Hot white dwarfs and pre-white dwarfs discovered with SALT

TL;DR

This paper reports the discovery and analysis of eight extremely hot white dwarf and pre-white dwarf stars, including the hottest known examples, providing insights into stellar evolution and pulsation stability.

Contribution

It presents the identification and detailed characterization of eight new very hot white and pre-white dwarf stars, expanding knowledge of their properties and evolutionary states.

Findings

Discovered eight new stars with temperatures over 100,000 K.

Identified the hottest GW Vir and DO white dwarf stars.

Included the first central star of a newly-discovered planetary nebula.

Abstract

The Southern African Large Telescope (SALT) survey of helium-rich hot subdwarfs aims to explore evolutionary pathways amongst groups of highly-evolved stars. The selection criteria mean that several hot white dwarfs and related objects have also been included. This paper reports the discovery and analysis of eight new very hot white dwarf and pre-white dwarf stars with effective temperatures exceeding 100,000 K. They include two PG1159 stars, one DO white dwarf, three O(He) and two O(H) stars. One of the O(H) stars is the central star of a newly-discovered planetary nebula, the other is the hottest `naked' O(H) star. Both of the PG1159 stars are GW Vir variables, one being the hottest GW Vir star measured and a crucial test for pulsation stability models. The DO white dwarf is also the hottest in its class.