The Origins of Lithium Enhancement in Polluted White Dwarfs
The bulk abundances of exoplanetesimals can be measured when they are accreted by white dwarfs. Recently, lithium from the accretion of exoplanetesimals was detected in relatively high levels in multiple white dwarfs. There are presently three proposed hypotheses to explain the detection of excess l...
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ad9a6d |
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| author | Benjamin C. Kaiser J. Christopher Clemens Simon Blouin Erik Dennihy Patrick Dufour Ryan J. Hegedus Joshua S. Reding |
| author_facet | Benjamin C. Kaiser J. Christopher Clemens Simon Blouin Erik Dennihy Patrick Dufour Ryan J. Hegedus Joshua S. Reding |
| author_sort | Benjamin C. Kaiser |
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| description | The bulk abundances of exoplanetesimals can be measured when they are accreted by white dwarfs. Recently, lithium from the accretion of exoplanetesimals was detected in relatively high levels in multiple white dwarfs. There are presently three proposed hypotheses to explain the detection of excess lithium in white dwarf photospheres: Big Bang and Galactic nucleosynthesis, continental crust, and an exomoon formed from spalled ring material. We present new observations of three previously known lithium-polluted white dwarfs (WD J1824+1213, WD J2317+1830, and LHS 2534), and one with metal pollution without lithium (SDSS J1636+1619). We also present atmospheric model fits to these white dwarfs. We then evaluate the abundances of these white dwarfs and two additional lithium-polluted white dwarfs that were previously fit using the same atmospheric models (WD J1644-0449 and SDSS J1330+6435) in the context of the three extant hypotheses for explaining lithium excesses in polluted white dwarfs. We find Big Bang and Galactic nucleosynthesis to be the most plausible explanation of the abundances in WD J1644-0449, WD J1824+1213, and WD J2317+1830. SDSS J1330+6435 will require stricter abundances to determine its planetesimal’s origins, and LHS 2534, as presently modeled, defies all three hypotheses. We find the accretion of an exomoon formed from spalled ring material to be highly unlikely to be the explanation of the lithium excess in any of these cases. |
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| language | English |
| publishDate | 2025-01-01 |
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| spelling | doaj-art-2a107778d9644edf99a919ab261f0cf22025-08-20T01:54:04ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01979211110.3847/1538-4357/ad9a6dThe Origins of Lithium Enhancement in Polluted White DwarfsBenjamin C. Kaiser0https://orcid.org/0000-0003-1970-4684J. Christopher Clemens1Simon Blouin2https://orcid.org/0000-0002-9632-1436Erik Dennihy3https://orcid.org/0000-0003-2852-268XPatrick Dufour4https://orcid.org/0000-0003-4609-4500Ryan J. Hegedus5https://orcid.org/0000-0003-4145-3770Joshua S. Reding6https://orcid.org/0000-0003-1862-2951Department of Physics and Astronomy, University of North Carolina , 120 E. Cameron Avenue, Chapel Hill, NC 27599, USA ; ben.kaiser@unc.eduDepartment of Physics and Astronomy, University of North Carolina , 120 E. Cameron Avenue, Chapel Hill, NC 27599, USA ; ben.kaiser@unc.eduDepartment of Physics and Astronomy, University of Victoria , Victoria BC V8W 2Y2, CanadaGemini Observatory/NSF’s NOIRLab , Casilla 603, La Serena, Chile; Rubin Observatory Project Office , 950 N. Cherry Avenue, Tucson, AZ 85719, USADépartement de Physique, Université de Montréal , Montréal, QC H3C 3J7, Canada; Institut de Recherche sur les Exoplanétes (iREx), Université de Montréal , Montréal, QC H3C 3J7, CanadaDepartment of Physics and Astronomy, University of North Carolina , 120 E. Cameron Avenue, Chapel Hill, NC 27599, USA ; ben.kaiser@unc.eduDepartment of Physics and Astronomy, University of North Carolina , 120 E. Cameron Avenue, Chapel Hill, NC 27599, USA ; ben.kaiser@unc.eduThe bulk abundances of exoplanetesimals can be measured when they are accreted by white dwarfs. Recently, lithium from the accretion of exoplanetesimals was detected in relatively high levels in multiple white dwarfs. There are presently three proposed hypotheses to explain the detection of excess lithium in white dwarf photospheres: Big Bang and Galactic nucleosynthesis, continental crust, and an exomoon formed from spalled ring material. We present new observations of three previously known lithium-polluted white dwarfs (WD J1824+1213, WD J2317+1830, and LHS 2534), and one with metal pollution without lithium (SDSS J1636+1619). We also present atmospheric model fits to these white dwarfs. We then evaluate the abundances of these white dwarfs and two additional lithium-polluted white dwarfs that were previously fit using the same atmospheric models (WD J1644-0449 and SDSS J1330+6435) in the context of the three extant hypotheses for explaining lithium excesses in polluted white dwarfs. We find Big Bang and Galactic nucleosynthesis to be the most plausible explanation of the abundances in WD J1644-0449, WD J1824+1213, and WD J2317+1830. SDSS J1330+6435 will require stricter abundances to determine its planetesimal’s origins, and LHS 2534, as presently modeled, defies all three hypotheses. We find the accretion of an exomoon formed from spalled ring material to be highly unlikely to be the explanation of the lithium excess in any of these cases.https://doi.org/10.3847/1538-4357/ad9a6dWhite dwarf starsDZ starsBig Bang nucleosynthesisExoplanetsNucleosynthesis |
| spellingShingle | Benjamin C. Kaiser J. Christopher Clemens Simon Blouin Erik Dennihy Patrick Dufour Ryan J. Hegedus Joshua S. Reding The Origins of Lithium Enhancement in Polluted White Dwarfs The Astrophysical Journal White dwarf stars DZ stars Big Bang nucleosynthesis Exoplanets Nucleosynthesis |
| title | The Origins of Lithium Enhancement in Polluted White Dwarfs |
| title_full | The Origins of Lithium Enhancement in Polluted White Dwarfs |
| title_fullStr | The Origins of Lithium Enhancement in Polluted White Dwarfs |
| title_full_unstemmed | The Origins of Lithium Enhancement in Polluted White Dwarfs |
| title_short | The Origins of Lithium Enhancement in Polluted White Dwarfs |
| title_sort | origins of lithium enhancement in polluted white dwarfs |
| topic | White dwarf stars DZ stars Big Bang nucleosynthesis Exoplanets Nucleosynthesis |
| url | https://doi.org/10.3847/1538-4357/ad9a6d |
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