The VLT-FLAMES Tarantula Survey: Multiplicity and Dynamics of the Massive Stars in 30 Dor

Sana, H.; Dunstall, P. R.; Hénault-Brunet, V.; Walborn, N. R.; de Koter, A.; de Mink, S. E.; Dufton, P. L.; Evans, C. J.; Maíz Apellániz, J.; Taylor, W. D.; Vink, J. S.
Proceedings of a Scientific Meeting in Honor of Anthony F. J. Moffat held at Auberge du Lac Taureau, St-Michel-Des-Saints, Québec, Canada, held 11-15 July 2011. ASP Conference Series, Vol. 465. San Francisco: Astronomical Society of the Pacific, p.284 (2012).


We present the first results on the multiplicity and dynamics of the OB star population in 30 Dor obtained in the framework of the VLT-FLAMES Tarantula Survey. Based on their radial velocity (RV) variations, we have identified over 100 O-type and about 160 B-type spectroscopic binaries. The observed spectroscopic binary fraction for the O and B stars in our sample is of the order 30-35%. Preliminary considerations on the binary detection rate suggest a true spectroscopic binary fraction of the order of 50%. The overall RV dispersion (σRV) of the O stars in the complete sample is about 10 km s-1 but we note that the NGC 2060 and NGC 2070 regions show slightly different dynamical properties. We identified 17 O-type runaway candidates that show deviating RVs. One third of these candidates are On/nn/nnn stars, indicating a large rotational velocity. We show that the fast rotators have different RV properties than the average of the sample and are distributed throughout the field. This suggests a link between large rotation rate and peculiar RVs and, ultimately, the runaway phenomenon. Using the O stars observed within 25″(˜ 6 pc) from the core of R136, we obtain a preliminary upper limit of 7.5 km s-1 to σdyn. Given that this value has yet to be corrected down for contributions of non-detected long period binaries, this indicates that R136 is possibly a dynamically stable cluster.