Gravitational slingshot of young massive stars in Orion.
CHATTERJEE S. and TAN J.C.
Abstract (from CDS):
The Orion Nebula Cluster (ONC) is the nearest region of massive star formation and thus a crucial testing ground for theoretical models. Of particular interest among the ONC's ∼1000 members are: θ1 Ori C, the most massive binary in the cluster with stars of masses 38 and 9 M☉; the Becklin-Neugebauer (BN) object, a 30 km/s runaway star of ∼8 M☉; and the Kleinmann-Low (KL) nebula protostar, a highly obscured, ∼15 M☉ object still accreting gas while also driving a powerful, apparently "explosive" outflow. The unusual behavior of BN and KL is much debated: How did BN acquire its high velocity? How is this related to massive star formation in the KL nebula? Here, we report the results of a systematic survey using ∼107 numerical experiments of gravitational interactions of the θ1C and BN stars. We show that dynamical ejection of BN from this triple system at its observed velocity leaves behind a binary with total energy and eccentricity matching those observed for θ1C. Five other observed properties of θ1C are also consistent with it having ejected BN and altogether we estimate that there is only a ≲ 10–5 probability that θ1C has these properties by chance. We conclude that BN was dynamically ejected from the θ1C system about 4500 years ago. BN then plowed through the KL massive star-forming core within the last 1000 years causing its recently enhanced accretion and outflow activity.