Fermi Reveals New Light on Novae in Gamma rays

TL;DR

Fermi observations have confirmed novae as a source of high-energy gamma rays, revealing different emission mechanisms in classical and symbiotic novae, and providing new insights into their particle acceleration processes.

Contribution

This paper summarizes Fermi-LAT gamma-ray observations of novae and reports the first soft gamma-ray detection of a classical nova with implications for understanding emission mechanisms.

Findings

Novae are confirmed as high-energy gamma-ray sources.

Different gamma-ray production mechanisms are suggested for classical and symbiotic novae.

Detection of soft gamma-ray continuum in a classical nova provides new observational constraints.

Abstract

Novae are now firmly established as a high-energy (>100 MeV) gamma-ray source class by the Fermi Large Area Telescope (LAT). In symbiotic binary systems such as V407 Cyg 2010, there is a firm theoretical framework for the production of shock-accelerated particles in the nova ejecta from interactions with the dense wind of the red giant companion. Yet, the high-energy gamma-ray emission detected in classical novae involving less evolved stellar companions cannot be explained in the same way and could instead be produced in internal shocks in the ejecta. We summarize the Fermi-LAT gamma-ray observations of novae, highlighting the main properties that will guide further studies. Additionally, we report on the soft gamma-ray (~0.1 MeV) continuum detection of the oxygen-neon type classical nova V382 Vel 1999 with the OSSE detector aboard the Compton Gamma Ray Observatory in light of its Fermi-era analog, V959 Mon 2012.