Dieter Schertl, Yuri Y. Balega, Thomas Preibisch, Gerd Weigelt

Orbital motion of the massive multiple stars in the Orion Trapezium

Astronomy and Astrophysics, 402, 267-275 (2003)

We present bispectrum speckle interferometry of the multiple Orion Trapezium stars theta^1 Ori A, B, and C obtained with the SAO 6m 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 Ori A1-2 (mean separation rho ~ 220 mas, change in position angle Delta P.A. = 6degr), theta^1 Ori B2-3 (rho ~ 205 mas, Delta P.A. = 8degr), and theta^1 Ori C1-2 (rho ~ 37 mas, Delta P.A. = 18degr). In our K-band image of theta^1 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 Ori C2 and theta^1 Ori B2 show clear evidence of near-infrared excess in the color-color diagram. The companions theta^1 Ori A2 and theta^1 Ori B3 show much stronger extinction than their primary stars, providing evidence of the presence of circumstellar material around the companions.

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