Probing cosmic ray escape from η Carinae

Abstract

The binary stellar system η Carinae is one of very few established astrophysical hadron accelerators. It seems likely that at least some fraction of the particles accelerated by η Carinae escape from the system. Copious target material for hadronic interactions and associated γ-ray emission exist on a wide range of spatial scales outside the binary system. This material creates a unique opportunity to trace the propagation of particles into the interstellar medium. In this work, we analyse γ-ray data from Fermi-LAT of η Carinae and surrounding molecular clouds and investigate the many different scales on which escaping particles may interact and produce γ-rays. We find that interactions of escaping cosmic rays from η Carinae in the wind region and the Homunculus Nebula could produce a significant contribution to the γ-ray emission associated with the system. Furthermore, we detect excess emission from the surrounding molecular clouds. The derived radial cosmic-ray excess profile is consistent with a steady injection of cosmic rays by a central source. However, this would require a higher flux of escaping cosmic rays from η Carinae than provided by our model. Therefore, it is likely that additional cosmic ray sources contribute to the hadronic γ-ray emission from the clouds.