On the Evolution of the Late-time {\it Hubble Space Telescope} Imaging of the Outburst of the Recurrent Nova RS Ophiuchi (2006)

TL;DR

This paper models late-time Hubble Space Telescope images of RS Ophiuchi's 2006 outburst, analyzing nebular evolution and emission lines to understand the dynamics of the expanding nova remnant.

Contribution

It provides a detailed model of the nebular evolution and emission line origins in RS Ophiuchi's 2006 outburst, addressing previous uncertainties due to lack of simultaneous spectroscopy.

Findings

Outer material expands linearly with time

Inner over-density may have decelerated or remained static

Forbidden lines are absent in the spectra

Abstract

We modelled the late-time {\it Hubble Space Telescope} imaging of RS Ophiuchi with models from Ribeiro et al. (2009), which at the time due to the unknown availability of simultaneous ground-based spectroscopy left some open questions as to the evolution of the expanding nebular from the early to the late time observations. Initial emission line identifications suggest that no forbidden lines are present in the spectra and that the emission lines arising in the region of the WFPC2 F502N images are due to N{\sc ii} and He{\sc i} + Fe{\sc ii}. The best model fit to the spectrum is one where the outer faster moving material expands linearly with time while the inner over-density material either suffered some deceleration or did not change in physical size. The origin of this inner over-density requires further exploration.