Testing the theory of colliding winds: the periastron passage of 9 Sagittarii - I. X-ray and optical spectroscopyG. Rauw, R. Blomme, Y. Nazé, M. Spano, L. Mahy, E. Gosset, D. Volpi, H. van Winckel, G. Raskin and C. WaelkensA&A, 589 (2016) A121DOI: https://doi.org/10.1051/0004-6361/201526871
