Gamma-ray echoes from SS 433

TL;DR

This paper reports the detection of gamma-ray sources associated with SS 433, including a variable source with periodicity, and discusses a proposed scenario involving relativistic protons illuminating distant gas clouds, highlighting energetic constraints.

Contribution

It presents the first detection of gamma-ray echoes from SS 433 and proposes a novel scenario for their origin involving relativistic protons and dense gas clouds.

Findings

Detection of gamma-ray sources near SS 433.

Identification of a variable gamma-ray component with 160-day periodicity.

Energetic constraints challenge the proposed emission scenario.

Abstract

The detection of two sources of gamma rays towards the microquasar SS 433 has been recently reported. The first source can be associated with SS 433's eastern jet lobe, whereas the second source is variable and displays significant periodicity compatible with the precession period of the binary system, of about 160 days. The location of this variable component is not compatible with the location of SS 433 jets. To explain the observed phenomenology, a scenario based on the illumination of dense gas clouds by relativistic protons accelerated at the interface of the accretion disk envelope has been proposed. Energetic arguments strongly constrain this scenario, however, as it requires an unknown mechanism capable to periodically channel a large fraction of SS 433's kinetic energy towards an emitter located 36 parsec away from the central binary system.