Magnesium abundances in cool metal-polluted white dwarfs

Blouin, Simon

doi:10.1093/mnras/staa1689

Title: Magnesium abundances in cool metal-polluted white dwarfs

Journal Article · Sat Jun 13 00:00:00 EDT 2020 · Monthly Notices of the Royal Astronomical Society

DOI:https://doi.org/10.1093/mnras/staa1689· OSTI ID:1635139

^[1]

Los Alamos National Laboratory, PO Box 1663, Mail Stop P365, Los Alamos, NM 87545, USA

ABSTRACT The accretion of rocky material is responsible for the presence of heavy elements in the atmospheres of a large fraction of white dwarf stars. Those objects represent a unique opportunity to infer the bulk composition of exoplanetesimals. This chemical characterization requires the use of detailed atmosphere models to determine the elemental abundances at the photospheres of white dwarfs. In this work, we use a state-of-the-art model atmosphere code to reanalyse the first large survey of metal-polluted white dwarfs for which abundances are found for multiple elements. We show that the improved constitutive physics of our models lead to systematically higher Mg abundances than previous analyses. We find an average $$\log \, {\rm Mg/Ca}$$ number abundance ratio of 1.5. This value is significantly above the reference abundance for chondrites, which is expected as current diffusion models predict that for the cool helium-atmosphere white dwarfs of our sample, Mg should remain in the atmosphere longer than Ca. This helps resolve a recently identified Mg depletion problem, where the planetesimals accreted by white dwarfs were reported to be Mg-deficient compared to the expected composition of their planetary systems.

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Research Organization:: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

Sponsoring Organization:: USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE Office of Science (SC)

Grant/Contract Number:: 20190624PRD2; 89233218CNA000001

OSTI ID:: 1635139

Alternate ID(s):: OSTI ID: 1739995

Report Number(s):: LA-UR-20-23364

Journal Information:: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Vol. 496 Journal Issue: 2; ISSN 0035-8711

Publisher:: Royal Astronomical SocietyCopyright Statement

Country of Publication:: United Kingdom

Language:: English

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