SS 433 Optical Flares: A New Analysis Reveals Their Origin in L2 Overflow Episodes

Abstract

The microquasar SS 433 exhibits in Hα intermittent flares. A sequence of observations made in 2004 showed flaring Doppler shifted to both the red and the blue simultaneously. The mean shifts varied from day to day, following the orbital phase of the compact object. At the time, this behaviour was interpreted as indicating an origin in the outer rim of the accretion disk. A new analysis of these old data, presented in this paper, shows that the flares are not eclipsed by the Companion that eclipses the photosphere surrounding the compact object. They are therefore not intermittent sightings of an accretion disk. The alternative explanation is plasma expelled through the L2 point, following the phase of the orbit as it invades the space beyond the system. That space has been mapped with comparatively recent GRAVITY observations of a similar flare in Brγ, indeed revealing a strong rotation component.

SS 433: Flares and L2 Overflow, Spirals in the Wind

“…This stimulated me to investigate whether it would be possible to distinguish H𝛼𝛼 spectra from an accretion disk or, rather, from material in the outer regions of the system. To my considerable surprise I obtained an unambiguous result [7], in that those flare spectra did not experience any eclipse by the Companion and so could not be a series of views of the accretion disk. This raised the question of how could it be that the trajectories exhibited a Doppler shift of ~ 350 𝑘𝑘𝑘𝑘 𝑠𝑠 −1 between extremes, over half the orbital period of the binary?…”

“…The most relevant representation of these deceptive data is provided in Figure 1; originally shown in [6] (and again in [7]). The red and blue flare components were fitted to gaussian distributions and the Doppler shifts of the mid points plotted, day by day, as a function of the phase of the binary system.…”

“…The Doppler shifts of the blue and red flare components as orbital phase advances (from [6,7]). The superimposed curves assumed the source to be the accretion disk, hence the distinct memory of orbital phase.…”

“…The difference in recessional speeds is responsible for the perceived difference in Doppler shift between phase 0.75 and on to 0.25. This is as far as the analysis went in [7], which was primarily concerned with the evidence that the flare spectra were not visions of the accretion disk, but formed in the wider environment. This paper takes up the investigation at that point.…”

“…The general appearance is what might be expected from a ring rotating with this speed and looked at almost edge on. The data were originally interpreted as from the accretion disk [4,6] and this interpretation proved to be completely wrong [7].…”