Energy estimation of high energy particles associated with the SS433/W50 system through radio observation at 1.4 GHz

TL;DR

This study uses radio and gamma-ray observations of the W50 nebula associated with SS433 to estimate the maximum energy and total energy of cosmic-ray protons accelerated by the system's jets.

Contribution

It provides new estimates of cosmic-ray proton energies and analyzes the stability and structure of W50 over 33 years using multi-epoch radio data.

Findings

Maximum energy of cosmic-ray protons exceeds 10^15.5 eV.

W50 structures remained stable over 33 years.

Estimated total energy of accelerated protons is below 5.2 x 10^48 erg.

Abstract

The radio nebula W50 is a unique object interacting with the jets of the microquasar SS433. The SS433/W50 system is a good target for investigating the energy of cosmic-ray particles accelerated by galactic jets. We report observations of radio nebula W50 conducted with the NSF's Karl G. Jansky Very Large Array (VLA) in the L band (1.0 -- 2.0 GHz). We investigate the secular change of W50 on the basis of the observations in 1984, 1996, and 2017, and find that most of its structures were stable for 33 years. We revise the upper limit velocity of the eastern terminal filament by half to 0.023$c$ assuming a distance of 5.5 kpc. We also analyze the observational data of the Arecibo Observatory 305-m telescope and identify the HI cavity around W50 in the velocity range 33.77 km s$^{-1}$ -- 55.85 km s$^{-1}$. From this result, we estimate the maximum energy of the cosmic-ray protons accelerated by the jet terminal region to be above 10$^{15.5}$ eV. We also use the luminosity of the gamma-rays in the range 0.5 -- 10 GeV to estimate the total energy of accelerated protons below 5.2 $\times$ 10$^{48}$ erg.