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Lookup NU author(s): Dr Dominic BowmanORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© The Authors 2025. Context. Rapidly rotating classical OBe stars have been proposed as the products of binary interactions, and the fraction of Be stars with compact companions implies that at least some are. However, to constrain the interaction physics spinning up the OBe stars, a large sample of homogeneously analyzed OBe stars with well-determined binary characteristics and orbital parameters are required. Aims. We investigated the multiplicity properties of a sample of 18 Oe, 62 Be, and two Of?p stars observed within the BLOeM survey in the Small Magellanic Cloud. We analyzed the first nine epochs of spectroscopic observations obtained over approximately three months in 2023. Methods. Radial velocities (RVs) of all stars were measured using cross-correlation based on different sets of absorption and emission lines. Applying commonly used binarity criteria, we classified objects as binaries, binary candidates, and apparently single (RV stable) objects. We further inspected the spectra for double-lined spectroscopic binaries and cross-matched with catalogs of X-ray sources and photometric binaries. Results. We classify 14 OBe stars as binaries, and an additional 11 as binary candidates. The two Of?p stars are apparently single. We find two more objects that are most likely currently interacting binaries. Without those, the observed binary fraction for the remaining OBe sample of 78 stars is fOBeobs = 0.18 ± 0.04 (fOBeobs+cand = 0.32±0.05 including candidates). This binary fraction is less than half of that measured for OB stars in BLOeM. Combined with the lower fraction of SB2s, this suggests that OBe stars do indeed have fundamentally different present-day binary properties than OB stars. We find no evidence for OBe binaries with massive compact companions, in contrast to expectations from binary population synthesis. Conclusions. Our results support the binary scenario as an important formation channel for OBe stars, as post-interaction binaries may have been disrupted or the stripped companions of OBe stars are harder to detect. Further observations are required to characterize the detected binaries, their orbital parameters, and the nature of their companions.
Author(s): Bodensteiner J, Shenar T, Sana H, Britavskiy N, Crowther PA, Langer N, Lennon DJ, Mahy L, Patrick LR, Villasenor JI, Abdul-Masih M, Bowman DM, de Koter A, de Mink SE, Deshmukh K, Fabry M, Gilkis A, Gotberg Y, Holgado G, Izzard RG, Janssens S, Kalari VM, Keszthelyi Z, Kubat J, Mandel I, Maravelias G, Oskinova LM, Pauli D, Ramachandran V, Rocha DF, Renzo M, Sander AAC, Schneider FRN, Schootemeijer A, Sen K, Stoop M, Toonen S, van Loon JT, Valli R, Vigna-Gomez A, Vink JS, Wang C, Xu X-T
Publication type: Article
Publication status: Published
Journal: Astronomy and Astrophysics
Year: 2025
Volume: 698
Online publication date: 28/05/2025
Acceptance date: 10/01/2025
Date deposited: 16/06/2025
ISSN (print): 0004-6361
ISSN (electronic): 1432-0746
Publisher: EDP Sciences
URL: https://doi.org/10.1051/0004-6361/202452623
DOI: 10.1051/0004-6361/202452623
Data Access Statement: Tables C.1 and C.2 are available in electronic form at the CDS via anonymous ftp cdsarc.cds.unistra.fr (130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/698/A38. Appendices D, E and F are available via https://doi.org/10.5281/zenodo.14679548
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