The chemical fingerprint of the Gaia BH3 system

Le résumé fourni par la source

Context. The Gaia BH3 system hosts the most massive known stellar-origin black hole and a low-mass metal-poor companion whose chemical composition may help us constrain early explosive nucleosynthesis processes. Aims. We investigated the chemical abundances of the companion in order to place constraints on the formation history of this remarkable system. Methods. We performed a detailed analysis of high-resolution ESO-UVES spectra of the companion. 51 elements from lithium to uranium were investigated through spectral synthesis, including 15 treated in non-local thermodynamic equilibrium. We compared the resulting pattern to r -process-enriched stars, to nucleosynthesis models, and to stars of the ED-2 stream, from which BH3 is thought to originate. Results. The abundance pattern of the BH3 companion is consistent with that of r-I stars and is well reproduced by a combination of core-collapse supernova yields and an r -process component. The chemical patterns of four ED-2 stars closely match that of the companion, particularly after accounting for different levels of mixing of the enriched material with the ambient gas. Conclusions. The present analysis provides the most detailed chemical characterisation of a metal-poor star associated with a stellar-mass black hole. The chemical similarity with ED-2 stars argue against local pollution across the binary system. The abundances instead reflect an early spatially inhomogeneous enrichment of the progenitor cluster.

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