Tsukuba Uchu Forum

129th Uchu Forum

Cosmic Ray Particle Acceleration by the Jet of Microquasar SS433 Probed through Radio Observations

Haruka Sakemi

Kagoshima University

Abstract
Since its discovery in the 1970s, the microquasar SS433 has attracted much attention as one of the most active jet objects in our Galaxy and has been the subject of numerous studies. However, there are still many unresolved questions, such as the identity of the main star and companion star and the distance to the source. Furthermore, the origin of the giant radio nebula W50 surrounding SS433 is not fully understood. Recently, TeV gamma rays were detected from the SS433 jet. This indicates that cosmic rays are accelerated to high energies by the jet, suggesting that X-ray binary stars including microquasars are one of the dominant sources of cosmic ray acceleration in the system. Theoretical studies have claimed that cosmic rays can be accelerated to energies higher than $10^{15}$ eV by shock waves formed in the system's jets, and this is expected to be an important step toward understanding the identity of cosmic-ray acceleration sources in the long-unresolved energy range of $10^{15}\sim10^{18}$ eV. In this talk, I will introduce the basic properties and unsolved problems of SS433/W50, with a special focus on its properties as a cosmic-ray acceleration source, and the results of estimating the highest energy at which cosmic rays can be accelerated based on radio observations.