Multi-Epoch Radio Imaging of gamma-ray Nova V959 Mon

TL;DR

This paper presents multi-epoch high-resolution radio imaging of gamma-ray nova V959 Mon, revealing morphological evolution of the ejecta from east-west to north-south, enhancing understanding of nova ejecta behavior.

Contribution

It provides the first detailed high-resolution radio images over multiple epochs showing morphological changes in nova ejecta.

Findings

Ejecta initially elongated east-west

Ejecta later elongated north-south

Morphological evolution observed over time

Abstract

V959 Mon (Nova Mon 2012) was first detected by the Fermi Large Area Telescope in June 2012, as a transient gamma-ray source. Subsequent optical observations showed that this gamma-ray emission was due to a classical nova explosion. Multi-frequency observations of V959 Mon with the VLA between June and September 2012 revealed dramatic brightening, and a spectrum that steepened with increasing frequency. High resolution radio images of V959 Mon using e-MERLIN are presented here, at six epochs between September 2012 and February 2014 which show morphological evolution of the source. While early e-MERLIN observations of V959 Mon show an east-west elonga- tion in the ejecta morphology, subsequent observations suggest that the ejecta become elongated in the north-south direction. Our high-resolution observations of this sur- prising evolution in the structure of V959 Mon can assist us in further understanding the behaviour and morphology of nova ejecta.