Detection of persistent gamma-ray emission toward SS433/W50

TL;DR

This paper reports the first detection of persistent gamma-ray emission from the SS433/W50 microquasar system, indicating proton-proton collisions at jet interaction regions as the source, with implications for galactic cosmic-ray contributions.

Contribution

It provides the first observational evidence of steady gamma-ray emission from SS433/W50, linking jet kinetic power to gamma-ray production via proton-proton collisions.

Findings

Detected steady gamma-ray emission with Fermi LAT.

Gamma-ray spectrum peaks around 250 MeV.

Implication for microquasar jets contributing to galactic cosmic rays.

Abstract

The microquasar SS433 features the most energetic jets known in our Galaxy. A large fraction of the jet kinetic power is delivered to the surrounding W50 nebula at the jet termination shock, from which high-energy emission and cosmic-ray production have been anticipated. Here we report on the detection of a persistent gamma-ray signal from the direction of SS433/W50 with the Fermi Large Area Telescope. The steady flux and a narrow spectral energy distribution with a maximum around 250 MeV suggest that gamma-rays are rendered by the bulk jet kinetic power through proton-proton collisions at the SS433/W50 interaction regions. If the same mechanism is operating in other baryon-loaded microquasar jets, their collective contribution may represent a significant fraction of the total galactic cosmic-ray flux at GeV energies.