7455 20250204104657.0 10.25518/0037-9565.11741 DOI SCART-2025-0086 Mahy, L Identifying Quiescent Compact Objects in Massive Galactic Single-lined Spectroscopic Binaries 2024 It is now clearly established that massive stars are predominantly found in multiple systems. While their period and eccentricity distributions are now well established across different metallicity regimes, the mass-ratio distribution has been mostly limited to double-lined spectroscopic binaries. The mass-ratio distribution therefore remains subject to significant uncertainties and open questions encompass the shape and extend of the companion mass-function towards its low-mass end and the nature of undetected companions in single-lined spectroscopic binaries, i.e. low-mass main-sequence stars, binary interaction products, compact objects, etc. We have conducted a large and systematic analysis of a sample of more than 80 single-line O-type spectroscopic binaries in the Milky Way and in the Large Magellanic Cloud using a sophisticated multi-technique, and multi-wavelength approach. We report on the developed methodology, the constraints obtained on the nature of SB1 companions, the distribution of O star mass-ratios at LMC metallicity and the occurrence of quiescent OB+black hole binaries. NO Bulletin de la Société Royale des Sciences de Liège 93 2024 2 437-444 laurent.mahy@ksb-orb.be 193340 http://publi2-as.oma.be/record/7455/files/Mahy_bsrsl_2024.pdf 2939 http://publi2-as.oma.be/record/7455/files/Mahy_bsrsl_2024.jpg?subformat=icon-180 icon-180 3185 http://publi2-as.oma.be/record/7455/files/Mahy_bsrsl_2024.gif?subformat=icon icon published in REFERD