Orbital motion of the massive multiple stars in the Orion Trapezium

We present bispectrum speckle interferometry of the multiple Orion Trapezium stars theta(1) Ori A, theta(1) Ori B, and theta(1) OriC 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) Ori A1-2 (mean separation rho similar to 220 mas, change in position angle DeltaPA = 6degrees), theta(1)Ori B2-3 (rho similar to 205 mas, DeltaPA = 8degrees), and theta(1) Ori C1-2 (rho similar to 37 mas, DeltaPA = 18degrees). In our K-band image of theta(1) OriB 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.