Constraints on the non-thermal emission from Eta Carinae's blast wave of 1843

TL;DR

This study investigates non-thermal emissions from Eta Carinae's 1843 blast wave, using archival X-ray data and modeling to constrain particle acceleration mechanisms and spectral properties.

Contribution

It provides new limits on non-thermal X-ray emission from Eta Carinae's blast wave and develops a model linking X-ray and gamma-ray observations to particle acceleration.

Findings

No shell-like structure detected in hard X-rays.

Constraints imply a very hard electron spectrum with Gamma < 1.8.

Abstract

Non-thermal hard X-ray and high-energy (HE; 1 MeV < E < 100 GeV) gamma-ray emission in the direction of Eta Carinae has been recently detected using the INTEGRAL, AGILE and Fermi satellites. This emission has been interpreted either in the framework of particle acceleration in the colliding wind region between the two massive stars or in the very fast moving blast wave which originates in the historical 1843 "Great Eruption". Archival Chandra data has been reanalysed to search for signatures of particle acceleration in Eta Carinae's blast wave. No shell-like structure could be detected in hard X-rays and a limit has been placed on the non-thermal X-ray emission from the shell. The time dependence of the target radiation field of the Homunculus is used to develop a single zone model for the blast wave. Attempting to reconcile the X-ray limit with the HE -ray emission using this model leads to a very hard electron injection spectrum dN/dE ~ E^-Gamma with Gamma < 1.8, harder than the canonical value expected from diffusive shock acceleration.