Optical spectroscopy of PSR B1259-63/LS 2883 during the 2014 periastron passage with the Southern African Large Telescope

TL;DR

This study presents optical spectroscopic observations of the gamma-ray binary PSR B1259-63/LS 2883 during its 2014 periastron, revealing orbital variations and disc disruption consistent with pulsar interaction.

Contribution

First detailed optical spectroscopic monitoring of PSR B1259-63/LS 2883 during the 2014 periastron with SALT, showing orbital line variations and disc disruption evidence.

Findings

Orbital variation in Hα and He I lines around periastron.

Maximum line strength occurs ~13 days after periastron.

Weaker line strength compared to 2010 periastron.

Abstract

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 (SALT). The H{\alpha} and He I ({\lambda}6678) 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.