What Sets the Initial Rotation Rates of Massive Stars

摘要: The physical mechanisms that set the initial rotation rates in massive stars are a crucial unknown current star formation theory. Observations of young, provide evidence they form similar fashion to their low-mass counterparts. magnetic coupling between and its accretion disk may be sufficient spin down pre-main sequence (PMS) well below breakup at end stage when rate is low. However, we show these torques insufficient PMS due short times high rates. We develop model for angular momentum evolution over wide range mass, considering both gravitational torques. find unable either low or mass during main phase, cannot spun significantly by either. Spin-down occurs only if stars' lifetimes substantially longer fields much stronger than observations suggest.