SS433—a massive black hole?

Abstract

SPECTROPHOTOMETRIC observations by Margon et al.¹ have drawn attention to some remarkable spectroscopic activity in the object Stephenson–Sanduleak 433. In addition to broad, intense Balmer, He I and He II emission lines, Margon et al.¹ report the presence of broad, strong anomalous emission lines which move rapidly across the spectrum. For example, their Fig. 3 shows the behaviour of two such lines (one at ∼6,000 Å and the other at ∼7,400 Å with mean value just redwards of Hα) on three nights in a four-day interval. The IR line moved redwards by ∼150 Å and the red line bluewards by ∼70 Å. If interpreted as Doppler shifts these movements imply velocity changes of 6,000 km s⁻¹ and −3,500 km s⁻¹ respectively. We propose here that these anomalous emission lines are produced by an emitting ring of gas in a circular orbit around a central, massive black hole.