We present a model for the rotational evolution of a young , solar-mass star interacting magnetically with an accretion disk .
As in a previous paper ( Paper I ) , the model includes changes in the star ’ s mass and radius as it descends the Hayashi track , a decreasing accretion rate , and a prescription for the angular momentum transfer between the star and disk .
Paper I concluded that , for the relatively strong magnetic coupling expected in real systems , additional processes are necessary to explain the existence of slowly rotating pre-main-sequence stars .
In the present paper , we extend the stellar spin model to include the effect of a spin-down torque that arises from an accretion-powered stellar wind .
For a range of magnetic field strengths , accretion rates , initial spin rates , and mass outflow rates , the modeled stars exhibit rotation periods within the range of 1–10 days in the age range of 1–3 Myr .
This range coincides with the bulk of the observed rotation periods , with the slow rotators corresponding to stars with the lowest accretion rates , strongest magnetic fields , and/or highest stellar wind mass outflow rates .
We also make a direct , quantitative comparison between the accretion-powered stellar wind scenario and the two types of disk-locking models ( namely the X-wind and Ghosh & Lamb type models ) and identify some remaining theoretical issues for understanding young star spins .