[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"doc-detail-127148-en":3,"doc-seo-127148-105":30,"detail-sidebar-cat-0-en-105":91},{"code":4,"msg":5,"data":6},0,"success",{"doc_id":7,"user_id":8,"nickname":9,"user_avatar":10,"doc_module":4,"category_id":11,"category_name":12,"doc_title":13,"doc_description":14,"doc_content":15,"file_id":16,"file_url":17,"file_type":18,"file_size":19,"view_count":4,"is_deleted":4,"is_public":20,"is_downloadable":20,"audit_status":20,"page_count":21,"language":22,"language_code":23,"site_id":24,"html_lang":23,"table_of_contents":25,"faqs":26,"seo_title":27,"seo_description":14,"update_tm":28,"read_time":29},127148,3985741905716,"Rowan","https://ap-avatar.wpscdn.com/davatar_994ba38a5ba835b3df7d355c54d3ed8d",8,"Research & Report","Hunting for Polluted White Dwarfs and Other Treasures with Gaia XP Spectra and Unsupervised Machine Learning","White dwarfs polluted by exoplanetary material enable direct study of exoplanet interiors, but spectroscopic searches are constrained by brightness and the intrinsic faintness of large WD samples. This work targets a substantial increase in multi-metal WDs by analyzing 96,134 Gaia DR3 BP/RP (XP) spectra. An unsupervised UMAP-based 2D organization yields identifiable spectral regions, including a polluted group. The approach could raise the count of WDs with five or more metal species by about an order of magnitude, supporting studies of exoplanet diversity and geology.","arXiv :2405 . 17667v2 [ astro-ph . SR] 24 Jun 2024  \nDraft version June 26, 2024  \nTypeset using LATEX twocolumn style in AASTeX631  \nHunting for Polluted White Dwarfs and Other Treasures with Gaia XP Spectra and Unsupervised  \nMachine Learning  \nMalia L. Kao  ,1 Keith Hawkins  ,1 Laura K. Rogers  ,2 Amy Bonsor,2 Bart H. Dunlap  ,1 Jason L. Sanders  ,3 M. H. Montgomery  ,1 and D. E. Winget1  \n1 Department of Astronomy, University of Texas at Austin, 2515 Speedway, Austin, TX 78712, USA  \n2 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK  \n3 Department of Physics & Astronomy, University College London, Gower Street, London, WC1E 6BT, UK  \nABSTRACT  \nWhite dwarfs (WDs) polluted by exoplanetary material provide the unprecedented opportunity to directly observe the interiors of exoplanets. However, spectroscopic surveys are often limited by brightness constraints, and WDs tend to be very faint, making detections of large populations of polluted WDs difficult. In this paper, we aim to increase considerably the number of WDs with multiple metals in their atmospheres. Using 96,134 WDs with Gaia DR3 BP/RP (XP) spectra, we constructed a 2D map using an unsupervised machine learning technique called Uniform Manifold Approximation and Projection (UMAP) to organize the WDs into identifiable spectral regions. The polluted WDs are among the distinct spectral groups identified in our map. We have shown that this selection method could potentially increase the number of known WDs with 5 or more metal species in their atmospheres by an order of magnitude. Such systems are essential for characterizing exoplanet diversity and geology.  \nKeywords: White dwarf stars(1799)—DZ stars(1848)—Gaia(2360)  \n1. INTRODUCTION  \nThe death of a low-mass (≲ 8 M⊙ ) main-sequence star culminates in the ejection of its outer layers in a planetary nebula and the collapse of its core into a white dwarf (WD) . Typical mass WDs are extremely dense and have very high surface gravities (log g ∼ 8.0, central density ≈ 106 g/cm3 ), equivalent to about 100,000 times that of Earth. As such, WDs are chemically stratified, meaning lighter elements like H and He rise to the surface and heavier elements (e.g., C, O, Ca, Mg, Fe, etc.) sink to the core. The majority of WDs are expected to consist of carbon-oxygen cores and thin upper layers of He and H that make up only ∼ 1% of the total WD mass. Formost WD spectra, we expect the presence of H (DA) or He I (DB) absorption lines, or no spectral lines (DC) if the WD is cold enough to no longer excite atoms above their ground state (≲ 11,000 K for DBs and ≲ 5,000 K for DAs) . However, some WDs, especially cooler WDs, have been found with absorption features from heavier elements in their atmospheres. This has been interpreted as evidence for evolved planetary systems and surviving minor planets (Debes & Sigurdsson 2002; Jura 2003; Zuckerman et al. 2007; Koester et al. 2014) .  \nThe first WD observed with metal pollution in its atmosphere was discovered in 1917 (van Maanen 1917) . It was initially classified as an F-type star since its spectrum featured large amounts of Ca and Fe absorption. Six years later it was re-classified as a WD (Luyten 1923), a newly coined stellar type, but the astrophysical implications of this went unrealized until nearly a century later. Heavy metals on WD surfaces are expected to have short diffusion timescales, on the order of days to at most a few million years, relative to the WD cooling time. Therefore, the presence of heavy metal lines in WD spectra indicate that the metals cannot be primordial, but must be recently accreted from rocky material (Koester & Wilken 2006) . It was first conjectured that the metals were accreted from the interstellar medium (ISM) as older, and therefore cooler, WDs would have the chance to interact with dense ISM clouds frequently throughout their lifetimes, i.e., every 50 million years or so (Dupuis et al. 1993) . At the time, thi","cbCaifrG6O88uktC","https://ap.wps.com/l/cbCaifrG6O88uktC","pdf",2506533,1,16,"English","en",105,"# Abstract\n# Introduction","[{\"question\":\"Why are polluted white dwarfs important for exoplanet studies?\",\"answer\":\"Polluted white dwarfs contain exoplanetary material in their atmospheres, enabling direct observational access to processes tied to exoplanet interiors and composition.\"},{\"question\":\"What data and method are used to find polluted white dwarfs?\",\"answer\":\"The study uses 96,134 Gaia DR3 BP/RP (XP) spectra and applies an unsupervised machine learning technique, UMAP, to map spectra into identifiable regions.\"},{\"question\":\"How does the proposed selection method improve discovery rates?\",\"answer\":\"The polluted WDs appear as a distinct spectral group in the UMAP map, and the method could increase the number of known WDs with five or more metal species by roughly an order of magnitude.\"}]","Hunting for Polluted White Dwarfs and Other 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are polluted white dwarfs important for exoplanet studies?","Question",{"text":75,"@type":76},"Polluted white dwarfs contain exoplanetary material in their atmospheres, enabling direct observational access to processes tied to exoplanet interiors and composition.","Answer",{"name":78,"@type":73,"acceptedAnswer":79},"What data and method are used to find polluted white dwarfs?",{"text":80,"@type":76},"The study uses 96,134 Gaia DR3 BP/RP (XP) spectra and applies an unsupervised machine learning technique, UMAP, to map spectra into identifiable regions.",{"name":82,"@type":73,"acceptedAnswer":83},"How does the proposed selection method improve discovery rates?",{"text":84,"@type":76},"The polluted WDs appear as a distinct spectral group in the UMAP map, and the method could increase the number of known WDs with five or more metal species by roughly an order of 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