Interstellar oxygen along the line of sight of Cygnus X-2 I. Psaradaki, E. Costantini, M. Mehdipour, D. Rogantini, C. P. de Vries, F. de Groot, H. Mutschke, S. Trasobares, L. B. F. M. Waters and S. T. Zeegers A&A, 642 (2020) A208 Published online: 22 October 2020 DOI: 10.1051/0004-6361/202038749