Fermi Discovers a New Population of Gamma-ray Novae

TL;DR

Fermi LAT observations revealed novae as a new class of high-energy gamma-ray sources, providing insights into particle acceleration mechanisms and demonstrating gamma-ray detection independent of optical discovery.

Contribution

This paper reports the first detections of gamma-ray novae by Fermi LAT, establishing novae as a new gamma-ray source class and analyzing their high-energy emission mechanisms.

Findings

Novae are confirmed as gamma-ray sources by Fermi LAT.

Gamma-ray novae can be detected independently of optical observations.

Insights into particle acceleration in nova environments.

Abstract

Novae had not been widely considered as high-energy (>100 MeV) gamma-ray sources before the launch of the Fermi Large Area Telescope (LAT). In March 2010, the LAT made the first gamma-ray detection of a nova in the symbiotic binary V407 Cygni. The LAT observations uniquely probed the high-energy particle acceleration mechanism in the environs of the V407 Cyg binary system consisting of a white dwarf and its red giant companion. Subsequently in June 2012, two more novae were detected with the LAT, Nova Sco 2012 and Nova Mon 2012, thus heralding novae as a new gamma-ray source class. For Nova Mon 2012, the gamma-ray transient source was discovered first, followed by the optical confirmation of the nova, showcasing how novae can be found with the LAT independently from traditional optical searches. We discuss the LAT detected gamma-ray novae together with observational limits on other optical novae over the first four years of the Fermi mission and reconsider the possible high-energy gamma-ray production mechanisms in novae in light of the new detections.