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SOUTHERN MASSIVE STARS AT HIGH ANGULAR RESOLUTION: OBSERVATIONAL CAMPAIGN AND COMPANION DETECTION

H. SanaEuropean Space Agency/Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA;J.-B. Le BouquinCNRS, IPAG, F-38000 Grenoble, FranceS. LacourLESIA, Observatoire de Paris, CNRS, UPMC, Universit Paris-Diderot, Paris Sciences et Lettres, 5 Place Jules Janssen, F-92195 Meudon, FranceJ.-P. BergerEuropean Southern Observatory, Schwarzschild-Str. 2, D-85748 Garching bei Mnchen, GermanyG. DuvertCNRS, IPAG, F-38000 Grenoble, FranceL. GauchetLESIA, Observatoire de Paris, CNRS, UPMC, Universit Paris-Diderot, Paris Sciences et Lettres, 5 Place Jules Janssen, F-92195 Meudon, FranceB. NorrisSydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006, AustraliaJ. OlofssonMax-Planck-Institut fr Astronomie, Koenigstuhl 17, D-69117 Heidelberg, GermanyD. PickelObservatoire de ParisG. ZinsCNRS, IPAG, F-38000 Grenoble, FranceO. AbsilDpartement d'Astrophysique, Gophysique et Ocanographie, Universit de Lige, 17 Alle du Six Aot, B-4000 Lige, BelgiumA. de KoterAstrophysical Institute Anton Pannekoek, Universiteit van Amsterdam, Science Park 904, 1098XH Amsterdam, The NetherlandsK. KratterO. SchnurrLeibniz-Institut fr Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam, GermanyH. ZinneckerDeutsches SOFIA Instituut, SOFIA Science Center, NASA Ames Research Center, Mail Stop N232-12, Moffett Field, CA 94035, USA

2014en

ABI

Annotatsiya

Multiplicity is one of the most fundamental observable properties of massive O-type stars and offers a promising way to discriminate between massive star formation theories. Nevertheless, companions at separations between 1 and 100 milliarcsec (mas) remain mostly unknown due to intrinsic observational limitations. At a typical distance of 2 kpc, this corresponds to projected physical separations of 2-200 AU. The Southern MAssive Stars at High angular resolution survey (smash+) was designed to fill this gap by providing the first systematic interferometric survey of Galactic massive stars. We observed 117 O-type stars with VLTI/PIONIER and 162 O-type stars with NACO/ Sparse Aperture Masking (SAM), probing the separation ranges 1-45 and 30-250 mas and brightness contrasts of H < 4 and H < 5, respectively. Taking advantage of NACO's field of view, we further uniformly searched for visual companions in an 8 radius down to H = 8. This paper describes observations and data analysis, reports the discovery of almost 200 new companions in the separation range from 1 mas to 8 and presents a catalog of detections, including the first resolved measurements of over a dozen known long-period spectroscopic binaries. Excluding known runaway stars for which no companions are detected, 96 objects in our main sample ( < 0 ; H < 7.5) were observed both with PIONIER and NACO/SAM. The fraction of these stars with at least one resolved companion within 200 mas is 0.53. Accounting for known but unresolved spectroscopic or eclipsing companions, the multiplicity fraction at separation < 8 increases to f m = 0.91 0.03. The fraction of luminosity class V stars that have a bound companion reaches 100% at 30 mas while their average number of physically connected companions within 8 is f c = 2.2 0.3. This demonstrates that massive stars form nearly exclusively in multiple systems. The nine non-thermal radio emitters observed by smash+ are all resolved, including the newly discovered pairs HD 168112 and CPD-47 2963. This lends strong support to the universality of the wind-wind collision scenario to explain the non-thermal emission from O-type stars.

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DOI: 10.1088/0067-0049/215/1/15

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