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Session 77 - Binary Stars.
Display session, Wednesday, January 15
Radiatively driven winds are found in all massive, luminous stars, and in close binary systems the individual winds will collide in a bow shock which will wrap around the star with the weaker wind. The geometrical and physical characteristics of the collision boundary and other dense regions in the wind depend on the individual wind density and velocity laws, plus the separation, orbital velocities, and evolutionary stage of the system. Given these variables, there will be a great diversity in colliding wind properties among observed binaries. Wind effects can be easily observed using optical spectroscopy, as high density regions in the wind (near the photospheres and the shock region) will produce H\alpha emission which can be used to map out the mass-flow structure of the system. We have completed a comprehensive all-sky survey of bright, massive binaries to search for observational evidence of colliding winds. Of the 32 systems studied, eight show dramatic emission which may be attributed to colliding winds. Three more systems show less dramatic, but still interesting excess emission. The strength of the emission appears to be correlated with the evolutionary stage of the system. We present here the visual spectroscopic data, as well as some preliminary analysis of the geometry of the systems.
Program listing for Wednesday