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

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 ΔH < 4 and ΔH < 5, respectively. Taking advantage of NACO's field of view, we further uniformly searched for visual companions in an 8'' radius down to ΔH = 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 objectsmore » in our main sample (δ < 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 ρ < 8'' increases to f {sub 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 {sub 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.« less
Authors:
 [1] ; ; ;  [2] ; ; ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9] ;  [10] ;  [11]
  1. European Space Agency/Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
  2. Université Grenoble Alpes, IPAG, F-38000 Grenoble (France)
  3. LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot, Paris Sciences et Lettres, 5 Place Jules Janssen, F-92195 Meudon (France)
  4. European Southern Observatory, Schwarzschild-Str. 2, D-85748 Garching bei München (Germany)
  5. Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia)
  6. Max-Planck-Institut für Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany)
  7. Département d'Astrophysique, Géophysique et Océanographie, Université de Liège, 17 Allée du Six Août, B-4000 Liège (Belgium)
  8. Astrophysical Institute Anton Pannekoek, Universiteit van Amsterdam, Science Park 904, 1098XH Amsterdam (Netherlands)
  9. JILA, 440 UCB, University of Colorado, Boulder, CO 80309-0440 (United States)
  10. Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam (Germany)
  11. Deutsches SOFIA Instituut, SOFIA Science Center, NASA Ames Research Center, Mail Stop N232-12, Moffett Field, CA 94035 (United States)
Publication Date:
OSTI Identifier:
22340138
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal, Supplement Series; Journal Volume: 215; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BRIGHTNESS; CATALOGS; COLLISIONS; DATA ANALYSIS; DETECTION; ECLIPSE; EMISSION; LUMINOSITY; MULTIPLICITY; RADIOWAVE RADIATION; SPATIAL RESOLUTION; STARS; STELLAR WINDS