Belczynski, K.K.BelczynskiHirschi, R.R.HirschiKaiser, E. A.E. A.KaiserLiu, JifengJifengLiuCasares, J.J.CasaresLu, YoujunYoujunLuO'Shaughnessy, R.R.O'ShaughnessyHeger, A.A.HegerJustham, S.S.JusthamSORIA, RobertoRobertoSORIA2025-03-112025-03-1120200004-637Xhttp://hdl.handle.net/20.500.12386/36642A 70 ${M}_{\odot }$ black hole (BH) was discovered in the Milky Way disk in a long-period detached binary system (LB-1) with a high-metallicity 8 ${M}_{\odot }$ B star companion. Current consensus on the formation of BHs from high-metallicity stars limits the BH mass to be below 20 ${M}_{\odot }$ due to strong mass loss in stellar winds. Using analytic evolutionary formulae, we show that the formation of a 70 ${M}_{\odot }$ BH in a high-metallicity environment is possible if wind mass-loss rates are reduced by factor of five. As observations indicate, a fraction of massive stars have surface magnetic fields that may quench the wind mass-loss, independently of stellar mass and metallicity. We confirm such a scenario with detailed stellar evolution models. A nonrotating 85 ${M}_{\odot }$ star model at Z = 0.014 with decreased winds ends up as a 71 ${M}_{\odot }$ star prior to core collapse with a 32 ${M}_{\odot }$ He core and a 28 ${M}_{\odot }$ CO core. Such a star avoids the pair-instability pulsation supernova mass loss that severely limits BH mass and may form a ∼70 ${M}_{\odot }$ BH in the direct collapse. Stars that can form 70 ${M}_{\odot }$ BHs at high Z expand to significant sizes, with radii of R ≳ 600 ${R}_{\odot }$ , however, exceeding the size of the LB-1 orbit. Therefore, we can explain the formation of BHs up to 70 ${M}_{\odot }$ at high metallicity and this result is valid whether or not LB-1 hosts a massive BH. However, if LB-1 hosts a massive BH we are unable to explain how such a binary star system could have formed without invoking some exotic scenarios.STAMPAenArticle10.3847/1538-4357/ab6d772-s2.0-85081624743https://api.elsevier.com/content/abstract/scopus_id/85081624743https://iopscience.iop.org/article/10.3847/1538-4357/ab6d772020ApJ...890..113BFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation