Orbital motion of the massive multiple stars in the Orion Trapezium

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

Astronomy and Astrophysics, 402, 267 (2003)


We present bispectrum speckle interferometry of the multiple Orion Trapezium stars θ1Ori A, θ1Ori B, and θ1OriC 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 λ/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 θ1Ori A1–2 (mean separation ρ ∼ 220 mas, change in position angle ΔPA = 6°), θ1Ori B2–3 (ρ ∼ 205 mas, ΔPA = 8°), and θ1Ori C1–2 (ρ ∼ 37 mas, ΔPA = 18°). In our K-band image of θ1OriB 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 θ1Ori C2 and θ1Ori B2 show clear evidence of near-infrared excess in the color-color diagram. The companions θ1Ori A2 and θ1Ori B3 show much stronger extinction than their primary stars, providing evidence of the presence of circumstellar material around the companions.

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