Portal de Periódicos da CAPES

Multiple star systems in the Orion nebula

2018; EDP Sciences; Volume: 620; Linguagem: Inglês

10.1051/0004-6361/201833575

1432-0746

Martina Karl, O. Pfuhl, Frank Eisenhauer, R. Genzel, Rebekka Grellmann, M. Habibi, Roberto Abuter, Matteo Accardo, A. Amorim, Narsireddy Anugu, Gerardo Ávila, M. Benisty, Jean-Philippe Berger, Nicolas Blind, Henri Bonnet, P. Bourget, W. Brandner, R. Brast, A. Buron, A. Caratti o Garatti, F. Chapron, Yann Clénet, C. Collin, Vincent Coudé du Foresto, W. J. de Wit, P. T. de Zeeuw, C. Deen, F. Delplancke-Ströbele, R. Dembet, F. Dérie, Jason Dexter, G. Duvert, Monica Ebert, A. Eckart, Michael Esselborn, P. Fédou, Gert Finger, P. García, C. E. García Dabó, R. García López, F. Gao, É. Gendron, S. Gillessen, Frédéric Gonté, Paulo Gordo, U. Grözinger, Patricia Guajardo, Sylvain Guieu, Pierre Haguenauer, O. Hans, X. Haubois, M. Haug, F. Haußmann, Thomas Henning, S. Hippler, M. Horrobin, Armin Huber, Z. Hubert, N. Hubin, Gerd Jakob, L. Jochum, L. Jocou, A. Kaufer, S. Kellner, Sarah Kendrew, L. Kern, P. Kervella, M. Kiekebusch, Ralf Klein, R. Köhler, J. Kolb, Martin Kulas, S. Lacour, V. Lapeyrère, B. Lazareff, J.-B. Le Bouquin, Pierre Léna, R. Lenzen, Samuel Lévêque, Chien-Cheng Lin, M. Lippa, Y. Magnard, Leander Mehrgan, A. Mérand, Thibaut Moulin, E. Müller, Friedrich Müller, Udo Neumann, Sylvain Oberti, Thomas Ott, Laurent Pallanca, J. Panduro, Luca Pasquini, T. Paumard, Isabelle Percheron, K. Perraut, G. Perrin, A. Pflüger, Thanh Phan Duc, P. M. Plewa, Dan Popovic, S. Rabien, Andrés Ramírez, J. R. Ramos, Christian Rau, Miguel Riquelme, G. Rodríguez-Coira, Ralf-Rainer Rohloff, A. Jiménez-Rosales, G. Rousset, J. Sánchez-Bermúdez, Silvia Scheithauer, Markus Schöller, Nicolas Schuhler, J. Spyromilio, O. Straub, C. Straubmeier, Eckhard Sturm, Marcos Suárez, K. R. W. Tristram, N. Ventura, F. Vincent, Idel Waisberg, I. Wank, F. Widmann, E. Wieprecht, Michael Wiest, E. Wiezorrek, M. Wittkowski, J. Woillez, B. Wolff, Ş. Yazıcı, D. Ziegler, G. Zins,

Astro and Planetary Science

This work presents an interferometric study of the massive-binary fraction in the Orion Trapezium Cluster with the recently comissioned GRAVITY instrument. We observe a total of 16 stars of mainly OB spectral type. We find three previously unknown companions for $\theta ^1$ Ori B, $\theta ^2$ Ori B, and $\theta ^2$ Ori C. We determine a separation for the previously suspected companion of NU Ori. We confirm four companions for $\theta ^1$ Ori A, $\theta ^1$ Ori C, $\theta ^1$ Ori D, and $\theta ^2$ Ori A, all with substantially improved astrometry and photometric mass estimates. We refine the orbit of the eccentric high-mass binary $\theta ^1$ Ori C and we are able to derive a new orbit for $\theta ^1$ Ori D. We find a system mass of 21.7 $M_{\odot}$ and a period of $53$ days. Together with other previously detected companions seen in spectroscopy or direct imaging, eleven of the 16 high-mass stars are multiple systems. We obtain a total number of 22 companions with separations up to 600 AU. The companion fraction of the early B and O stars in our sample is about 2, significantly higher than in earlier studies of mostly OB associations. The separation distribution hints towards a bimodality. Such a bimodality has been previously found in A stars, but rarely in OB binaries, which up to this point have been assumed to be mostly compact with a tail of wider companions. We also do not find a substantial population of equal-mass binaries. The observed distribution of mass ratios declines steeply with mass, and like the direct star counts, indicates that our companions follow a standard power law initial mass function. Again, this is in contrast to earlier findings of flat mass ratio distributions in OB associations. We exclude collision as a dominant formation mechanism but find no clear preference for core accretion or competitive accretion.