Detection of nitrogen gas in the β Pictoris circumstellar disc P. A. Wilson, R. Kerr, A. Lecavelier des Etangs, V. Bourrier, A. Vidal-Madjar, F. Kiefer and I. A. G. Snellen A&A, 621 (2019) A121 Published online: 16 January 2019 DOI: 10.1051/0004-6361/201834346