A black hole detected in the young massive LMC cluster NGC 1850

• Published in: Monthly notices of the Royal Astronomical Society Vol. 511; no. 2; pp. 2914 - 2924
• Main Authors: Saracino, S, Kamann, S, Guarcello, M G, Usher, C, Bastian, N, Cabrera-Ziri, I, Gieles, M, Dreizler, S, Da Costa, G S, Husser, T-O, Hénault-Brunet, V
• Format: Journal Article
• Language: English
• Published: Oxford University Press 16.02.2022
• Subjects: binaries: spectroscopic; galaxies: photometry; globular clusters: individual: NGC 1850; techniques: imaging spectroscopy; techniques: radial velocities; globular clusters: individual: NGC 1850; binaries: spectroscopic; techniques: radial velocities; galaxies: photometry; techniques: imaging spectroscopy
• ISSN: 0035-8711; 1365-2966; 1365-2966
• DOI: 10.1093/mnras/stab3159

ABSTRACT We report on the detection of a black hole (NGC 1850 BH1) in the ∼100-Myr-old massive cluster NGC 1850 in the Large Magellanic Cloud. It is in a binary system with a main-sequence turn-off star (4.9 ± 0.4 M⊙), which is starting to fill its Roche lobe and is becoming distorted. Using 17 epochs of Very Large Telescope/Multi-Unit Spectroscopic Explorer observations, we detected radial velocity variations exceeding 300 km s−1 associated with the target star, linked to the ellipsoidal variations measured by the fourth phase of the Optical Gravitational Lensing Experiment in the optical bands. Under the assumption of a semidetached system, the simultaneous modelling of radial velocity and light curves constrains the orbital inclination of the binary to 38° ± 2°, resulting in a true mass of the unseen companion of $11.1_{-2.4}^{+2.1}\,{\rm M}_{\odot }$. This represents the first direct dynamical detection of a black hole in a young massive cluster, opening up the possibility of studying the initial mass function and the early dynamical evolution of such compact objects in high-density environments.