Sparse Aperture Masking of Massive Stars

H. Sana [1], S. Lacour [2], J.-B. Le Bouquin [3], A. de Koter [1,4], C. Moni Bidin [5], L. Muijres[1], O. Schnurr[6], H. Zinnecker [7,8]

1. Astronomical Institute `Anton Pannekoek', University of Amsterdam, Postbus 94249, 1090 GE, Amsterdam, The Netherlands
2. LESIA, Observatoire de Paris, Universite Paris Diderot, Meudon, France
3. Institut de Planetologie et d'Astrophysique de Grenoble (IPAG), France
4. Astronomical Institute, Utrecht University, Utrecht, The Netherlands
5. Departamento de Astronomia, Universidad de Concepcion, Chile
6. Leibniz-Institut für Astrophysik Potsdam (AIP), Potsdam, Germany
7. Deutsches SOFIA Institute, Stuttgart, Germany
8. SOFIA Science Center, NASA-Ames Research Center, Moffett Field, CA, USA

We present the earliest results of our NACO/VLT sparse aperture masking (SAM) campaign to search for binarity in a sample of 60 O-type stars. We detect Delta Ks < 5 mag companions for 20-25% of our targets with separations in the range 30-100 mas (typically, 40 - 200 A.U.). Most of these companions were unknown, shedding thus new light on the multiplicity properties of massive stars in a separation and brightness regime that has been difficult to explore so far. Adding detections from other techniques (spectroscopy, interferometry, speckle, lucky imaging, AO), the fraction of O stars with at least one companion is 85% (51/60 targets). This is the largest multiplicity fraction ever found.

Reference: To be published in the proceedings of the meeting 'Four decades of research on massive stars' in honor of Tony Moffat, 11-15 July 2011, Saint-Michel-des-Saints, Quebec
Status: Conference proceedings