Optical spectroscopy of the microquasar GRS 1758−258: a possible intermediate mass system? Josep Martí, Pedro L. Luque-Escamilla and Álvaro J. Muñoz-Arjonilla A&A, 596 (2016) A46 Published online: 28 November 2016 DOI: 10.1051/0004-6361/201629630