Orbital motion of the massive multiple stars in the Orion Trapezium

Free access article

Issue		A&A Volume 402, Number 1, April IV 2003


Page(s)		267 - 275
Section		Stellar atmospheres
DOI		10.1051/0004-6361:20030225

A&A 402, 267-275 (2003)
DOI: 10.1051/0004-6361:20030225

Orbital motion of the massive multiple stars in the Orion Trapezium

D. Schertl¹, Y. Y. Balega², Th. Preibisch¹ and G. Weigelt¹

¹ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
² Special Astrophysical Observatory, Nizhnij Arkhyz, Zelenchuk region, Karachai-Cherkesia, 357147, Russia

(Received 12 August 2002 / Accepted 6 February 2003 )

Abstract
We present bispectrum speckle interferometry of the multiple Orion Trapezium stars $\theta^1{\rm Ori}$ A, $\theta^1{\rm Ori}$ B, and $\theta^1{\rm Ori}$ C obtained with the SAO 6 m telescope in Russia over a period of 5.5 years (epochs 1995-2001). Our diffraction-limited images have a resolution $\lambda/D$ of 42 mas ( J-band), 57 mas ( H-band) and 76 mas ( K-band). We clearly detect motion of the companions relative to their primary stars in the systems $\theta^1{\rm Ori}$ A1-2 (mean separation $\rho\sim 220$ mas, change in position angle $\Delta {\rm PA} = 6\degr$ ), $\theta^1{\rm Ori}$ B2-3 ( $\rho\sim 205$ mas, $\Delta {\rm PA} = 8\degr$ ), and $\theta^1{\rm Ori}$ C1-2 ( $\rho\sim 37$ mas, $\Delta {\rm PA} = 18\degr$ ). In our K-band image of $\theta^1{\rm Ori}$ B we resolve a fourth visual component, confirming its discovery by Simon et al. (1999). We determine the J, H, and K magnitudes of the system components and estimate the stellar masses of the companions in the HR-diagram. The companions $\theta^1{\rm Ori}$ C2 and $\theta^1{\rm Ori}$ B2 show clear evidence of near-infrared excess in the color-color diagram. The companions $\theta^1{\rm Ori}$ A2 and $\theta^1{\rm Ori}$ B3 show much stronger extinction than their primary stars, providing evidence of the presence of circumstellar material around the companions.

Key words: techniques: interferometric -- stars: individual: $\theta^1{\rm Ori}$ C, $\theta^1{\rm Ori}$ A, $\theta^1{\rm Ori}$ B -- stars: binaries: general -- stars: pre-main sequence

Offprint request: Th. Preibisch, preib@mpifr-bonn.mpg.de

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