Multi-wavelength observations of multiple eruptions of the recurrent nova M31N 2008-12a

TL;DR

This study presents multi-wavelength observations of recurrent nova M31N 2008-12a from 2017 to 2022, revealing decreasing accretion rates, jet-like features, and evidence supporting its potential as a Type Ia supernova progenitor.

Contribution

It provides detailed observational analysis and spectral modeling of multiple eruptions, highlighting accretion dynamics, ejecta properties, and the nova's significance in supernova progenitor scenarios.

Findings

Steady decrease in accretion rate over years.

Detection of a 'cusp' feature possibly linked to jets.

Mass ejection during eruptions estimated at 10^{-7} to 10^{-8} solar masses.

Abstract

We report the optical, UV, and soft X-ray observations of the $2017-2022$ eruptions of the recurrent nova M31N 2008-12a. We infer a steady decrease in the accretion rate over the years based on the inter-eruption recurrence period. We find a ``cusp'' feature in the $r'$ and $i'$ band light curves close to the peak, which could be associated to jets. Spectral modelling indicates a mass ejection of 10$^{-7}$ to 10$^{-8}$ M$_{\odot}$ during each eruption, and an enhanced Helium abundance of He/He$_{\odot}$ $\approx$ 3. The super-soft source (SSS) phase shows significant variability, which is anti-correlated to the UV emission, indicating a common origin. The variability could be due to the reformation of the accretion disk. A comparison of the accretion rate with different models on the $\rm M_{WD}$$-\dot{M}$ plane yields the mass of a CO WD, powering the ``H-shell flashes'' every $\sim$ 1 year to be $>1.36$ M$_{\odot}$ and growing with time, making M31N 2008-12a a strong candidate for the single degenerate scenario of Type Ia supernovae progenitor.