IngentaConnect N-body simulations of stars escaping from the Orion nebula

Authors: Gualandris A.; Portegies Zwart S.; Eggleton P.P.¹

Source: Monthly Notices of the Royal Astronomical Society, Volume 350, Number 2, May 2004 , pp. 615-626(12)

Abstract:

We study the dynamical interaction in which the two single runaway stars, AE Aurigæ and

Columbæ, and the binary iota

Orionis acquired their unusually high space velocity. The two single runaways move in almost opposite directions with a velocity greater than 100 km s^-1 away from the Trapezium cluster. The star iota

Orionis is an eccentric (e sime

0.8) binary moving with a velocity of about 10 km s^-1 at almost right angles with respect to the two single stars. The kinematic properties of the system suggest that a strong dynamical encounter occurred in the Trapezium cluster about 2.5 Myr ago. Curiously enough, the two binary components have similar spectral type but very different masses, indicating that their ages must be quite different. This observation leads to the hypothesis that an exchange interaction occurred in which an older star was swapped into the original iota

Orionis binary. We test this hypothesis by a combination of numerical and theoretical techniques, using N-body simulations to constrain the dynamical encounter, binary evolution calculations to constrain the high orbital eccentricity of iota

Orionis and stellar evolution calculations to constrain the age discrepancy of the two binary components. We find that an encounter between two low eccentricity (0.4 lsim

0.6) binaries with comparable binding energy, leading to an exchange and the ionization of the wider binary, provides a reasonable solution to this problem.

Keywords: methods: N-body simulations; binaries: spectroscopic; stars: individual: HD 34078; stars: individual: HD 37043; stars: individual: HD 38666

Document Type: Research article

DOI: 10.1111/j.1365-2966.2004.07673.x

Affiliations: 1: Lawrence Livermore National Laboratory, Livermore, CA 94550-9234, USA

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