Wind mass-loss rates of stripped stars inferred from Cygnus X-1

TL;DR

This paper proposes a formation scenario for Cygnus X-1 that accounts for its observed high masses and black hole spin, highlighting reduced wind mass loss in stripped stars based on system properties.

Contribution

It introduces a formation channel for Cygnus X-1 that aligns with observed masses and spins, emphasizing lower wind mass loss rates in stripped stars.

Findings

Higher masses for the companion star and black hole than previous estimates.

Black hole in Cygnus X-1 is nearly maximally spinning.

Reduced wind mass loss rates are necessary to match observed system properties.

Abstract

Recent observations of the high-mass X-ray binary Cygnus X-1 have shown that both the companion star (41 solar masses) and the black hole (21 solar masses) are more massive than previously estimated. Furthermore, the black hole appears to be nearly maximally spinning. Here we present a possible formation channel for the Cygnus X-1 system that matches the observed system properties. In this formation channel, we find that the orbital parameters of Cygnus X-1, combined with the observed metallicity of the companion, imply a significant reduction in mass loss through winds relative to commonly used prescriptions for stripped stars.