Tango, W. J. and Davis, J. and Ireland, M. J. and Aerts, C. and Uyterhoeven, K. and Jacob, A. P. and Mendez, A. and North, J. R. and Seneta, E. B. and Tuthill, P. G. (2006) Orbital elements, masses and distance of λ Scorpii A and B determined with the Sydney University Stellar Interferometer and high-resolution spectroscopy. Monthly Notices of the Royal Astronomical Society, 370 (2). pp. 884-890. ISSN 0035-8711 http://resolver.caltech.edu/CaltechAUTHORS:20110804-111905039
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The triple system HD 158926 (λ Sco) has been observed interferometrically with the Sydney University Stellar Interferometer, and the elements of the wide orbit have been determined. These are significantly more accurate than the previous elements found spectroscopically. The inclination of the wide orbit is consistent with the inclination previously found for the orbit of the close companion. The wide orbit also has low eccentricity, suggesting that the three stars were formed at the same time. The brightness ratio between the two B stars was also measured at λ= 442 and 700 nm. The brightness ratio and colour index are consistent with the previous classification of λ Sco A as B1.5 and λ Sco B as B2. Evolutionary models show that the two stars lie on the main sequence. Since they have the same age and luminosity class (IV), the mass–luminosity relation can be used to determine the mass ratio of the two stars: M_B/M_A= 0.76 ± 0.04. The spectroscopic data have been reanalyzed using the interferometric values for P, T, e and ω, leading to revised values for a_1 sin i and the mass function. The individual masses can be found from the mass ratio, the mass function, spectrum synthesis and the requirement that the age of both components must be the same: M_A= 10.4 ± 1.3 and M_B= 8.1 ± 1.0 M_⊙. The masses, angular semimajor axis and the period of the system can be used to determine the dynamical parallax. We find the distance to λ Sco to be 112 ± 5 pc, which is approximately a factor of 2 closer than the Hipparcos value of 216 ± 42 pc.
|Additional Information:||© 2006 The Authors. Journal compilation © 2006 RAS. Accepted 2006 May 3. Received 2006 April 21; in original form 2005 December 10. Article first published online: 20 Jun 2006. This research has been carried out as a part of the SUSI project, jointly funded by the University of Sydney and the Australian Research Council. MJI acknowledges the support provided by an Australian Postgraduate Award; APJ acknowledges the support of a Denison Postgraduate Award from the School of Physics and JRN acknowledges the support of a University of Sydney Postgraduate Award. CA and KU are supported by the Fund for Scientific Research of Flanders (FWO) under grant G.0332.06 and by the Research Council of the University of Leuven under grant GOA/2003/04.|
|Subject Keywords:||techniques: interferometric; binaries: spectroscopic; binaries: visual; stars: fundamental parameters|
|Official Citation:||Orbital elements, masses and distance of λ Scorpii A and B determined with the Sydney University Stellar Interferometer and high-resolution spectroscopy (pages 884–890) W. J. Tango, J. Davis, M. J. Ireland, C. Aerts, K. Uytterhoeven, A. P. Jacob, A. Mendez, J. R. North, E. B. Seneta and P. G. Tuthill Article first published online: 20 JUN 2006 | DOI: 10.1111/j.1365-2966.2006.10526.x|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||04 Aug 2011 20:13|
|Last Modified:||04 Aug 2011 20:13|
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