The puzzling properties of the magnetic O star Tr16-22 Yaël Nazé, Rodolfo Barbá, Stefano Bagnulo, Nidia Morrell, Roberto Gamen, Véronique Petit and Coralie Neiner A&A, 596 (2016) A44 Published online: 28 November 2016 DOI: 10.1051/0004-6361/201629320