Revisiting the evolutionary status of massive stars in the central parsec of the Milky Way

¹ Astronomický ústav, Akademie věd Ceské republiky Fričova 298 251 65 Ondřejov, Czech Republic
² Departamento de Ciencias, Facultad de Artes Liberales, Universidad Adolfo Ibáñez Av. Padre Hurtado 750 Viña del Mar, Chile
³ Department of Astronomy, University of Geneva Chemin Pegasi 51 1290 Versoix, Switzerland
⁴ Millennium Nucleus on Transversal Research and Technology to Explore Supermassive Black Holes (TITANS), Gran Bretaña 1111 Playa Ancha Valparaíso, Chile

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 15 August 2025
Accepted: 8 December 2025

Abstract

Context. Massive stars and their winds strongly affect their environment. For example, they determine the accretion rate on to the Galactic centre (GC) supermassive black hole Sagittarius A* (Sgr A*). The winds of these stars collide and are accreted at a rate that depends on their chemical composition. The new self-consistent approach to modelling stellar winds of these stars also leads to lower mass-loss rates compared to previous standard values, and it thus alters the stellar properties of their advanced evolutionary stages.

Aims. We revisit the evolutionary status of the evolved massive stars in the GC by means of new tracks based on updated mass-loss rate recipes for the earlier stages of massive stars.

Methods. We used the Geneva evolution code for initial stellar masses ranging from 20 to 60 M_⊙ for a metallicity Z = 0.020. We adopted a new mass-loss rate recipe for the line-driven winds of O-type stars and B supergiants, and a new recipe for the dust-driven winds of red supergiants (RSG). Additionally, we set up an initial rotation Ω/Ω_crit = 0.4, and we adopted the Ledoux criterion for the treatment of convection in inner layers.

Results. We found that evolution models with the new mass-loss rate prescriptions predict that stars lose fewer of their outer layers during their initial phases, while the mass is strongly reduced in the RSG phase. As a consequence, the resulting Wolf-Rayet (WR) stars are less radially homogeneous in their inner structure from the core to the surface. These new evolution models also predict the absence of hydrogen-free WN stars. These evolutionary predictions agree better with the observed properties of the WR stars in the GC, in particular, with their chemical abundances.

Conclusions. We provide a table with the chemical H, He, and CNO abundances calculated for the different subtypes of WR stars (Ofpe/WN9, WNL, WN/C, and WC). We propose a different re-arrangement of the WR subtypes to be used for modelling the collision of their winds. We discuss the potential implications of these changes for the colliding winds generated by massive stars in the GC, which accrete onto the supermassive black hole Sgr A*.