BISPECTRUM SPECKLE INTERFEROMETRY OF THE ORION TRAPEZIUM STARS : DETECTIONOF A CLOSE (33 MAS) COMPANION OF THETA 1ORI C

We present bispectrum speckle interferometry ob- servations with the SAO 6 m telescope of the four brightest stars in the Orion Trapezium. Diffraction-limited images with an unprecedented resolution =D of 57 mas and 76 mas were obtained in the H- and K-band, respectively. The H and K im- ages of 1 Ori C (the star responsible for the proplyds) show for the first time that 1 Ori C is a close binary with a separation of only 33 mas (H-band observation). The sub-arcsecond com- panions of 1 Ori A and 1 Ori B reported by Petr et al. (1998) are confirmed. We use the magnitudes and colors of the com- panions to derive information about their stellar properties from the HR-diagram. In addition we briefly discuss the multiplic- ity of the Trapezium stars. Considering both, the visual and the spectroscopic companions of the 4 Trapezium stars, there are at least 7 companions, i.e. at least 1.75 companions per primary on average. This number is 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.