Unusual Abundances from Planetary System Material Polluting the White Dwarf G238-44
| Autor: | Johnson, Ted M, Klein, Beth L., Koester, D., Melis, Carl, Zuckerman, B., Jura, M. |
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| Rok vydání: | 2022 |
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| Druh dokumentu: | Working Paper |
| DOI: | 10.3847/1538-4357/aca089 |
| Popis: | Ultraviolet and optical spectra of the hydrogen-dominated atmosphere white dwarf star G238-44 obtained with FUSE, Keck/HIRES, HST/COS, and HST/STIS reveal ten elements heavier than helium: C, N, O, Mg, Al, Si, P, S, Ca, and Fe. G238-44 is only the third white dwarf with nitrogen detected in its atmosphere from polluting planetary system material. Keck/HIRES data taken on eleven nights over 24 years show no evidence for variation in the equivalent width of measured absorption lines, suggesting stable and continuous accretion from a circumstellar reservoir. From measured abundances and limits on other elements we find an anomalous abundance pattern and evidence for the presence of metallic iron. If the pollution is from a single parent body, then it would have no known counterpart within the solar system. If we allow for two distinct parent bodies, then we can reproduce the observed abundances with a mix of iron-rich Mercury-like material and an analog of an icy Kuiper Belt object with a respective mass ratio of 1.7:1. Such compositionally disparate objects would provide chemical evidence for both rocky and icy bodies in an exoplanetary system and would be indicative of a planetary system so strongly perturbed that G238-44 is able to capture both asteroid- and Kuiper Belt-analog bodies near-simultaneously within its $<$100 Myr cooling age. Comment: Accepted to ApJ. 18 pages, 9 figures, 7 tables |
| Databáze: | arXiv |
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