Bispectrum speckle interferometry of the Orion Trapezium stars: detection of a close (33 mas) companion of Theta(1) Ori C

We present bispectrum speckle interferometry observations with the SAO 6 m telescope of the four brightest stars in the Orion Trapezium. Diffraction-l imited images with an unprecedented resolution lambda/D of 57 mas and 76 ma s were obtained in the H- and K-band, respectively. The H and K images of T heta(1)Ori C (the star responsible for the proplyds) show for the first tim e that Theta(1)Ori C is a close binary with a separation of only similar to 33 mas (H-band observation). The sub-arcsecond companions of Theta(1)Ori A and Theta(1)Ori B reported by Petr et al. (1998) are confirmed. We use the magnitudes and colors of the companions to derive information about their stellar properties from the HR-diagram. In addition we briefly discuss the multiplicity of the Trapezium stars. Considering both, the visual and the s pectroscopic companions of the 4 Trapezium stars, there are at least 7 comp anions, i.e. at least 1.75 companions per primary on average. This number i s clearly higher than that found for the low-mass stars in the Orion Nebula cluster as well as in the field population. This suggests that a different mechanism is at work in the formation of high-mass multiple systems in the dense Trapezium cluster than for low-mass stars.