Maximum Black Hole Mass Across Cosmic Time

At the end of its life, a very massive star is expected to collapse into a black hole (BH). The recent detection of an 85 solar mass stellar BH from GW 190521 appears to present a fundamental problem as to how such heavy BHs exist above the approximately 50 solar mass pair-instability (PI) limit where stars are expected to be blown to pieces. We show that for stellar models with reasonable assumptions, 90-100 solar mass stars at reduced metallicity can produce Blue supergiant progenitors with core masses sufficiently small to remain below the second mass gap, yet at the same time lose an amount of mass small enough to end up in the range of an “impossible” 85 solar mass BH. We present a robust scenario that not only doubles the maximum stellar BH mass set by PI, but also allows us to probe the Maximum stellar BH mass as a function of metallicity and Cosmic time in a physically sound framework.