The initial distribution of spin rates of massive stars is a fingerprint of their elusive formation process. It also sets a key initial condition for stellar evolution and is thus an important ingredient in stellar population synthesis. So far, most studies have focused on single stars. Oscar Ramirez-Agudelo, PhD student in Amsterdam, measured the rotation rates for 114 O-type binaries observed as part of the VLT FLAMES Tarantula Survey.
We find that the wide binaries have a distribution that is very similar to that of single stars. This is surprising as it seems to hint that binaries and single stars obtain their birth spin in similar ways. The big exception is the complete lack of very rapidly spinning stars among binary systems is consistent with the idea proposed in De Mink et al (2013) that most stars with v sin i > 300 km/s in the single star sample are spun-up post-binary interaction products.
Ramırez-Agudelo, Sana, de Mink et al. (2015) “VFTS XXI: Stellar spin rates of O-type spectroscopic binaries” accepted for publication in A&A.