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Spectral analysis of ultra-cool white dwarfs polluted by planetary debris
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Elms, Abbigail K., Tremblay, Pier-Emmanuel, Gaensicke, B. T., Koester, Detlev., Hollands, Mark A., Gentile Fusillo, Nicola Pietro, Cunningham, T. J. and Apps, Kevin (2022) Spectral analysis of ultra-cool white dwarfs polluted by planetary debris. Monthly Notices of the Royal Astronomical Society, 517 (3). pp. 4557-4574. doi:10.1093/mnras/stac2908 ISSN 1365-2966.
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WRAP-spectral-analysis-ultra-cool-white-dwarfs-polluted-planetary-debris-2022.pdf - Accepted Version - Requires a PDF viewer. Download (2784Kb) | Preview |
Official URL: https://doi.org/10.1093/mnras/stac2908
Abstract
We identify two ultra-cool (${T_\mathrm{eff}}\lt 4000$ K) metal-polluted (DZ) white dwarfs WD J2147−4035 and WD J1922+0233 as the coolest and second coolest DZ stars known to date with ${T_\mathrm{eff}}\approx 3050$ K and ${T_\mathrm{eff}}\approx 3340$ K, respectively. Strong atmospheric collision-induced absorption (CIA) causes the suppression of red optical and infrared flux in WD J1922+0233, resulting in an unusually blue colour given its low temperature. WD J2147−4035 has moderate infrared CIA yet has the reddest optical colours known for a DZ white dwarf. Microphysics improvements to the non-ideal effects and CIA opacities in our model atmosphere code yields reasonable solutions to observations of these ultra-cool stars. WD J2147−4035 has a cooling age of over 10 Gyr which is the largest known for a DZ white dwarf, whereas WD J1922+0233 is slightly younger with a cooling age of 9 Gyr. Galactic kinematics calculations from precise Gaia EDR3 astrometry reveal these ultra-cool DZ stars as likely members of the Galactic disc thus they could be pivotal objects in future studies constraining an upper age limit for the disc of the Milky Way. We present intermediate-resolution spectroscopy for both objects, which provides the first spectroscopic observations of WD J2147−4035. Detections of sodium and potassium are made in both white dwarfs, in addition to calcium in WD J1922+0233 and lithium in WD J2147−4035. We identify the magnetic nature of WD J2147−4035 from Zeeman splitting in the lithium line and also make a tentative detection of carbon, so we classify this star as DZQH. WD J1922+0233 likely accreted planetary crust debris, while the debris composition that polluted WD J2147−4035 remains unconstrained.
| Item Type: | Journal Article | |||||||||||||||
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| Subjects: | Q Science > QB Astronomy | |||||||||||||||
| Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | |||||||||||||||
| SWORD Depositor: | Library Publications Router | |||||||||||||||
| Library of Congress Subject Headings (LCSH): | White dwarf stars , Space debris, Interstellar matter, Space environment, Space pollution | |||||||||||||||
| Journal or Publication Title: | Monthly Notices of the Royal Astronomical Society | |||||||||||||||
| Publisher: | Oxford University Press (OUP) | |||||||||||||||
| ISSN: | 1365-2966 | |||||||||||||||
| Official Date: | December 2022 | |||||||||||||||
| Dates: |
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| Volume: | 517 | |||||||||||||||
| Number: | 3 | |||||||||||||||
| Page Range: | pp. 4557-4574 | |||||||||||||||
| DOI: | 10.1093/mnras/stac2908 | |||||||||||||||
| Status: | Peer Reviewed | |||||||||||||||
| Publication Status: | Published | |||||||||||||||
| Reuse Statement (publisher, data, author rights): | This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record Abbigail K Elms, Pier-Emmanuel Tremblay, Boris T Gänsicke, Detlev Koester, Mark A Hollands, Nicola Pietro Gentile Fusillo, Tim Cunningham, Kevin Apps, Spectral analysis of ultra-cool white dwarfs polluted by planetary debris, Monthly Notices of the Royal Astronomical Society, Volume 517, Issue 3, December 2022, Pages 4557–4574, is available online at: https://doi.org/10.1093/mnras/stac2908 | |||||||||||||||
| Access rights to Published version: | Open Access (Creative Commons) | |||||||||||||||
| Date of first compliant deposit: | 15 December 2022 | |||||||||||||||
| Date of first compliant Open Access: | 15 December 2022 | |||||||||||||||
| RIOXX Funder/Project Grant: |
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