Properties of the ζ Aur-Type Binary System 22 Vul = QS Vul

The 22 Vul system is important for studying the winds and chromospheres of cool evolved stars because the G4 I component is rotating rapidly and probably faster than synchronously. We discuss the system's physical properties in the context of a wide range of constraints on them and propose values that may be marginally better than previous ones (see the end of § 3). We use Hα spectroscopy to assess the variability of the cool star's wind, and archival IUE observations to measure variation of density in the wind and rotation of the chromosphere. We argue that the terminal velocity of the wind must be at least as great as the edge velocity of Mg II and derive a new value of v ∞ ≳ 208 ± 5 km s -1 . Directly measured column densities for hydrogen (from Lyα), combined with column densities for metals, imply a β ∼ 2.5 velocity law for the wind with a mass-loss rate of ∼1.6 × 10 -8 M ⊙ yr -1 , about 4 times the surface flux of 31 Cyg. Excitation temperatures and turbulent velocities in the inner 3 R * of the wind are similar to those in other ζ Aur binaries. The apparent faster-than-synchronous rotation Griffin and coworkers found in the optical persists in IUE spectra out to at least 2.5 R (G4 I). This implies that the wind is locked to the star through magnetic fields or that the material in the wind is viscous enough to maintain approximately solid-body rotation.