出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We have recently detected an absorption line component in the spectrum of the microquasar SS
433. We believe this component originates from the mass donor star. The absorption line component
has radial velocities opposite that of the disk, and the strength of the lines relative to the
continuum varies as expected for a supergiant mass donor star in the system. The spectrum resembles
that of a mid-A supergiant star. Recent observations by other groups have led to conflicting
results about the nature of the absorption spectrum. Here we present results from new blue spectra
of SS 433 that were made at the orbital and precessional phases when the mass donor is best
seen in the foreground above the plane of the obscuring disk. The orbital phase variations of the
absorption line velocities and strengths are consistent with line formation in the photosphere of an
A-supergiant companion. We present new estimates of the masses of both stars: Mo = 12:53:3
M and Mx = 4:40:8 M .
