Astron. Astrophys. 347, L15-L18 (1999)

Letter to the Editor

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

Gerd Weigelt ¹, Yuri Balega ², Thomas Preibisch ¹, Dieter Schertl ¹, Markus Schöller ³ and Hans Zinnecker <sup>4

1</sup> Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-95121 Bonn, Germany
² Special Astrophysical Observatory, Nizhnij Arkhyz, Zelenchuk region, Karachai-Cherkesia, 357147, Russia
³ European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany
⁴ Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany

Received 28 April 1999 / Accepted 5 June 1999

Abstract

We present bispectrum speckle interferometry observations with the SAO 6 m telescope of the four brightest stars in the Orion Trapezium. Diffraction-limited images with an unprecedented resolution of 57 mas and 76 mas were obtained in the H- and K-band, respectively. The H and K images of C (the star responsible for the proplyds) show for the first time that C is a close binary with a separation of only mas (H-band observation). The sub-arcsecond companions of A and 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 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.

Key words: techniques: interferometric stars: individual: 1 Ori C; 1 Ori A; 1 Ori B stars: pre-main sequence stars: binaries: close

* Based on data collected at the SAO 6 m telescope in Russia.

Send offprint requests to: weigelt@mpifr-bonn.mpg.de

© European Southern Observatory (ESO) 1999

Online publication: June 30, 1999

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