White dwarfs as probes of extrasolar planet compositions and fundamental astrophysics

TL;DR

This paper discusses how the Habitable World Observatory can use white dwarf spectroscopy to study exoplanet compositions and test fundamental physics, leveraging high-resolution ultraviolet observations.

Contribution

It proposes specific science cases for HWO, including measuring heavy elements in white dwarfs and testing variations in fundamental constants.

Findings

HWO can measure heavy elements like S, C, O, Fe, Si in white dwarfs.

It can constrain water content and core composition of exoplanets.

Potential to detect variations in the fine structure constant.

Abstract

White dwarfs represent the most common end stage of stellar evolution and are important for a range of astrophysical questions. The high-resolution ultraviolet spectroscopic capability of the Habitable World Observatory (HWO) offers a unique capability to characterize white dwarfs. In this documents, we focus on two specific science cases for HWO -- white dwarfs as probes of extrasolar planet compositions, and fundamental astrophysics. HWO will have the sensitivity to measure a suite of heavy elements, such as S, C, O, Fe, and Si, in a large sample of polluted white dwarfs to constrain the water content and the light elements in the cores of extrasolar planets. HWO can also be used to search for any small variation on the fine structure constant in the presence of strong gravity. Both science cases require a minimum resolving power of 60,000, and a ultraviolet coverage down to at least 900 Angstrom.