# Discovery of the TeV Emission from the JetInteraction Regions of SS 433 with HAWC

## TL;DR

This paper reports the discovery of TeV gamma-ray emission from the jet interaction regions of SS 433 using HAWC, providing evidence for in-situ particle acceleration at energies above a few TeV.

## Contribution

It presents new HAWC observations confirming TeV emission from SS 433's jet regions, supporting leptonic processes over hadronic models.

## Key findings

- Detection of multi-TeV gamma rays from SS 433's jet regions.
- Evidence favoring leptonic over hadronic gamma-ray production.
- Confirmation of in-situ particle acceleration at TeV energies.

## Abstract

The High Altitude Water Cherenkov (HAWC) observatory recently published the discovery of SS 433 as a TeV source, reporting the observation of multi-TeV gamma-ray emission from the jet interaction regions e1 and w1, suggesting in-situ particle acceleration. This showed the first direct evidence of acceleration in jets at energies greater than a few TeV. SS 433 was the first microquasar to be discovered and is still considered special in that the accretion is supercritical and the luminosity of the system is very high ($\sim10^{40}$ erg s$^{-2}$). The lobes of the supernova remnant W 50 in which the jets terminate, about 40 parsecs from the central binary, are expected to accelerate charged particles, and indeed radio and X-ray emission consistent with electron synchrotron emission in a magnetic field have been observed. SS 433 has also been a strong candidate for hadronic acceleration due to spectroscopic evidence of ionized nuclei in the inner jets. However, multiwavelength fits including the HAWC measurements favor the leptonic production of the observed gamma rays. Here, we present new follow-up measurements of the jet interaction regions of SS 433 using the most recent data from HAWC.