Binarity at LOw Metallicity (BLOeM)

The Binarity at LOw Metallicity (BLOeM) survey is an ESO large programme designed to obtain multi-epoch spectroscopy for 929 massive stars in the Small Magellanic Cloud (SMC). It will provide binary fractions and orbital configurations of binary systems and search for dormant black hole binary candidates (OB+BH). We present projected rotational velocities ( v sin i ) of all sources, and, using the multiplicity properties presented in previous papers, we derive the v sin i distributions of apparent single stars, single-lined spectroscopic (SB1) binaries, and SB2 systems. We identify a locus in the Hertzsprung-Russell diagram where rotational velocities decrease significantly; we interpret this feature as broadly corresponding to the terminal-age main sequence. The main-sequence cohort is distinguished by a broad range of v sin i values, but with a strong peak in the distribution in the range 30–60 km s −1 , which is close to the resolution limit of ∼30 km s −1 , indicating the presence of many upper limits. Sources in this low v sin i peak are distributed throughout the main sequence and are also present in the SB1 sample, though less prominent than in the single-star distribution. A preliminary analysis of the lowest v sin i cohort, which includes SB1 systems, implies that roughly one-third may be nitrogen rich, and we speculate that this cohort is a mix of pristine single stars, long-period binaries, and merger products. The SB2 systems appear to be mostly short-period binaries in synchronous rotation, and their v sin i estimates are distributed around a mean value of ∼140 km s −1 . Higher v sin i sources are also present in the single and SB1 systems, all of which have a tail to higher v sin i values. This is consistent with tidal and mass-transfer effects. The supergiants, with a few exceptions, have low v sin i , and the bulk of these systems is essentially unresolved at the current spectral resolution (∼30 km s −1 ).

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Publication Details

Journal
Astronomy and Astrophysics
Published
2026-01-30
DOI
https://doi.org/10.1051/0004-6361/202558539
Primary Topic
Stellar, planetary, and galactic studies
Type
article
Field-Weighted Citation Impact
0.00

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article

Binarity at LOw Metallicity (BLOeM)

D. M. Bowman, L. Mahy, J. Kubát, J. Bodensteiner et al.
Astronomy and Astrophysics
Stellar, planetary, and galactic studies
article

Binarity at LOw Metallicity (BLOeM)

D. M. Bowman, L. Mahy, J. Kubát, J. Bodensteiner, A. de Koter, M. Pawlak, P. L. Dufton, N. Langer, M. Stoop, Pablo Marchant, D. J. Lennon, X. -T. Xu, A. Alonso‐Herrero, S. Simon-Diaz, G. Holgado, S. R. Berlanas, J. Bestenlehner, N. Britavskiy, F. Najarro, M. Renzo, Ruggero Valli, D. F. Rocha, Alexey Bobrick, L. R. Patrick, A. S. Menon, K. Deshmukh, P. Crowther, T. Shenar, A. A. C. Sander, C. Wang, M. Gull, C. J. Evans, D. Pauli, Harim Jin, J. S. Vink, J. Villaseñor, A. Schootemeijer, Z. Z. Katabi, T. Sayada
article en

Abstract

The Binarity at LOw Metallicity (BLOeM) survey is an ESO large programme designed to obtain multi-epoch spectroscopy for 929 massive stars in the Small Magellanic Cloud (SMC). It will provide binary fractions and orbital configurations of binary systems and search for dormant black hole binary candidates (OB+BH). We present projected rotational velocities ( v sin i ) of all sources, and, using the multiplicity properties presented in previous papers, we derive the v sin i distributions of apparent single stars, single-lined spectroscopic (SB1) binaries, and SB2 systems. We identify a locus in the Hertzsprung-Russell diagram where rotational velocities decrease significantly; we interpret this feature as broadly corresponding to the terminal-age main sequence. The main-sequence cohort is distinguished by a broad range of v sin i values, but with a strong peak in the distribution in the range 30–60 km s −1 , which is close to the resolution limit of ∼30 km s −1 , indicating the presence of many upper limits. Sources in this low v sin i peak are distributed throughout the main sequence and are also present in the SB1 sample, though less prominent than in the single-star distribution. A preliminary analysis of the lowest v sin i cohort, which includes SB1 systems, implies that roughly one-third may be nitrogen rich, and we speculate that this cohort is a mix of pristine single stars, long-period binaries, and merger products. The SB2 systems appear to be mostly short-period binaries in synchronous rotation, and their v sin i estimates are distributed around a mean value of ∼140 km s −1 . Higher v sin i sources are also present in the single and SB1 systems, all of which have a tail to higher v sin i values. This is consistent with tidal and mass-transfer effects. The supergiants, with a few exceptions, have low v sin i , and the bulk of these systems is essentially unresolved at the current spectral resolution (∼30 km s −1 ).

Astronomy and AstrophysicsVol. 707
California Institute of Technology (US), Australian Research Council (AU), University of Bonn (DE), Tel Aviv University (IL), Shanghai Jiao Tong University (CN), Lund University (SE), Carnegie Institution for Science (US), Heidelberg University (DE), Royal Observatory of Belgium (BE), Armagh Observatory & Planetarium (GB), Czech Academy of Sciences, Astronomical Institute (CZ), European Space Agency (FR), Ghent University (BE), Ministry of Education (CL), Max Planck Institute for Astrophysics (DE), Max Planck Institute for Astronomy (DE), Institute of Astronomy (RU), Forschungsstätte der Evangelischen Studiengemeinschaft (DE), ARC Centre of Excellence for Gravitational Wave Discovery (AU), Centro de Astrobiología (ES), Instituto de Astrofísica de Canarias (ES), Astronomical Institute of the Slovak Academy of Sciences (SK), Astronomy and Space (AU), Geophysical Laboratory (US), Astronomical Observatory (RS), Laboratório Nacional de Astrofísica (BR), Institute of Natural Science (KP), Monash University (AU), Newcastle University (GB), Nanjing University (CN), University of Amsterdam (NL), University of Sheffield (GB), Netherlands Institute for Radio Astronomy (NL), KU Leuven (BE)
National Science Foundation, Comunidad de Madrid, Government of the United Kingdom, UK Research and Innovation, Ministerio de Ciencia, Innovación y Universidades, European Commission, Deutsche Forschungsgemeinschaft, Fonds Wetenschappelijk Onderzoek, Israel Science Foundation, Ministerio de Ciencia e Innovación, Bundesministerium für Wirtschaft und Energie, Fundación Bancaria Caixa d'Estalvis i Pensions de Barcelona, HORIZON EUROPE Framework Programme, European Regional Development Fund, Agencia Estatal de Investigación, Kavli Institute for Theoretical Physics, University of California, Santa Barbara
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Stellar, planetary, and galactic studies
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