A lepto-hadronic model of gamma rays from the Eta Carinae and prospects for neutrino telescopes

Abstract

The stellar binary $\eta$ Carinae has been observed during its full orbital period in gamma rays by the Fermi-Large Area Telescope (LAT). The shock-accelerated electrons in the colliding winds of the two stars radiate synchrotron photons in the magnetic field of the shocked region and inverse Compton photons, where the target photons are from the thermal emissions by the more massive and luminous of the two stars. The inverse Compton emission dominates the gamma-ray flux data from the $\eta$ Carinae, however the spectral energy distribution shows signature of a hadronic component in the $\sim 10$-300 GeV range during the periastron passage. Current and future air Cherenkov telescopes will be able to constrain this component at TeV energies. Acceleration of cosmic-ray protons to $\gg 1$ TeV energies in the colliding winds, required to explain the hadronic emission component through photopion interactions, can lead to detectable signal of $\gtrsim 10$ TeV neutrino events in large kilometer scale neutrino telescopes.

Comments: 8 pages and 5 figures. Added gamma-gamma pair production calculation and expanded discussion. Main results unchanged. Accepted in Phys. Rev. D