Discovery and Detailed Study of the M31 Classical Nova AT 2023tkw: Evidence for Internal Shocks

TL;DR

This paper analyzes a slow classical nova in M31, revealing evidence for internal shocks that cause multiple peaks in its light curve and spectral deviations, advancing understanding of nova eruption mechanisms.

Contribution

It provides the first detailed observational evidence linking internal shocks to multiple peaks in a slow nova's light curve and models the binary system components.

Findings

Multiple peaks caused by internal shocks within the nova.

Spectral deviations indicating shock-induced heating.

Estimated ejecta mass of approximately 10^{-4} solar masses.

Abstract

We present a detailed analysis of an extragalactic slow classical nova in M31 exhibiting multiple peaks in its light curve. Spectroscopic and photometric observations were used to investigate the underlying physical processes. Shock-induced heating events resulting in the expansion and contraction of the photosphere are likely responsible for the observed multiple peaks. Deviation of the observed spectrum at the peak from the models also suggests the presence of shocks. The successive peaks occurring at increasing intervals could be due to the series of internal shocks generated near or within the photosphere. Spectral modeling suggests a low-mass white dwarf accreting slowly from a companion star. The ejecta mass, estimated from spectral analysis, is $\sim 10^{-4}\mathrm{M_{\odot}}$, which is typical for a slow nova. We estimate the binary, by comparing the archival HST data and eruption properties with stellar and novae models, to comprise a 0.65 $\mathrm{M_{\odot}}$ primary white dwarf and a K III cool evolved secondary star.