Gamma-Ray Emission Concurrent with the Nova in the Symbiotic Binary V407 Cygni

TL;DR

This paper reports the first detection of gamma-ray emission from a nova in a symbiotic binary, suggesting particle acceleration in the nova shell interacting with the dense stellar environment.

Contribution

It presents the discovery of gamma-ray emission from V407 Cygni and proposes a model involving particle acceleration from nova shell interactions with the red giant's dense medium.

Findings

Detection of variable gamma-ray emission from V407 Cygni

Evidence supporting particle acceleration in nova shocks

Potential contribution of inverse Compton scattering

Abstract

Novae are thermonuclear explosions on a white dwarf surface fueled by mass accreted from a companion star. Current physical models posit that shocked expanding gas from the nova shell can produce X-ray emission but emission at higher energies has not been widely expected. Here, we report the Fermi Large Area Telescope detection of variable gamma-ray (0.1-10 GeV) emission from the recently-detected optical nova of the symbiotic star V407 Cygni. We propose that the material of the nova shell interacts with the dense ambient medium of the red giant primary, and that particles can be accelerated effectively to produce pi0 decay gamma-rays from proton-proton interactions. Emission involving inverse Compton scattering of the red giant radiation is also considered and is not ruled out.