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    Extreme abundance ratios in the polluted atmosphere of the cool white dwarf NLTT 19868

    271965.pdf (356.5Kb)
    Access Status
    Open access
    Authors
    Kawka, Adela
    Vennes, S.
    Date
    2016
    Type
    Journal Article
    
    Metadata
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    Citation
    Kawka, A. and Vennes, S. 2016. Extreme abundance ratios in the polluted atmosphere of the cool white dwarf NLTT 19868. Monthly Notices of the Royal Astronomical Society. 458 (1): pp. 325-331.
    Source Title
    Monthly Notices of the Royal Astronomical Society
    DOI
    10.1093/mnras/stw383
    ISSN
    0035-8711
    School
    Curtin Institute of Radio Astronomy (Physics)
    Remarks

    This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

    URI
    http://hdl.handle.net/20.500.11937/71932
    Collection
    • Curtin Research Publications
    Abstract

    We present an analysis of intermediate-dispersion spectra and photometric data of the newly identified cool, polluted white dwarf NLTT 19868. The spectra obtained with X-shooter on the Very Large Telescope-Melipal show strong lines of calcium, and several lines of magnesium, aluminium and iron. We use these spectra and the optical-to-near-infrared spectral energy distribution to constrain the atmospheric parameters of NLTT 19868. Our analysis shows that NLTT 19868 is iron poor with respect to aluminium and calcium. A comparison with other cool, polluted white dwarfs shows that the Fe to Ca abundance ratio (Fe/Ca) varies by up to approximately two orders of magnitudes over a narrow temperature range with NLTT 19868 at one extremum in the Fe/Ca ratio and, in contrast, NLTT 888 at the other extremum. The sample shows evidence of extreme diversity in the composition of the accreted material: in the case of NLTT 888, the inferred composition of the accreted matter is akin to iron-rich planetary core composition, while in the case of NLTT 19868 it is close to mantle composition depleted by subsequent chemical separation at the bottom of the convection zone.

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