The evolutionary status of the black hole candidate V404 Cygni

I show that the black hole candidate system V404 Cygni conforms to a simple picture of stripped-giant’ evolution, in which an evolved secondary star of core mass Mc~ 0.20–0.22 Mʘ overflows its Roche lobe. The predicted absolute magnitudes for this star give system distances of 3.5–5.1 kpc and peak X-ray luminosities Lx~ 1.8–3. 7 5 × 1039erg s–1. The mass-transfer rates predicted by the evolutionary picture agree well with X-ray observations.