SS433: Observation of the circumbinary disc and extraction of the system mass

TL;DR

This study analyzes SS433's H-alpha spectral lines, revealing a circumbinary ring and estimating the system's total mass and the nature of its compact object as a massive stellar black hole.

Contribution

It provides the first detailed observation of a circumbinary disc in SS433 and estimates the system's mass, supporting the black hole hypothesis.

Findings

Identification of a circumbinary ring emitting narrow spectral components

Estimated system mass around 40 solar masses

Compact object likely a massive stellar black hole

Abstract

The so-called "stationary" H-alpha line of SS433 is shown to consist of three components. A broad component is identified as emitted in that wind from the accretion disc which grows in speed with elevation above the plane of the disc. There are two narrow components, one permanently redshifted and the other permanently to the blue. These are remarkably steady in wavelength and must be emitted from a circumbinary ring, orbiting the centre of mass of the system rather than orbiting either the compact object or its companion: perhaps the inner rim of an excretion disc. The orbiting speed (approximately 200 km/s) of this ring material strongly favours a large mass for the enclosed system (around 40 solar masses), a large mass ratio for SS433, a mass for the compact object plus accretion disc of ~16 solar masses and hence the identity of the compact object as a rather massive stellar black hole.