The formation of dormant black hole binaries: a key to mass transfer and stellar dynamics

• Applicant: Professorin Dr. Michela Mapelli
• Subject Area: Astrophysics and Astronomy
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 546850815

Recent spectroscopic and astrometric measurements open a new window on dormant black holes, members of detached binary systems with a stellar companion. These yield complementary information to binary black hole mergers and represent a faithful portrait of black hole populations in the local Universe. The two systems detected thanks to Gaia, Gaia BH1 and BH2, pose a number of questions on the formation of dormant black holes: their orbital periods are at the same time too short to have evolved without mass transfer and too long for the traditional common-envelope formalism. The near zero eccentricity in VFTS 243 is difficult to reconcile with natal kicks, while the two candidates in NGC3201 have important implications for the dynamics of black holes in globular clusters. DoBlack will explore the formation of dormant black holes by means of dedicated binary evolution models and N-body simulations of star clusters. We will perform a large set of population synthesis simulations, probing the impact of the mass transfer stability criterion, accretion efficiency, angular momentum transport, natal kicks and common-envelope formalism. Our preliminary, idealised tests show that conservative stable mass transfer naturally leads to the formation of Gaia BH1-like systems. We will also explore the evolution of black holes in open and globular clusters with new, up-to-date direct N-body simulations. Finally, we will predict the population of dormant black holes in the Milky Way by exploiting an observationally calibrated Besancon model. Our simulations will have key implications for massive binary evolution and stellar dynamics, and will provide a benchmark for future spectroscopic surveys, as well as the interpretation of the Gaia Data Release 4.

• DFG Programme: Research Grants