Possible evidence for disk emission in SS 433

Optical and N/R spectra of SS 433 having moderate resolution (2-4 A) and exceptionally high signal-to-noise ratios (100/1 to 200/1), obtained a few days prior to the crossover time of the moving-line systems are presented. The strong Paschen lines of the stationary (rest wavelength) system exhibit a remarkable double-peaked structure (Delta v about 290 km/s), suggestive of emission from a rotating disklike region. Several unblended Fe II lines also consist of double peaks centered on the systemic velocity. Both the Paschen and the Balmer stationary-line profiles show substantial variation over the three nights spanning the observations. Interesting changes are also seen in the moving-line system; in particular, emission is detected from several members of the Paschen series. If the proposed identification of the disk emission is confirmed, detailed observations would probe the accretion disk structure and provide estimates of the mass of each component in the system.