Is the central binary system of the planetary nebula Henize 2-428 a Type Ia supernova progenitor?

TL;DR

This paper critically examines the binary system at the center of planetary nebula Henize 2-428, challenging previous claims that it is a Type Ia supernova progenitor by proposing alternative interpretations of observational data.

Contribution

The study offers a revised analysis of the binary system, suggesting it is unlikely to be a double-degenerate system leading to a supernova, thus questioning prior assumptions.

Findings

The variability of the He II 5412A line is better explained by a broad absorption with a narrow emission line.

A binary system of a degenerate star and a low-mass main sequence star fits observations better.

The double-degenerate scenario for Henize 2-428 as a SN Ia progenitor is likely premature.

Abstract

We critically discuss the recent observations of the binary system at the center of the bipolar planetary nebula Henize 2-428. We find that the proposed explanation of two equal-mass degenerate objects with a total mass larger than the Chandrasekhar limiting mass that supposedly will merge in less than a Hubble time, possibly leading to a SN~Ia, is controversial. This hypothesis relies on the assumption that the variability of the He II 5412A spectral line is due to two absorption components. Instead, we propose that it can be accounted for by a broad absorption line from the central system on top of which there is a narrow emission line from the nebula. This prompted us to study if the binary system can be made of a degenerate star and a low-mass main sequence companion, or of two degenerate objects of smaller mass. We find that although both scenarios can account for the existence of two symmetric broad minima in the light curve, the second one agrees better with observations. We thus argue that the claim that Henize 2-428 provides observational evidence supporting the double-degenerate scenario for SN~Ia is premature.