On the origin of γ-ray emission in η Carina

Abstract

η Car is the only colliding-wind binary for which high-energy γ rays are detected. Although the physical conditions in the shock region change on timescales of hours to days, the variability seen at GeV energies is weak and on significantly longer timescales. The γ-ray spectrum exhibits two features that can be interpreted as emission from the shocks on either side of the contact discontinuity. Here we report on the first time-dependent modelling of the non-thermal emission in η Car. We find that emission from primary electrons is likely not responsible for the γ-ray emission, but accelerated protons interacting with the dense wind material can explain the observations. In our model, efficient acceleration is required at both shocks, with the primary side acting as a hadron calorimeter, whilst on the companion side acceleration is limited by the flow time out of the system, resulting in changing acceleration conditions. The system therefore represents a unique laboratory for the exploration of hadronic particle acceleration in non-relativistic shocks.

5 pages, 4 figures, 1 table, accepted for publication in MNRAS Letters

References in corpus (8)

• Fermi Large Area Telescope Bright Gamma-ray Source List
• Detection of Gamma-ray Emission from the Eta-Carinae Region
• Non-thermal emission processes in massive binaries
• A 3D dynamical model of the colliding winds in binary systems
• Inverse Compton Scenarios for the TeV Gamma-Ray Emission of the Galactic Centre
• X-Rays From Massive OB Stars: Thermal Emission From Radiative Shocks
• Gamma-ray follow-up studies on Eta Carinae
• Hard X-ray identification of Eta Carinae and steadiness close to periastron

Cited by in corpus (3)

• Non-thermal X-rays from Colliding Wind Shock Acceleration in the Massive Binary Eta Carinae
• Overview of non-transient gamma-ray binaries and prospects for the Cherenkov Telescope Array
• A lepto-hadronic model of gamma rays from the Eta Carinae and prospects for neutrino telescopes