2016MNRAS.455.3674V

The gamma-ray binary system PSR B1259-63/LS 2883 went through periastron in May 2014. We report on the optical spectroscopic monitoring of the system from 33 d before to 78 d after periastron, undertaken with the Southern African Large Telescope. The Hα and Hei (λ6678) lines exhibit an orbital variation around periastron, with the line strengths reaching a maximum ∼ 13 d after periastron. The line strength is weaker than observed around the previous periastron in 2010. There is also a marked change in the line strength and asymmetry around the first disc crossing. These observations are consistent with the disruption of the circumstellar disc around periastron due to the interaction with the pulsar.