The eclipsing, double-lined, Of supergiant binary Cygnus OB2-B17

¹ Faulkes Telescope Project, School of Physics and Astronomy, Cardiff University, Cardiff, CF24 3AA, UK e-mail: vanessa.stroud@faulkes-telescope.com
² Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
³ Division of Earth, Space and Environment, University of Glamorgan, Pontypridd, CF37 1DL, UK
⁴ Departamento de Física, Ingeniería de Sistemas y Teoría de la Señal, Universidad de Alicante, Apdo. 99, 03080 Alicante, Spain

Received: 20 March 2009
Accepted: 15 December 2009

Abstract

Context. Massive, eclipsing, double-lined, spectroscopic binaries are not common but are necessary to understand the evolution of massive stars as they are the only direct way to determine stellar masses. They are also the progenitors of energetic phenomena such as X-ray binaries and γ-ray bursts.

Aims. We present a photometric and spectroscopic analysis of the candidate binary system Cyg OB2-B17 to show that it is indeed a massive evolved binary.

Methods. We utilise V band and white-light photometry to obtain a light curve and period of the system, and spectra at different resolutions to calculate preliminary orbital parameters and spectral classes for the components.

Results. Our results suggest that B17 is an eclipsing, double-lined, spectroscopic binary with a period of days, with two massive evolved components with preliminary classifications of O7 and O9 supergiants. The radial velocity and light curves are consistent with a massive binary containing components with similar luminosities, and in turn with the preliminary spectral types and age of the association.