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Astron. Astrophys. 327, 1094-1106

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V 3903 Sagittarii: a massive main-sequence (O7V+O9V) detached eclipsing binary*

L.P.R. Vaz1,3, N.C.S. Cunha1, E.F. Vieira2,1, and M.L.M. Myrrha1

1Departamento de Física, ICEx, UFMG, Caixa Postal 702, 30.161-970 Belo Horizonte MG, Brazil
2European Space Agency-ESA, Villafranca del Castillo, Apdo. 50727, E-28080 Madrid, Spain
3Department of Astronomy, University of Wisconsin, Madison, Wisconsin 53706, USA

Received 22 May 1997 / Accepted 11 July 1997


We present for the first time an analysis based on uvby light curves, H$\beta$ indices and on new spectroscopic data of the massive detached double-lined O-type eclipsing binary V 3903 Sgr. The uvby light curves are analysed with the WINK (initial solutions) and the Wilson-Devinney (WD, final solution) programs. Both codes were used in their extended versions, with stellar atmospheres and taking into account the geometric distortions and photometric effects caused by proximity of the components.

The spectroscopic CCD observations were analysed with the harmonic ``Wilsing-Russell'' and the ``Lehman-Filhes'' methods. We conclude that V 3903 Sgr is one of the rare O-type detached systems where both components are still on the initial phases of the main sequence, with an age of either 1.6$\times$106 yrs or $2.5\times$106 yrs (depending on the evolutionary model adopted) at a distance of $\approx$1500 pc, the same as for the Lagoon Nebula (Messier8) complex, of which the system is probably a member. We determine the absolute dimensions: MA=27.27$\pm$0.55, RA=8.088$\pm$0.086, MB=19.01$\pm$0.44 and RB=6.125$\pm$0.060 (solar units). There is no evidence of mass transfer and the system is detached. The orbit is circular, and both components show synchronous rotation, despite their early evolutionary stage. The absolute dimensions determined should be representative for normal single stars. Amongst the massive systems (M>17${\rm M_{\odot}}$) with precise absolute dimensions (errors <2%), V 3903 Sgr is that with the most massive primary, with the largest mass difference between the components, and it is the youngest one.

Key words: binaries: eclipsing - stars: individual: V 3903 Sgr; early type; fundamental parameters

*Based on data collected with the 60cm and 1.6m telescopes at the Pico dos Dias Observatory, National Laboratory of Astrophysics, LNA-CNPq, Brasópolis, MG, Brazil and with the Danish 50cm telescope (SAT) at the European Southern Observatory (ESO), La Silla, Chile

Send offprint requests to: L.P.R. Vaz at address 1 or at lpvfisica.ufmg.br

© European Southern Observatory (ESO) 1997

Online publication: October 20, 1997
Last change: April 6, 1998