Deciphering the Origin of the GeV--TeV Gamma-ray Emission from SS 433

TL;DR

This study explores hadronic and leptonic models for the GeV--TeV gamma-ray emission from SS 433's jets, finding both can explain observations and future telescopes may distinguish the mechanisms.

Contribution

It presents detailed modeling of gamma-ray emission mechanisms in SS 433, highlighting the potential to differentiate hadronic and leptonic scenarios with upcoming observations.

Findings

Both models fit current data including Fermi LAT results.

Hadronic models predict higher-energy photons than leptonic models.

Future observations could identify the dominant emission mechanism.

Abstract

We investigate hadronic and leptonic scenarios for the GeV--TeV gamma-ray emission from jets of the microquasar SS 433. The emission region of the TeV photons coincides with the X-ray knots, where electrons are efficiently accelerated. On the other hand, the optical high-density filaments are also located close to the X-ray knots, which may support a hadronic scenario. We calculate multi-wavelength photon spectra of the extended jet region by solving the transport equations for the electrons and protons. We find that both hadronic and leptonic models can account for the observational data, including the latest {\it Fermi} LAT result. The hadronic scenarios predict higher-energy photons than the leptonic scenarios, and future observations such as with the Cherenkov Telescope Array (CTA), the Large High-Altitude Air Shower Observatory (LHAASO), and the Southern Wide-field Gamma-ray Observatory (SWGO) may distinguish between these scenarios and unravel the emission mechanism of GeV--TeV gamma-rays. Based on our hadronic scenario, the analogy between microquasars and radio galaxies implies that the X-ray knot region of the radio-galaxy jets may accelerate heavy nuclei up to ultrahigh energies.