ON THE NATURE OF THE AM PHENOMENON OR ON A STABILIZATION AND THE TIDAL MIXING IN BINARIES .2. METALLICITY AND PSEUDO-SYNCHRONIZATION

We reveal sufficient evidences that for Am binaries the metallicity mi ght depend on their orbital periods, P-orb, rather than on v sin i. In particular. delta m(1) index seems to decrease with increasing orbita l period up to at least P-orb approximate to 50(d), probably even up t o P-orb approximate to 200(d). This gives further support to our ''tid al mixing + stabilization'' hypothesis formulated in Part I. Moreover, while the most metallic Am stars seem to have rather large periods th e slowest rotators are found to exhibit substantially shorter P-orb A questioning eye is thus cast on the generally adopted view that Am pec uliarity is caused by a suppressed rotationally induced mixing in slow ly rotating 'single' stars. The observed anticorrelation between rotat ion and metallic ity may have also other than the 'textbook' explanati on, namely being the result of the correlation between metallicity and orbital period, as the majority of Am binaries are possibly synchroni zed. We further argue that there is a tendency in Am binaries towards pseudo-synchronization up to P-orb approximate to 35(d). This has: how ever, no serious impact on our conclusions from Part I; on the contrar y, they still hold even if this effect is taken into account.