Discovery of a second-generation planet candidate accreting onto a white dwarf
Abstract
Many white dwarfs accrete the debris of disrupted planetary bodies, detected in the form of metal-enrichment in their atmospheres, dusty or gaseous circumstellar discs, and photometric transits from debris. The composition of accreted debris has been shown to be diverse yet overall closely resembles Solar System bodies. We report the discovery of a white dwarf accreting material that is unlike any Solar System object. The atmosphere of HS 0209+0832 is strongly enriched in trans-iron elements including zinc, copper, and niobium but depleted in the canonical rock-forming elements silicon and iron. The composition of the accreted object is consistent with a candidate second-generation planet, formed from the stellar material ejected during the giant phase. The key abundance signature which differentiates it from a first-generation planet is the high enrichment of s-process elements. Photospheric helium and the absence of terrestrial rock-forming elements implies the white dwarf is accreting from the escaped atmosphere of a photo-evaporating giant planet candidate. This is further supported by the detection of a sinusoidal photometric period of 4.399+/-0.026 days at an amplitude of 0.120+/-0.018 %, which we attribute to thermal emission phase variability from a planetary day-night cycle or a transiting cometary tail of an evaporating gas giant.
Versions
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BibTeX
@misc{williams2026discovery,
title = {{Discovery of a second-generation planet candidate accreting onto a white dwarf}},
author = {Jamie T. Williams and Boris T. Gänsicke and Nicholas C. Stone and Detlev Koester and Benjamin D. R. Davies and Christopher Tong and David J. Wilson and Snehalata Sahu and Andrew Swan and Thomas G. Beatty and Sergio H. Ramírez and Tim Cunningham and Knox S. Long},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.07161},
eprint = {2610.07161},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.07161},
}
RIS
TY - UNPB
TI - Discovery of a second-generation planet candidate accreting onto a white dwarf
AU - Jamie T. Williams
AU - Boris T. Gänsicke
AU - Nicholas C. Stone
AU - Detlev Koester
AU - Benjamin D. R. Davies
AU - Christopher Tong
AU - David J. Wilson
AU - Snehalata Sahu
AU - Andrew Swan
AU - Thomas G. Beatty
AU - Sergio H. Ramírez
AU - Tim Cunningham
AU - Knox S. Long
PY - 2026
DA - 2026/10/05
PB - arXiv
DO - 10.48550/arxiv.2610.07161
UR - https://arxiv.org/abs/2610.07161
AB - Many white dwarfs accrete the debris of disrupted planetary bodies, detected in the form of metal-enrichment in their atmospheres, dusty or gaseous circumstellar discs, and photometric transits from debris. The composition of accreted debris has been shown to be diverse yet overall closely resembles Solar System bodies. We report the discovery of a white dwarf accreting material that is unlike any Solar System object. The atmosphere of HS 0209+0832 is strongly enriched in trans-iron elements including zinc, copper, and niobium but depleted in the canonical rock-forming elements silicon and iron. The composition of the accreted object is consistent with a candidate second-generation planet, formed from the stellar material ejected during the giant phase. The key abundance signature which differentiates it from a first-generation planet is the high enrichment of s-process elements. Photospheric helium and the absence of terrestrial rock-forming elements implies the white dwarf is accreting from the escaped atmosphere of a photo-evaporating giant planet candidate. This is further supported by the detection of a sinusoidal photometric period of 4.399+/-0.026 days at an amplitude of 0.120+/-0.018 %, which we attribute to thermal emission phase variability from a planetary day-night cycle or a transiting cometary tail of an evaporating gas giant.
ER -