Simulating three-dimensional nonthermal high-energy photon emission in colliding-wind binaries

Abstract

Massive stars in binary systems have long been regarded as potential sources of high-energy gamma rays.The emission is principally thought to arise in the region where the stellar winds collide and accelerate relativistic particles which ubsequently emit gamma rays. On the basis of a three-dimensional distribution function of high-energy particles in the wind collision region - as obtained by a numerical hydrodynamics and particle transport model - we present the computation of the three-dimensional nonthermal photon emission for a given line of sight. Anisotropic inverse Compton emission is modelled using the target radiation field of both stars. Photons from relativistic bremsstrahlung and neutral pion decay are computed on the basis of local wind plasma densities. We also consider photon photon opacity effects due to the dense radiation fields of the stars. Results are shown for different stellar separations of a given binary system comprising of a B star and a Wolf-Rayet star. The influence of orbital orientation with respect to the line of sight is also studied by using different orbital viewing angles. For the chosen electron-proton injection ratio of 0.01, we present the ensuing photon emission in terms of two-dimensional projections maps, spectral energy distributions and integrated photon flux values in various energy bands. Here, we find a transition from hadron-dominated to lepton-dominated high-energy emission with increasing stellar separations. In addition, we confirm findings from previous analytic modeling that the spectral energy distribution varies significantly with orbital orientation.

25 pages, 13 figures, accepted for publication in The Astrophysical Journal

References in corpus (1)

• Gamma-ray follow-up studies on Eta Carinae

Cited by in corpus (13)

• The first full orbit of Eta Carinae seen by Fermi
• Modelling the interaction between relativistic and non-relativistic winds in binary pulsar systems: strong magnetization of the pulsar wind
• 3D magneto-hydrodynamic models of non-thermal photon emission in the binary system ${\gamma }^2$ Velorum
• Cosmic rays in astrospheres
• Supercritical colliding wind binaries
• Colliding-wind Binaries with strong magnetic fields
• Eta Carinae with Fermi-LAT: Two full orbits and the third periastron
• Megahertz emission of massive early-type stars in the Cygnus region
• Variable millimetre radiation from the colliding-wind binary Cyg OB2 #8A
• Colliding-Wind Binaries as a Source of TeV Cosmic Rays
• Gamma Rays from colliding winds in massive binaries. Status and prospects
• MHD Models of Gamma-ray Emission in WR 11
• Combined Magnetohydrodynamic- Monte Carlo Simulations of Proton Acceleration in Colliding Wind Binaries