Wilson, D. J., Gansicke, B. T., Koester, D. et al. (4 more authors) (2015) The composition of a disrupted extrasolar planetesimal at SDSS J0845+2257 (Ton 345). Monthly Notices of the Royal Astronomical Society, 451 (3). pp. 3237-3248. ISSN 0035-8711
Abstract
We present a detailed study of the metal-polluted DB white dwarf SDSS J0845+2257 (Ton 345). Using high-resolution Hubble Space Telescope/Cosmic Origins Spectrograph and Very Large Telescope spectroscopy, we have detected hydrogen and 11 metals in the atmosphere of the white dwarf. The origin of these metals is almost certainly the circumstellar disc of dusty and gaseous debris from a tidally disrupted planetesimal, accreting at a rate of 1.6 × 1010 g s−1. Studying the chemical abundances of the accreted material demonstrates that the planetesimal had a composition similar to the Earth, dominated by rocky silicates and metallic iron, with a low water content. The mass of metals within the convection zone of the white dwarf corresponds to an asteroid of at least ∼130–170 km in diameter, although the presence of ongoing accretion from the debris disc implies that the planetesimal was probably larger than this. While a previous abundance study of the accreted material has shown an anomalously high mass fraction of carbon (15 per cent) compared to the bulk Earth, our independent analysis results in a carbon abundance of just 2.5 per cent. Enhanced abundances of core material (Fe, Ni) suggest that the accreted object may have lost a portion of its mantle, possibly due to stellar wind stripping in the asymptotic giant branch. Time series spectroscopy reveals variable emission from the orbiting gaseous disc, demonstrating that the evolved planetary system at SDSS J0845+2257 is dynamically active.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Reproduced in accordance with the publisher's self-archiving policy. |
Keywords: | planets and satellites: composition; stars: individual: SDSS J0845+2257; planetary systems; white dwarfs |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > Department of Physics and Astronomy (Sheffield) |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 28 Nov 2016 15:07 |
Last Modified: | 28 Nov 2016 15:07 |
Published Version: | http://dx.doi.org/10.1093/mnras/stv1201 |
Status: | Published |
Publisher: | Oxford University Press (OUP): Policy P - Oxford Open Option A |
Refereed: | Yes |
Identification Number: | 10.1093/mnras/stv1201 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:108482 |