Pair Cascades in the Disk Environment of the Binary System PSR B1259-63/LS 2883

Abstract

PSR B1259-63/LS 2883 is a very high energy (VHE; $E>100$ GeV) γ-ray emitting binary consisting of a 48 ms pulsar orbiting around a Be star with a period of $\sim 3.4$ years. The Be star features a circumstellar disk which is inclined with respect to the orbit in such a way that the pulsar crosses it twice every orbit. The circumstellar disk provides an additional field of target photons which may contribute to inverse Compton scattering and γγ-absorption, leaving a characteristic imprint in the observed spectrum of the high energy emission. At GeV energies, the source was detected for the first time during the previous periastron passage which took place on December 15, 2010. The Fermi Large Area Telescope (LAT) reported a spectacular and unexpected γ-ray flare occurring around 30 days after periastron and lasting for about 7 weeks. In this paper, we study the signatures of Compton-supported, VHE γ-ray induced pair cascades in the circumstellar disc of the Be star and their possible contribution to the GeV flux. We show that cascade emission generated in the disk cannot be responsible for the GeV flare, but it might explain the GeV emission observed close to periastron. We also show that the γγ-absorption in the disk might explain the observed TeV light curve.

arXiv comment10 pages, 8 figures, accepted for publication in Journal of High Energy Astrophysics

References in corpus (14)

• Discovery of the Binary Pulsar PSR B1259-63 in Very-High-Energy Gamma Rays around Periastron with H.E.S.S
• Discovery of High-Energy Gamma-Ray Emission from the Binary System PSR B1259-63/LS 2883 Around Periastron with Fermi
• Gamma-ray absorption in massive X-ray binaries
• Discovery of GeV gamma-ray emission from PSR B1259-63/LS 2883
• Relativistic Doppler-boosted emission in gamma-ray binaries
• Modelling the light curves of PSR B1259-63/LS 2883-II.The effects of anisotropic pulsar wind and Doppler-boosting
• Multi-wavelength Observations of the Binary System PSR B1259-63/LS~2883 around the 2014 Periastron Passage
• Modeling high-energy light curves of the PSR B1259-63/LS 2883 binary based on 3-D SPH simulations
• Probing Pulsar Winds Using Inverse Compton Scattering
• New theoretical Mass-loss rates of O and B Stars
• H.E.S.S. Observations of the Binary System PSR B1259-63/LS 2883 around the 2010/2011 Periastron Passage
• Gamma-rays from cascades in close massive binaries containing energetic pulsars
• Gamma-rays from binary system with energetic pulsar and Be star with aspherical wind: PSR B1259-63/SS2883
• The Pair Production Spectrum from Photon-Photon Annihilation