Binarity at LOw Metallicity (BLOeM): A spectroscopic VLT monitoring survey of massive stars in the SMC

T. Shenar*, J. Bodensteiner, H. Sana, P. A. Crowther, D. J. Lennon, M. Abdul-Masih, L. A. Almeida, F. Backs, S. R. Berlanas, M. Bernini-Peron, J. M. Bestenlehner, D. M. Bowman, V. A. Bronner, N. Britavskiy, A. De Koter, S. E. De Mink, K. Deshmukh, C. J. Evans, M. Fabry, M. GielesA. Gilkis, G. González-Torà, G. Gräfener, Y. Götberg, C. Hawcroft, V. Hénault-Brunet, A. Herrero, G. Holgado, S. Janssens, C. Johnston, J. Josiek, S. Justham, V. M. Kalari, Z. Z. Katabi, Z. Keszthelyi, J. Klencki, J. Kubát, B. Kubátová, N. Langer, R. R. Lefever, B. Ludwig, J. MacKey, L. Mahy, J. Maíz Apellániz, I. Mandel, G. Maravelias, P. Marchant, A. Menon, F. Najarro, L. M. Oskinova, A. J.G. O'Grady, R. Ovadia, L. R. Patrick, D. Pauli, M. Pawlak, V. Ramachandran, M. Renzo, D. F. Rocha, A. A.C. Sander, T. Sayada, F. R.N. Schneider, A. Schootemeijer, E. C. Schösser, C. Schürmann, K. Sen, S. Shahaf, S. Simón-Díaz, M. Stoop, S. Toonen, F. Tramper, J. Th Van Loon, R. Valli, L. A.C. Van Son, A. Vigna-Gómez, J. I. Villaseñor, J. S. Vink, C. Wang, R. Willcox

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

Surveys in the Milky Way and Large Magellanic Cloud have revealed that the majority of massive stars will interact with companions during their lives. However, knowledge of the binary properties of massive stars at low metallicity, and therefore in conditions approaching those of the Early Universe, remain sparse. We present the Binarity at LOw Metallicity (BLOeM) campaign, an ESO large programme designed to obtain 25 epochs of spectroscopy for 929 massive stars in the Small Magellanic Cloud, allowing us to probe multiplicity in the lowest-metallicity conditions to date (Z = 0.2 Z). BLOeM will provide (i) the binary fraction, (ii) the orbital configurations of systems with periods of P ≲ 3 yr, (iii) dormant black-hole binary candidates (OB+BH), and (iv) a legacy database of physical parameters of massive stars at low metallicity. Main sequence (OB-type) and evolved (OBAF-type) massive stars are observed with the LR02 setup of the GIRAFFE instrument of the Very Large Telescope (3960- 4570 Å resolving power R = 6200; typical signal-to-noise ratio(S/N) ≈70- 100). This paper utilises the first nine epochs obtained over a three-month time period. We describe the survey and data reduction, perform a spectral classification of the stacked spectra, and construct a Hertzsprung-Russell diagram of the sample via spectral-type and photometric calibrations. Our detailed classification reveals that the sample covers spectral types from O4 to F5, spanning the effective temperature and luminosity ranges 6.5 ≲ Teff/kK ≲ 45 and 3.7 < log L/L < 6.1 and initial masses of 8 ≲ Mini ≲ 80 M. The sample comprises 159 O-type stars, 331 early B-type (B0- 3) dwarfs and giants (luminosity classes V- III), 303 early B-type supergiants (II- I), and 136 late-type BAF supergiants. At least 82 stars are OBe stars: 20 O-type and 62 B-type (13% and 11% of the respective samples). In addition, the sample includes 4 high-mass X-ray binaries, 3 stars resembling luminous blue variables, 2 bloated stripped-star candidates, 2 candidate magnetic stars, and 74 eclipsing binaries.

Original languageEnglish
Article numberA289
JournalAstronomy and Astrophysics
Volume690
DOIs
StatePublished - 1 Oct 2024

Funding

FundersFunder number
NextGeneration EU
Ministerio de Ciencia e Innovación
PRTR
Narodowa Agencja Wymiany Akademickiej
State Research Agency
Bundesministerium für Bildung und Forschung
Bundesministerium für Wirtschaft und Klimaschutz
Spanish Government Ministerio de Ciencia e Innovación
MICIN
Baden-Württemberg Ministry of Science
Royal Society-Science Foundation Ireland
International Space Science Institute
European Research Council
Horizon 2020
UK Research and Innovation
Consejo Superior de Investigaciones Científicas2022-AEP 005, BPN/BEK/2022/1/00106
ERC Horizon Europe funding guaranteeEP/Y031059/1
Horizon 2020 Framework Programme772225
Agència de Gestió d'Ajuts Universitaris i de Recerca772086
HORIZON EUROPE Framework Programme101044048
Narodowe Centrum NaukiOPUS 2021/41/B/ST9/00757
Agencia Estatal de InvestigaciónPID2022-136640 NB-C22, 10.13 039/501 100 011 033
Al-Mustafa International UniversityUNI/551/2021, PID2022-137779OB-C41, PID2019-105552RB-C41
Deutsche Forschungsgemeinschaft445674056, SA4064/1-1, Project-ID 496854903, SA4064/2-1
Deutsches Zentrum für Luft- und RaumfahrtEXC 2181/1-390900948, FKZ 50OR2005, ST/V000233/1, 50 OR 2306, 945806, ERC-2021-ADG101054731, 443790621
Science and Technology Facilities CouncilST/V000853/1
European Regional Development FundCEX2019-000918-M, PID2021-125485NB-C22, SGR-2021-01069
Australian Research CouncilCE230100016
Fonds Wetenschappelijk Onderzoek11E1721N
Japan Society for the Promotion of Science23K19071
Royal SocietyURF\R1\231631
CAPES-BrSEI-260003/001630/2023, FAPERJ/DSC-10

    Keywords

    • Binaries: general
    • Binaries: spectroscopic
    • Magellanic Clouds
    • Stars: massive

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