GW150914: Spin based constraints on the merger time of the progenitor system

Understand

We explore the implications of the observed low spin of GW150914 within the context of stellar astrophysics and progenitor models.

• We conclude that many of the recently proposed scenarios are in marked tension with this observation.
• We derive a simple model for the observed spin in the case that the progenitor system was a field binary composed of a black hole (BH) and a Wolf-Rayet star and explore the implications of the observed spin for this model.
• The spin observation allows us to place a lower limit for the delay time between the formation of the BH+BH binary and the actual merger, $t_{\textrm{merge}}$.