Optical spectroscopy of the Be/X-ray binary V850 Centauri/GX 304-1 during faint X-ray periodical activityC. Malacaria, W. Kollatschny, E. Whelan, A. Santangelo, D. Klochkov, V. McBride and L. DucciA&A, 603 (2017) A24DOI: https://doi.org/10.1051/0004-6361/201730538