Modeling the multiwavelength emission from G73.9+0.9: Gamma-rays from a SNR-MC interaction

TL;DR

This paper models the broadband non-thermal emission of G73.9+0.9, a supernova remnant possibly interacting with molecular clouds, using 7 years of Fermi-LAT gamma-ray data, and suggests a hadronic origin for the high-energy emission.

Contribution

It provides a comprehensive broadband model including new gamma-ray observations and evaluates the emission mechanisms, favoring a hadronic origin over leptonic or PWN scenarios.

Findings

Gamma-ray detection with 13-sigma significance above 200 MeV.

Gamma-ray spectrum best described by a power law with index -2.5.

Hadronic processes are the most plausible explanation for the emission.

Abstract

G73.9+0.9 has been classified as a probable shell-type supernova remnant (SNR), although it has also been suggested that this object could be a pulsar wind nebula (PWN). Here, a broadband model of the non-thermal emission of G73.9+0.9 from radio to gamma-rays is presented. The model includes a new gamma-ray observation obtained with analysis of 7 years of data from the Fermi-LAT telescope. Above 200 MeV the source is detected with a significance of 13-sigma and the spectrum of the radiation is best described by a power law with an index of -2.5. The leptonic mechanisms are hard to reconcile with the measured radio and gamma-ray SED. A PWN origin for the high-energy emission is also not very likely, due to the lack of detection of pulsars and of X-ray emission in the region, as well as from the shape of the gamma-ray spectrum. Given the possibility that the object is interacting with molecular clouds, a hadronic origin of the high-energy emission is more likely, and the spectral properties of the cosmic rays responsible for this radiation are derived.