Now Reading: Do White Dwarfs Sample Water-Rich Planetary Material?
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Do White Dwarfs Sample Water-Rich Planetary Material?
The distribution of accretion parameters relative to steady state derived from the posteriors of the MCMC tests, separated based on the dominant atmospheric species. To compare accretion phases, we have recast τd as tSS according to Equation 2. Solutions to the left of the vertical line correspond with the mass-buildup phase while the right is generally the mass-settling phase for the He-WDs and typically samples the steady-state for H-WDs. Most of the individual white dwarfs peak around steady state, and have broad distributions. “Weighted” refers to applying a likelihood function that prefers solutions that maximize the mass of pollution in the atmosphere. “Restricted τd” curves place a restricted prior on the disk lifetime of 104 − 107 yr, while non-restricted curves allow τd to vary freely between 10−6 to 1010 yr. Applying a weighted likelihood function to prefer solutions that maximize the mass currently in the atmosphere of the white dwarf tends to bring solutions towards the steady state and mass-buildup phases. H-WDs tend to peak at relatively later accretion parameters than He-WDs but for relevant settling timescales still easily reside in the steady state. — astro-ph.EP
Polluted white dwarfs offer a unique way to directly probe the compositions of exoplanetary bodies.
We examine the water content of accreted material using the oxygen abundances of 51 highly polluted white dwarfs. Within this sample, we present new abundances for three H-dominated atmosphere white dwarfs that showed promise for accreting water-rich material.
Throughout, we explore the impact of the observed phase and lifetime of accretion disks on the inferred elemental abundances of the parent bodies that pollute each white dwarf. Our results indicate that white dwarfs sample a range of dry to water-rich material, with median uncertainties in water mass fractions of ≈15%.
Amongst the He-dominated white dwarfs, 35/39 water abundances are consistent with corresponding H abundances. While for any individual white dwarf it may be ambiguous as to whether or not water is present in the accreted parent body, when considered as a population the prevalence of water-rich bodies is statistically robust.
The population as a whole has a median water mass fraction of ≈25%, and enforcing chondritic parent body compositions, we find that 31/51 WDs are likely to have non-zero water concentrations. This conclusion is different from a similar previous analysis of white dwarf pollution and we discuss reasons why this might be the case.
Pollution in H-dominated white dwarfs continues to be more water-poor than in their He-dominated cousins, although the sample size of H-dominated white dwarfs remains small and the two samples still suffer a disjunction in the range of host star temperatures being probed.
Isabella L. Trierweiler, Carl Melis, Érika Le Bourdais, Patrick Dufour, Alycia J. Weinberger, Boris T. Gänsicke, Nicola Gentile-Fusillo, Siyi Xu, Jay Farihi, Andrew Swan, Malena Rice, Edward D. Young
Comments: 30 pages, 14 figures Accepted to ApJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2508.20172 [astro-ph.EP] (or arXiv:2508.20172v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2508.20172
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Submission history
From: Isabella Trierweiler
[v1] Wed, 27 Aug 2025 18:00:07 UTC (1,655 KB)
https://arxiv.org/abs/2508.20172
Astrobiology
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