26-10-2011 13:30 hs.
Orion BN/KL: A laboratory for high-mass star formation
Dr. Ciriaco Goddi – Garching, ESO
The details of how massive stars form are poorly known. Orion BN/KL is the closest known region with ongoing massive star formation, and hence offers unique chances for a detailed study. Despite being considered an archetype, it is still poorly understood. I will review recent work which has resolved long-standing debates on this enigmatic region, focusing on three different aspects.
First, I will report on a monitoring of different SiO maser transitions at 7mm over several years with the VLBA and VLA toward the massive radio source-I, which provided us with the 3D dynamics of circumstellar gas and enabled for the first time to resolve outflow at/near launch (<100 AU) and collimation (100-1000 AU) and demonstrate ongoing disk-mediated accretion in a high-mass protostar.
Second, I will describe a reconstruction of the recent dynamical history of the region based on proper motions of radio sources, which show that protostars Source I and BN (4000 AU apart) must have experienced a close passage [O(50 AU)] 500 years ago. N-body numerical simulations show that the dynamical interaction between a binary of 20 Solar mass (Source I) and a single star of 10 solar mass (BN) may lead to ejection of both and binary hardening, while preserving the original circumbinary disk around Source I (and possibly triggering ejection of the explosive BN/KL flow).
Finally, I will briefly present the hypothesis of external heating of the eponymous Orion Hot Core by shocks produced by Source-I?s outflow, based on recent observations of high-energy transitions of ammonia.
A better understanding of Orion BN/KL allows to advance our understanding of high-mass star formation.