The Struve-Sahade effect: A tale of three stars

The "Struve-Sahade effect" (S-S effect) is the apparent weakness of lines o f the secondary in massive binaries when the secondary is receding. This ef fect poses problems for the accurate reconstruction of the separated primar y and secondary spectra. We have reexamined IUE spectra of three classical, hot binaries studied by D. Stickland in 1997. From various cross-correlati on and tomographic techniques we find different results for each of the thr ee systems. For HD 1337 (AO Gas), we find a slight S-S effect which can be explained by a mechanism of localized heating by the colliding stellar wind s, as proposed by Gies, Bagnuolo, & Penny in 1997. For HD 47129 (Plaskett's star), no consistent S-S effect was found, and none is expected based on t he wind heating model because the secondary has a slightly stronger wind. F inally, for HD 57060 (29 UW CMa), a strong S-S effect was found during the receding phases (0113-0.63). In addition, we find a strong feature near pha se 0.2, similar to the secondary in spectral type but shifted by approximat e to -400 km s(-1). We explain this by absorption and reemission by strong winds wrapping around the secondary. Thus, in general, we find that the S-S effect may arise from several distinct mechanisms.