Orbits, Distance, and Stellar Masses of the Massive Triple Star Sigma Orionis
ten Brummelaar, T
American Astronomical Society / IOP Publishing
© 2016. The American Astronomical Society. All rights reserved.
We present interferometric observations of the σ Orionis triple system using the CHARA Array, NPOI, and VLTI. Using these measurements, we spatially resolve the orbit of the close spectroscopic binary (Aa,Ab) for the first time and present a revised orbit for the wide pair (A,B). Combining the visual orbits with previously published radial velocity measurements and new radial velocities measured at CTIO, we derive dynamical masses for the three massive stars in the system of MAa = 16.99 ± 0.20 M, MAb = 12.81 ± 0.18 M, and MB = 11.5 ± 1.2 M. The inner and outer orbits in the triple are not coplanar, with a relative inclination of 120–127. The orbital parallax provides a precise distance of 387.5 ± 1.3 pc to the system. This is a significant improvement over previous estimates of the distance to the young σ Orionis cluster.
We thank Deane Peterson for initially proposing to observe σ Orionis with NPOI, and acknowledge his and Tom Bolton's support of the project during the initial phase. We appreciate P. J. Goldfinger, Nic Scott, and Norm Vargas for providing operational support during the CHARA observations. We are grateful to Ming Zhao for collecting an early set of CHARA data on σ Orionis before the photometric channels were installed in MIRC. We thank Jim Benson and the NPOI observational support staff whose efforts made the observations possible. We appreciate Floor van Leeuwen for a helpful discussion on the parallaxes of multiple stars observed by the Hipparcos mission. We thank the referee for providing feedback to improve the manuscript. This work is based on observations obtained with the Georgia State University Center for High Angular Resolution Astronomy Array at Mount Wilson Observatory. The CHARA Array is supported by the National Science Foundation (NSF) under grant No. AST-1211929. G.H.S. and D.R.G. acknowledge support from NSF Grant AST-1411654. Institutional support has been provided from the GSU College of Arts and Sciences and the GSU Office of the Vice President for Research and Economic Development. The Navy Precision Optical Interferometer is a joint project of the Naval Research Laboratory and the US Naval Observatory, in cooperation with Lowell Observatory and is funded by the Office of Naval Research and the Oceanographer of the Navy. F.M.W. thanks Dennis Assanis, Provost of Stony Brook University, for enabling access to Chiron spectrograph, operated by the SMARTS consortium, through a Research Support grant. F.B. acknowledges funding from NSF-AST grants 1445935 and 1616483. S.K. acknowledges support from a European Research Council Starting Grant (Grant Agreement No. 639889). This research has made use of the SIMBAD astronomical literature database, operated at CDS, Strasbourg, France and the Washington Double Star Catalog maintained at the U.S. Naval Observatory.
This is the author accepted manuscript. The final version is available from American Astronomical Society via the DOI in this record.
Vol. 152 (6), article 213