is ~1.3*10^36 erg/s at a distance of 12 kpc. There is no radio pulsar in the 3{\sigma} circle responsible for the high {\gamma}-ray luminosity. While the inverse Compton scattering scenario would lead to a difficulty in the electron energy budget, the source emission can naturally be explained by the hadronic interaction between the relativistic protons accelerated by the shock of SNR Kesteven 41 and the adjacent northwestern MC. In this paper, we present a list of Galactic thermal composite SNRs detected at GeV {\gamma}-ray energies by Fermi-LAT is presented.