Issue |
A&A
Volume 690, October 2024
|
|
---|---|---|
Article Number | A289 | |
Number of page(s) | 22 | |
Section | Stellar atmospheres | |
DOI | https://doi.org/10.1051/0004-6361/202451586 | |
Published online | 17 October 2024 |
Binarity at LOw Metallicity (BLOeM)
A spectroscopic VLT monitoring survey of massive stars in the SMC★
1
The School of Physics and Astronomy, Tel Aviv University,
Tel Aviv
6997801
Israel
2
ESO – European Southern Observatory,
Karl-Schwarzschild-Strasse 2,
85748
Garching bei München,
Germany
3
Institute of Astronomy, KU Leuven,
Celestijnenlaan 200D,
3001
Leuven,
Belgium
4
Department of Physics & Astronomy, Hounsfield Road, University of Sheffield,
Sheffield
S3 7RH,
UK
5
Instituto de Astrofísica de Canarias, C. Vía Láctea, s/n,
38205
La Laguna, Santa Cruz de Tenerife,
Spain
6
Universidad de La Laguna, Dpto. Astrofísica, Av. Astrofśico Francisco Sánchez,
38206
La Laguna, Santa Cruz de Tenerife,
Spain
7
Escola de Ciências e Tecnologia, Universidade Federal do Rio Grande do Norte,
Natal,
RN
59072-970,
Brazil
8
Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut,
Mönchhofstr. 12–14,
69120
Heidelberg,
Germany
9
School of Mathematics, Statistics and Physics, Newcastle University,
Newcastle upon Tyne,
NE1 7RU,
UK
10
Heidelberger Institut für Theoretische Studien,
Schloss-Wolfsbrunnenweg 35,
69118
Heidelberg,
Germany
11
Universität Heidelberg, Department of Physics and Astronomy,
Im Neuenheimer Feld 226,
69120
Heidelberg,
Germany
12
Royal Observatory of Belgium,
Avenue Circulaire/Ringlaan 3,
1180
Brussels,
Belgium
13
Anton Pannekoek Institute for Astronomy, University of Amsterdam,
Science Park 904,
1098
XH
Amsterdam,
The Netherlands
14
Max-Planck-Institute for Astrophysics,
Karl-Schwarzschild-Strasse 1,
85748
Garching,
Germany
15
European Space Agency (ESA), ESA Office, Space Telescope Science Institute,
3700 San Martin Drive,
Baltimore,
MD
21218,
USA
16
ICREA,
Pg. Lluís Companys 23,
08010
Barcelona,
Spain
17
Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona (IEEC-UB),
Martí Franquès 1,
08028
Barcelona,
Spain
18
Institute of Astronomy, University of Cambridge,
Madingley Road,
Cambridge
CB3 0HA,
UK
19
Argelander-Institut für Astronomie, Universität Bonn,
Auf dem Hügel 71,
53121
Bonn,
Germany
20
Institute of Science and Technology Austria (ISTA),
Am Campus 1,
3400
Klosterneuburg,
Austria
21
Space Telescope Science Institute,
3700 San Martin Drive,
Baltimore,
MD
21218,
USA
22
Department of Astronomy and Physics, Saint Mary’s University,
923 Robie Street,
Halifax
B3H 3C3,
Canada
23
Gemini Observatory/NSF’s NOIRLab,
Casilla 603,
La Serena,
Chile
24
Center for Computational Astrophysics, Division of Science, National Astronomical Observatory of Japan,
2-21-1, Osawa, Mitaka,
Tokyo
181-8588,
Japan
25
Astronomical Institute, Academy of Sciences of the Czech Republic,
Fričova 298,
CZ-251 65
Ondřejov,
Czech Republic
26
Department of Astronomy and Astrophysics, University of Toronto,
50 St. George Street,
Toronto, Ontario,
M5S 3H4,
Canada
27
Dublin Institute for Advanced Studies, DIAS Dunsink Observatory,
Dunsink Lane,
Dublin 15,
Ireland
28
Centro de Astrobiología (CSIC-INTA), campus ESAC, camino bajo del castillo s/n,
28 692
Villanueva de la Cañada,
Spain
29
School of Physics and Astronomy, Monash University,
Clayton
VIC 3800,
Australia
30
ARC Centre of Excellence for Gravitational-wave Discovery (OzGrav),
Melbourne,
Australia
31
IAASARS, National Observatory of Athens,
15236
Penteli,
Greece
32
Institute of Astrophysics, FORTH,
71110
Heraklion,
Greece
33
Centro de Astrobiología (CSIC-INTA),
Ctra. Torrejón a Ajalvir km 4,
28850
Torrejón de Ardoz,
Spain
34
Institut für Physik und Astronomie, Universität Potsdam,
Karl-Liebknecht-Str. 24/25,
14476
Potsdam,
Germany
35
McWilliams Center for Cosmology & Astrophysics, Department of Physics, Carnegie Mellon University,
Pittsburgh,
PA
15213,
USA
36
Lund Observatory, Division of Astrophysics, Department of Physics, Lund University,
Box 43,
221 00,
Lund,
Sweden
37
Department of Astronomy & Steward Observatory,
933 N. Cherry Ave.,
Tucson,
AZ
85721,
USA
38
Observatório Nacional,
R. Gen. José Cristino, 77 – Vasco da Gama,
Rio de Janeiro,
RJ
20921-400,
Brazil
39
Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University,
Grudziadzka 5,
87–100
Torun,
Poland
40
Department of Particle Physics and Astrophysics, Weizmann Institute of Science,
Rehovot
7610001,
Israel
41
Lennard-Jones Laboratories, Keele University,
ST5 5BG,
UK
42
Center for Computational Astrophysics, Flatiron Institute,
New York,
NY
10010,
USA
43
Max-Planck-Institut für Astronomie,
Königstuhl 17,
69117
Heidelberg,
Germany
44
Armagh Observatory,
College Hill,
Armagh,
BT61 9DG,
Northern Ireland, UK
★★ Corresponding author; tshenar@tau.ac.il
Received:
19
July
2024
Accepted:
27
August
2024
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.
Key words: binaries: general / binaries: spectroscopic / stars: massive / Magellanic Clouds
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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