Gamma-ray heartbeat powered by the microquasar SS 433

TL;DR

This study analyzes over ten years of Fermi gamma-ray data on SS 433, revealing emission linked to gas enhancements and jet lobes, with periodic variation matching the precessional period, challenging existing models.

Contribution

It provides the first detailed analysis of long-term gamma-ray data on SS 433, uncovering emission features and periodicity that challenge current theoretical understanding.

Findings

Gamma-ray emission is associated with gas enhancements near SS 433.

Emission shows periodic variation at the precessional period.

Results challenge existing models of microquasar gamma-ray emission.

Abstract

Microquasars, the local siblings of extragalactic quasars, are binary systems comprising a compact object and a companion star. By accreting matter from their companions, microquasars launch powerful winds and jets, influencing the interstellar environment around them. Steady gamma-ray emission is expected to rise from their central objects, or from interactions between their outflows and the surrounding medium. The latter prediction was recently confirmed with the detection of SS 433 at high (TeV) energies. In this report, we analyze more than ten years of GeV gamma-ray data from the Fermi Gamma-ray Space Telescope on this source. Detailed scrutiny of the data reveal emission in the SS 433 vicinity, co-spatial with a gas enhancement, and hints for emission possibly associated with a terminal lobe of one of the jets. Both gamma-ray excesses are relatively far from the central binary, and the former shows evidence for a periodic variation at the precessional period of SS 433, linking it with the microquasar. This result challenges obvious interpretations and is unexpected from any previously published theoretical models. It provides us with a chance to unveil the particle transport from SS 433 and to probe the structure of the local magnetic field in its vicinity.