Hard X-ray emission from Eta Carinae

Abstract

Context : If relativistic particle acceleration takes place in colliding-wind binaries, hard X-rays and gamma-rays are expected through inverse Compton emission, but to date these have never been unambiguously detected. Aims : To detect this emission, observations of Eta Carinae were performed with INTEGRAL, leveraging its high spatial resolution. Methods : Deep hard X-ray images of the region of Eta Car were constructed in several energy bands. Results : The hard X-ray emission previously detected by BeppoSax around Eta Car originates from at least 3 different point sources. The emission of Eta Car itself can be isolated for the first time, and its spectrum unambiguously analyzed. The X-ray emission of Eta Car in the 22-100 keV energy range is very hard (photon index around 1) and its luminosity is 7E33 erg/s. Conclusions : The observed emission is in agreement with the predictions of inverse Compton models, and corresponds to about 0.1% of the energy available in the wind collision. Eta Car is expected to be detected in the GeV energy range.

5 pages with 2 figures. Accepted as a Letter in Astronomy & Astrophysics

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• INTEGRAL/IBIS nine-year Galactic Hard X-Ray Survey
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• Eta Carinae's Thermal X-ray Tail Measured with XMM-Newton and NuSTAR
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• Suzaku Monitoring of Hard X-ray Emission from Eta Carinae over a Single Binary Orbital Cycle
• Five new INTEGRAL unidentified hard X-Ray sources uncovered by Chandra
• Colliding-wind binary systems: Diffusive shock acceleration and non-thermal emission
• Particle acceleration in the expanding blast wave of Eta Carina's Great Eruption of 1843
• 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
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• NuSTAR Observations of Magnetar 1E 1048.1-5937
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• Search for non-thermal X-ray emission in the colliding wind binary Cyg OB2 #8A
• Constraints on the non-thermal emission from Eta Carinae's blast wave of 1843
• $\eta$ Carinae: particle acceleration and multi-messenger aspects