SS 433: The accretion disk revealed in H alpha

TL;DR

This study provides spectroscopic evidence of an accretion disk in SS 433, revealing its dynamics, mass estimates, and the behavior of the system during a flare, confirming the presence of a super-Eddington accretor.

Contribution

First direct spectroscopic detection of the accretion disk in SS 433, with detailed velocity measurements and mass constraints of the system components.

Findings

Accretion disk material orbits at >500 km/s.

Mass of the compact object is less than 37 solar masses.

The companion star's mass is between 20 and 30 solar masses.

Abstract

{The Galactic microquasar SS 433 is very luminous and ejects opposite jets at approximately one quarter the speed of light. It is regarded as a super-Eddington accretor but until recently there were no observations of accretion.} % aims heading (mandatory) {To present an analysis of spectroscopic optical data obtained before and during a major flare, which yield in H$\alpha$ unambiguous evidence for the accretion disk.} % methods heading (mandatory) {Published high resolution spectra, taken with a 3.6-m telescope almost nightly over 0.4 of a precession cycle, are analysed.} % results heading (mandatory) {Optical spectra taken almost nightly in August and September 2004 revealed a period of quiescence followed by activity which culminated in the accretion disk of SS433 becoming visible. The visible material in the accretion disk orbited the compact object at greater than 500 km s$^{-1}$, implying that the mass of the compact object is less than 37 $M_\odot$. Evidence that an accretion stream joins the disk at over 700 km s$^{-1}$ suggests that the mass is considerably below this upper limit. The accretion disk clearly orbits the centre of mass of the binary system with the compact object, sharing its speed of approximately 175 km s$^{-1}$. The mass of the companion lies between 20 and 30 $M_\odot$ and it probably does not fill its Roche lobe.}