Does a Differentiated, Carbonate-Rich, Rocky Object Pollute the White Dwarf SDSSJ104341.53+085558.2?

TL;DR

This study analyzes the composition of a polluted white dwarf star, revealing that it accretes material similar to Earth's outer layers, with evidence suggesting the presence of carbonate minerals in the parent body.

Contribution

It provides detailed elemental analysis of SDSSJ1043+0855, indicating accretion of differentiated, carbonate-rich rocky material, and demonstrates how polluted white dwarfs can reveal exoplanetary interior structures.

Findings

The parent body is rocky and iron-poor, similar to the Moon or Earth's outer layers.

Evidence of carbonate minerals up to 9% calcium carbonate by mass.

Polluted white dwarfs can be used to study the structure of exoplanetary bodies.

Abstract

We present spectroscopic observations of the dust- and gas-enshrouded, polluted, single white dwarf star SDSSJ104341.53+085558.2 (hereafter SDSSJ1043+0855). Hubble Space Telescope Cosmic Origins Spectrograph far-ultraviolet spectra combined with deep Keck HIRES optical spectroscopy reveal the elements C, O, Mg, Al, Si, P, S, Ca, Fe, and Ni and enable useful limits for Sc, Ti, V, Cr, and Mn in the photosphere of SDSSJ1043+0855. From this suite of elements we determine that the parent body being accreted by SDSSJ1043+0855 is similar to the silicate Moon or the outer layers of Earth in that it is rocky and iron-poor. Combining this with comparison to other heavily polluted white dwarf stars, we are able to identify the material being accreted by SDSSJ1043+0855 as likely to have come from the outermost layers of a differentiated object. Furthermore, we present evidence that some polluted white dwarfs (including SDSSJ1043+0855) allow us to examine the structure of differentiated extrasolar rocky bodies. Enhanced levels of carbon in the body polluting SDSSJ1043+0855 relative to the Earth-Moon system can be explained with a model where a significant amount of the accreted rocky minerals took the form of carbonates; specifically, through this model the accreted material could be up to 9% calcium-carbonate by mass.