High-energy observations of PSR B1259-63/LS 2883 through the 2014 periastron passage: connecting X-rays to the GeV flare

TL;DR

This study analyzes multi-wavelength observations of PSR B1259-63/LS 2883 during the 2014 periastron, revealing the repetitive nature of GeV flares and their connection to X-ray emissions, suggesting synchrotron radiation from shocked pulsar wind.

Contribution

It provides the first evidence of contemporaneous X-ray and GeV flares during the 2014 periastron, linking high-energy emissions to synchrotron radiation from the pulsar wind.

Findings

Repetitive GeV flares observed at similar orbital phases as in 2011.

Concurrent X-ray flux variations during GeV flares.

Broadband spectra consistent with synchrotron radiation from shocked pulsar wind.

Abstract

The binary system PSR B1259-63/LS 2883 is well sampled in radio, X-rays, and TeV gamma-rays, and shows orbital phase-dependent variability in these frequencies. The first detection of GeV gamma-rays from the system was made around the 2010 periastron passage. In this Letter, we present an analysis of X-ray and gamma-ray data obtained by the Swift/XRT, NuSTAR/FPM, and Fermi/LAT, through the recent periastron passage which occurred on 2014 May 4. While PSR B1259-63/LS 2883 was not detected by the LAT before and during this passage, we show that the GeV flares occurred at a similar orbital phase as in early 2011, thus establishing the repetitive nature of the post-periastron GeV flares. Multiple flares each lasting for a few days have been observed and short-term variability is seen as well. We also found X-ray flux variation contemporaneous with the GeV flare for the first time. A strong evidence of the keV-to-GeV connection came from the broadband high-energy spectra, which we interpret as synchrotron radiation from the shocked pulsar wind.