Multi-wavelength Observations of the Binary System PSR B1259-63/LS~2883 around the 2014 Periastron Passage

TL;DR

This study presents multi-wavelength observations of PSR B1259-63 during its 2014 periastron, revealing a stable GeV flare linked to stellar disk disruption and changes in X-ray spectra explained by synchrotron cooling.

Contribution

It provides new insights into the correlation between GeV flares and stellar disk disruption in a high-mass gamma-ray binary during periastron.

Findings

Stable GeV flare coincides with Hα disk decay.

X-ray spectral changes align with synchrotron cooling.

Flares are associated with relativistic electron injection.

Abstract

We report on the results of the extensive multi-wavelength campaign from optical to GeV gamma-rays of the 2014 periastron passage of PSR B1259-63, which is a unique high-mass gamma-ray emitting binary system with a young pulsar companion. Observations demonstrate the stable nature of the post-periastron GeV flare and prove the coincidence of the flare with the start of rapid decay of the H$\alpha$ equivalent width, usually interpreted as a disruption of the Be stellar disk. Intensive X-ray observations reveal changes in the X-ray spectral behaviour happening at the moment of the GeV flare. We demonstrate that these changes can be naturally explained as a result of synchrotron cooling of monoenergetic relativistic electrons injected into the system during the GeV flare.