Rotational velocities of early-type binaries

We find correlations in the case of close binaries which suggest that tidal synchronization is effective for binaries whose separation exceeds the stellar radius by more than an order of magnitude, in line with the theoretical predictions of Goldreich & Nicholson (1989ApJ...342.1079G) and the previous observational analysis of Giuricin et al. (1984A&A...135..393G).

In the case of wide binaries, the vsin(i) values are not well correlated, which requires that the magnitude of the spin speeds is not tightly correlated. Under this assumption, we then find that the data provide no significant constraints on the degree of alignment of spin axes. The data are therefore compatible with scenarios (such as disc fragmentation or capture) which differ widely in the expected degree of spin alignment.