The planetary nebula Abell 48 and its [WN4] central star

TL;DR

This study reclassifies the central star of planetary nebula Abell 48 as a hydrogen-deficient [WN4] star, clarifying its nature and evolutionary status through multi-wavelength observations and nebular analysis.

Contribution

It provides the first detailed classification of Abell 48's central star as a [WN4] type and clarifies its nebular properties, distinguishing it from massive star ejecta.

Findings

The nebula is typical of planetary nebulae, not massive star ejecta.

The ionized mass at 2 kpc is consistent with a moderate evolved planetary nebula.

The central star's luminosity is about 5000 L_sun, typical for PN central stars.

Abstract

We have conducted a multi-wavelength study of the planetary nebula Abell 48 and give a revised classification of its nucleus as a hydrogen-deficient star of type [WN4]. The surrounding nebula has a morphology typical of PNe and importantly, is not enriched in nitrogen, and thus not the 'peeled atmosphere' of a massive star. Indeed, no WN4 star is known to be surrounded by such a compact nebula. The ionized mass of the nebula is also a powerful discriminant between the low-mass PN and high-mass WR ejecta interpretations. The ionized mass would be impossibly high if a distance corresponding to a Pop I star was adopted, but at a distance of 2 kpc, the mass is quite typical of moderately evolved PNe. At this distance, the ionizing star then has a luminosity of ~5000 Lsolar, again rather typical for a PN central star. We give a brief discussion of the implications of this discovery for the late-stage evolution of intermediate-mass stars.