Non-thermal X-rays from Colliding Wind Shock Acceleration in the Massive Binary Eta Carinae

Abstract

Cosmic-ray acceleration has been a long-standing mystery and despite more than a century of study, we still do not have a complete census of acceleration mechanisms. The collision of strong stellar winds in massive binary systems creates powerful shocks, which have been expected to produce high-energy cosmic-rays through Fermi acceleration at the shock interface. The accelerated particles should collide with stellar photons or ambient material, producing non-thermal emission observable in X-rays and gamma-rays. The supermassive binary star eta Carinae drives the strongest colliding wind shock in the solar neighborhood. Observations with non-focusing high-energy observatories indicate a high energy source near eta Carinae, but have been unable to conclusively identify eta Carinae as the source because of their relatively poor angular resolution. Here we present the first direct focussing observations of the non-thermal source in the extremely hard X-ray band, which is found to be spatially coincident with the star within several arc-seconds. These observations show that the source of non-thermal X-rays varies with the orbital phase of the binary, and that the photon index of the emission is similar to that derived through analysis of the gamma-ray spectrum. This is conclusive evidence that the high-energy emission indeed originates from non-thermal particles accelerated at colliding wind shocks.

36 pages, 7 figures, 2 tables

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Cited by in corpus (30)

• Simulating the formation of $\eta$ Carinae's surrounding nebula through unstable triple evolution and stellar merger-induced eruption
• 3D simulations of clump formation in stellar wind collisions
• The Second AGILE Catalog of Gamma-Ray Sources
• NuSTAR measurement of the cosmic X-ray background in the 3-20 keV energy band
• Detection of very-high-energy γ-ray emission from the colliding wind binary η Car with H.E.S.S
• Modelling the interaction between relativistic and non-relativistic winds in binary pulsar systems: strong magnetization of the pulsar wind
• Particle acceleration and non-thermal emission in colliding-wind binary systems
• Gamma-ray and X-ray constraints on non-thermal processes in $\eta$ Carinae
• Colliding-wind binary systems: Diffusive shock acceleration and non-thermal emission
• Long-term soft and hard X-ray investigation of the colliding wind WN+O binary WR 25
• Eta Carinae with Fermi-LAT: Two full orbits and the third periastron
• CO, Water, and Possible Methanol in Eta Carinae Approaching Periastron
• The peculiar chemistry of the inner ejecta of Eta Carina
• Evidence for non-thermal X-ray emission from the double WR colliding-wind binary Apep
• Diffuse $\gamma$-ray emission around the massive star forming region of Carina Nebula Complex
• X-ray emission of massive stars and their winds
• Investigation of the WR 11 field at decimeter wavelengths
• Radio emission from colliding outflows in high-mass X-ray binaries with strongly magnetized neutron stars
• Inverse Compton cooling of thermal plasma in colliding-wind binaries
• The high-energy emission from HD~93129A near periastron
• $\eta$ Carinae: high angular resolution continuum, H30$\alpha$ and He30$\alpha$ ALMA images
• Search for non-thermal X-ray emission in the colliding wind binary Cyg OB2 #8A
• On the Energy Dependence of Galactic Cosmic Ray Anisotropies in the Very Local Interstellar Medium
• Probing cosmic ray escape from η Carinae
• Chandra X-ray Measurement of Heavy Element Abundances of Wolf-Rayet Stars in the Galactic Center
• Detection of very-high-energy gamma-ray emission from Eta Carinae during its 2020 periastron passage
• Exploring the MeV Sky with a Combined Coded Mask and Compton Telescope: The Galactic Explorer with a Coded Aperture Mask Compton Telescope (GECCO)
• Radio study of the colliding wind binary HD93129A near periastron and its surroundings
• Revealing the accelerating wind in the inner region of the colliding-wind binary WR 112
• Limits on the non-thermal emission of the WR-WR system Apep