No Neon, but Jets in the Remarkable Recurrent Nova M31N 2008-12a? - Hubble Space Telescope Spectroscopy of the 2015 Eruption

TL;DR

This study uses Hubble and Keck spectroscopy to analyze the 2015 eruption of the recurrent nova M31N 2008-12a, revealing high-velocity ejecta without neon signatures, and providing insights into its composition and eruption characteristics.

Contribution

First ultraviolet spectroscopic analysis of M31N 2008-12a's eruption, constraining reddening and ejecta properties, and examining white dwarf composition clues.

Findings

Detected highly ionized, high-velocity ejecta early after eruption

No evidence of neon in the spectra, questioning white dwarf composition

Constrained reddening to E(B-V) = 0.10 +/- 0.03

Abstract

The 2008 discovery of an eruption of M31N 2008-12a began a journey on which the true nature of this remarkable recurrent nova continues to be revealed. M31N 2008-12a contains a white dwarf close to the Chandrasekhar limit, accreting at a high rate from its companion, and undergoes thermonuclear eruptions which are observed yearly and may even be twice as frequent. In this paper, we report on Hubble Space Telescope Space Telescope Imaging Spectrograph ultraviolet spectroscopy taken within days of the predicted 2015 eruption, coupled with Keck spectroscopy of the 2013 eruption. Together, this spectroscopy permits the reddening to be constrained to E(B-V) = 0.10 +/- 0.03. The UV spectroscopy reveals evidence for highly ionized, structured, and high velocity ejecta at early times. No evidence for neon is seen in these spectra however, but it may be that little insight can be gained regarding the composition of the white dwarf (CO vs ONe).