Compositions of Planetary Debris around Dusty White Dwarfs

TL;DR

This study analyzes the chemical compositions of planetary debris accreted onto white dwarfs, revealing diverse elemental ratios and evidence of evaporation processes, which enhances understanding of exoplanetary material compositions.

Contribution

It provides spectroscopic analysis of 19 white dwarfs with planetary debris, revealing diverse compositions and evidence of evaporation sequences, expanding knowledge of exoplanetary material.

Findings

Resemblance to bulk Earth composition

Detection of Fe-rich and O-rich debris

Elemental ratio variations follow evaporation sequence

Abstract

The photospheres of some white dwarfs are "polluted" by accretion of material from their surrounding planetary debris. White dwarfs with dust disks are often heavily polluted and high-resolution spectroscopic observations of these systems can be used to infer the chemical compositions of extrasolar planetary material. Here, we report spectroscopic observation and analysis of 19 white dwarfs with dust disks or candidate disks. The overall abundance pattern very much resembles that of bulk Earth and we are starting to build a large enough sample to probe a wide range of planetary compositions. We found evidence for accretion of Fe-rich material onto two white dwarfs as well as O-rich but H-poor planetary debris onto one white dwarf. In addition, there is a spread in Mg/Ca and Si/Ca ratios and it cannot be explained by differential settling or igneous differentiation. The ratios appear to follow an evaporation sequence. In this scenario, we can constrain the mass and number of evaporating bodies surrounding polluted white dwarfs.