Formation of black holes in the pair-instability mass gap: Evolution of a post-collision star. Issue 1 (6th August 2022)

• Record Type: Journal Article
• Authors: Costa, Guglielmo; Ballone, Alessandro; Mapelli, Michela; Bressan, Alessandro
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 516:Issue 1(2022)
• Page Start: 1072
• Page End: 1080
• Publication Date: 2022-08-06
• Subjects: black hole physics -- stars: black holes -- stars: evolution -- stars: massive; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac2222
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: The detection of GW190521 by the LIGO–Virgo collaboration has revealed the existence of black holes (BHs) in the pair-instability (PI) mass gap. Here, we investigate the formation of BHs in the PI mass gap via star–star collisions in young stellar clusters. To avoid PI, the stellar-collision product must have a relatively small core and a massive envelope. We generate our initial conditions from the outputs of a hydrodynamical simulation of the collision between a core helium burning star (∼58 M⊙ ) and a main-sequence star (∼42 M⊙ ). The hydrodynamical simulation allows us to take into account the mass lost during the collision (∼12 M⊙ ) and to build the chemical composition profile of the post-collision star. We then evolve the collision product with the stellar evolution codes parsec and mesa . We find that the post-collision star evolves through all the stellar burning phases until core collapse, avoiding PI. At the onset of core collapse, the post-collision product is a blue supergiant star. We estimate a total mass-loss of about 1 M⊙ during the post-collision evolution, due to stellar winds and shocks induced by neutrino emission in a failed supernova. The final BH mass is ≈87 M⊙ . Therefore, we confirm that the collision scenario is a suitable formation channel to populate the PI mass gap.