Revealing the True Nature of Hen 2-428

Nicole Reindl,Martin Barstow,Sarah Casewell,Stephan Geier,Nicolle Finch,Veronika Schaffenroth,Stefan Taubenberger,Marcelo Miller Bertolami

doi:10.3390/galaxies6030088

Nicole Reindl, Martin Barstow + Show 6 more

Open Access

https://doi.org/10.3390/galaxies6030088

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Abstract

The nucleus of Hen 2-428 is a short orbital period (4.2 h) spectroscopic binary, whose status as potential supernovae type Ia progenitor has raised some controversy in the literature. We present preliminary results of a thorough analysis of this interesting system, which combines quantitative non-local thermodynamic (non-LTE) equilibrium spectral modelling, radial velocity analysis, multi-band light curve fitting, and state-of-the art stellar evolutionary calculations. Importantly, we find that the dynamical system mass that is derived by using all available He II lines does not exceed the Chandrasekhar mass limit. Furthermore, the individual masses of the two central stars are too small to lead to an SN Ia in case of a dynamical explosion during the merger process.

Highlights

The detection and study of progenitor systems of type Ia supernovae (SN Ia) are crucial to understand the exact explosion mechanism of these important cosmic distance indicators
By fitting the radial velocities (RVs) and light curves, they concluded that the system consists of two pre-white dwarfs with equal masses of 0.88 M
Our effective temperatures are significantly larger than the ones reported by [5], who derived the stellar temperatures from light curve fitting

Summary

Introduction

The detection and study of progenitor systems of type Ia supernovae (SN Ia) are crucial to understand the exact explosion mechanism of these important cosmic distance indicators. Santander-Garcia et al [5] have claimed to have discovered the first definite double-degenerate, super-Chandrasekhar system that will merge within a Hubble time, namely the central stars of the planetary nebula (CSPN) Hen 2-428. By fitting the radial velocities (RVs) and light curves, they concluded that the system consists of two pre-white dwarfs with equal masses of 0.88 M In this case, the system would merge within 700 million years making, Hen 2-428 one of the best SN Ia progenitor candidates known. We use an improved approach for the analysis of this unique object by combining quantitative non-LTE spectral modelling, RV analysis, multi-band light curve fitting, and state-of-the art stellar evolutionary calculations

Spectral Analysis

Light Curve Modelling

Dynamical Masses

Discussion

Conclusions