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Hydrogen delivery onto white dwarfs from remnant exo-Oort cloud comets
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Veras, Dimitri, Shannon, Andrew and Gänsicke, B. T. (Boris T.) (2014) Hydrogen delivery onto white dwarfs from remnant exo-Oort cloud comets. Monthly Notices of the Royal Astronomical Society, Volume 445 (Number 4). pp. 4175-4185. doi:10.1093/mnras/stu2026 ISSN 0035-8711.
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Official URL: http://dx.doi.org/10.1093/mnras/stu2026
Abstract
The origin of trace hydrogen in white dwarfs (WDs) with He-dominated atmospheres is a long-standing problem, one that cannot satisfactorily be explained by the historically-favoured hypothesis of accretion from the interstellar medium. Here we explore the possibility that the gradual accretion of exo-Oort cloud comets, which are a rich source of H, contributes to the apparent increase of trace H with WD cooling age. We determine how often remnant exo-Oort clouds, freshly excited from post-main-sequence stellar mass loss, dynamically inject comets inside the WD's Roche radius. We improve upon previous studies by considering a representative range of single WD masses (0.52-1.00 Solar masses) and incorporating different cloud architectures, giant branch stellar mass loss, stellar flybys, Galactic tides and a realistic escape ellipsoid in self-consistent numerical simulations that integrate beyond 8 Gyr ages of WD cooling. We find that about 10^{-5} of the material in an exo-Oort cloud is typically amassed onto the WD, and that the H deposits accumulate even as the cloud dissipates. This accumulation may account for the relatively large amount of trace H, 10^{22}-10^{25} g, that is determined frequently among WDs with cooling ages >= 1 Gyr. Our results also reaffirm the notion that exo-Oort cloud comets are not the primary agents of the metal budgets observed in polluted WD atmospheres.
| Item Type: | Journal Article | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||
| Journal or Publication Title: | Monthly Notices of the Royal Astronomical Society | ||||||||
| Publisher: | Oxford University Press | ||||||||
| ISSN: | 0035-8711 | ||||||||
| Official Date: | 2014 | ||||||||
| Dates: |
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| Volume: | Volume 445 | ||||||||
| Number: | Number 4 | ||||||||
| Page Range: | pp. 4175-4185 | ||||||||
| DOI: | 10.1093/mnras/stu2026 | ||||||||
| Status: | Peer Reviewed | ||||||||
| Publication Status: | Published | ||||||||
| Access rights to Published version: | Restricted or Subscription Access |
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