Fast launch speeds in radio flares, from a new determination of the intrinsic motions of SS 433's jet bolides

TL;DR

This study uses high-resolution VLBA radio imaging to measure the intrinsic launch speeds of SS 433's jets during flares, revealing speeds up to 0.32c and providing a new method independent of optical spectroscopy.

Contribution

A novel radio-based method to determine jet launch speeds in SS 433, demonstrating rapid speed increases during flares and advancing understanding of jet dynamics.

Findings

Jet launch speeds reach up to 0.32c during flares

New radio method independent of optical spectroscopy

Flares are associated with increased jet speeds

Abstract

We present new high-resolution, multi-epoch, VLBA radio images of the Galactic microquasar SS 433. We are able to observe plasma knots in the milliarcsecond-scale jets more than 50 days after their launch. This unprecedented baseline in time allows us to determine the bulk launch speed of the radio-emitting plasma during a radio flare, using a new method which we present here, and which is completely independent of optical spectroscopy. We also apply this method to an earlier sequence of 39 short daily VLBA observations, which cover a period in which SS 433 moved from quiescence into a flare. In both datasets we find, for the first time at radio wavebands, clear evidence that the launch speeds of the milliarcsecond-scale jets rise as high as 0.32c during flaring episodes. By comparing these images of SS 433 with photometric radio monitoring from the RATAN telescope, we explore further properties of these radio flares.