2010ApJ...719..287L

Modeling the rotation history of solar-type stars is an outstanding problem in modern astrophysics. One of the main challenges is to explain the dispersion in the distribution of stellar rotation rate for young stars. Previous works have advocated diverse mechanisms to explain the presence of fast rotators (FRs) and also of slow rotators (SRs). For instance, dynamo saturation can limit the stellar spin-down and explain the presence of FRs but does not produce enough SRs. Here, we present a new model that can account for the presence of both types of rotators by incorporating fluctuations in the angular momentum loss. This renders the spin-down problem probabilistic in nature, some stars experiencing more braking on average than others. We show that random fluctuations in the loss of angular momentum enhance the population of both FR and SR compared to the deterministic cases (with a linear dynamo prescription or with dynamo saturation). The stochastic angular momentum loss thus provides an alternative physical mechanism to that of a saturated dynamo, with an even better agreement with observations.