Michael S. Wiggs

We present high-quality Hα spectra of the massive X-ray binary HDE 226868 = Cyg X-1 that were made in 1985 and 1986. We measured radial velocities using the He I λ6678 line, and we use the resulting orbital solution together with a Hipparcos light curve of the ellipsoidal variation to arrive at a revised period estimate of P = 5.59977 ± 0.00002 days. We analyze the orbital phase-related variations in Hα emission using a Doppler tomography algorithm, and we show that the profile variations are well matched by a linear combination of two components: a P Cygni profile that moves with the motion of the supergiant star and an emission component that follows an antiphase but phase-shifted velocity curve (semiamplitude K_em = 68 km s^-1 and radial velocity maximum at ₀ = 0.86; these parameters are similar to those for the He II λ4686 emission line). We use a vector decomposition of this motion to argue that the latter emission component forms between the stars in a focused wind flow from the supergiant to the unseen companion. We searched for but found no clear evidence of Hα emission from the accretion disk surrounding the companion (any such emission contributes less than 3% of the continuum intensity). The results demonstrate that the Hα line provides an important probe of the mass transfer process that eventually fuels the X-ray source.

We present high-quality spectra of the Hα emission line of the nova-like variable V Sge, obtained during a photometric bright state during 1986 July. The profiles have several components, including (1) a very broad, flat-topped emission line that forms in the optically thin wind of one of the stars, (2) a central, narrow peak that probably originates in a circumbinary shell, and (3) a moving component that attains an extreme velocity of approach just prior to secondary eclipse (when the brighter and lower mass Roche lobe–filling primary star is in the foreground). We review models for the emission based on the expected collision of the stellar winds of both stars, and suggest that the moving component originates in a high-density region that extends from between the stars to above the leading hemisphere of the primary. The example of V Sge shows that interacting binaries may cease mass transfer in favor of mass ejection from the system at some stage in their evolution.