The discovery of a population of gamma-ray novae

TL;DR

This paper reports the discovery and analysis of gamma-ray emission from a population of novae, revealing that such high-energy emissions are more common than previously thought and are linked to shock interactions.

Contribution

It introduces the first systematic study of gamma-ray novae, expanding understanding of their emission mechanisms and prevalence in our galaxy.

Findings

Gamma-ray novae are more numerous than previously believed.

High-energy emission is associated with shock interactions in nova ejecta.

The properties of gamma-ray novae show both similarities and differences, informing emission models.

Abstract

Novae have long been expected to be sources of emission at several MeV from the decay of radioactive elements in the novae ejecta, however, they were not anticipated to be sources of continuum emission in the GeV energy domain. In March 2010 the Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope discovered for the first time >100 MeV gamma-ray emission from a nova within our galaxy, V407 Cyg. The high-energy spectrum and light curve was explained as a consequence of shock acceleration in the nova shell as it interacts with the local ambient medium. While this was an exciting and important discovery it was suspected that the necessary conditions for high-energy emission from novae would be rare. In June 2012 the LAT detected two new transient sources that have been associated with classical novae observed in the optical, Nova Sco 2012 and Nova Mon 2012. We report on the observational properties of the population of gamma-ray novae, their similarities and differences and the emission processes that generate the high energy radiation in these systems.