Detecting White Dwarf Exoplanets in the Roman Era
Abstract
White dwarfs (WDs) provide an unparalleled opportunity for detecting and characterizing exoplanets because of the large planet-to-star size ratio. However, only one transiting WD exoplanet is confirmed to date, and occurrence rate constraints remain loose because the rapid transits and weak phase curve modulations of WD exoplanets require high-precision, high-cadence photometry. The Galactic Bulge Time Domain Survey (GBTDS) of the Nancy Grace Roman Space Telescope will provide exactly this by observing thousands of WDs at 12.1-minute cadence. The expected WD exoplanet yield of this survey is not yet quantified. Here, we predict the GBTDS WD exoplanet yield over its first three high-cadence seasons, through both transiting and non-transiting (phase curve) channels. We run Monte Carlo detection probability simulations over a grid of planet radius, orbital period, and host properties for a Besançon synthetic population of WDs. Jupiter-sized planets dominate the transit yield, with a period-averaged effective survey size of N̅eff≈8, requiring an underlying occurrence rate of η̅1≈12% for one expected detection, followed by N̅eff≈2.6 (η̅1≈38%) for Neptune-sized and N̅eff≈1.8 (η̅1≈55%) for sub-Neptune-sized planets. Source blending is the major observational challenge in the crowded GBTDS fields, removing ≈95% of the raw predicted yield. Phase curve provides marginal detections, adding at most ≈4% to the transit yield. A null detection by GBTDS would constrain ηWD to < 28% for Jupiter-sized planets at 95% confidence. GBTDS will deliver the first WD exoplanet occurrence-rate constraints beyond the solar neighborhood and identify prime targets for future characterization.
Related
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- Detecting Exoplanetary Rings with Roman CGI Reflected Light Phase Curve Observations
- Detecting transiting exoplanets in simulated PLATO data: A comparison of light curve filter and transit search algorithms
- How dust particles orbiting white dwarfs can reveal undetected co-orbiting exoplanets II. Exoplanets on elliptic orbits
BibTeX
@misc{lin2026detecting,
title = {{Detecting White Dwarf Exoplanets in the Roman Era}},
author = {Zifan Lin and Tansu Daylan},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.09481},
eprint = {2609.09481},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.09481},
}
RIS
TY - UNPB
TI - Detecting White Dwarf Exoplanets in the Roman Era
AU - Zifan Lin
AU - Tansu Daylan
PY - 2026
DA - 2026/09/08
PB - arXiv
DO - 10.48550/arxiv.2609.09481
UR - https://arxiv.org/abs/2609.09481
AB - White dwarfs (WDs) provide an unparalleled opportunity for detecting and characterizing exoplanets because of the large planet-to-star size ratio. However, only one transiting WD exoplanet is confirmed to date, and occurrence rate constraints remain loose because the rapid transits and weak phase curve modulations of WD exoplanets require high-precision, high-cadence photometry. The Galactic Bulge Time Domain Survey (GBTDS) of the Nancy Grace Roman Space Telescope will provide exactly this by observing thousands of WDs at 12.1-minute cadence. The expected WD exoplanet yield of this survey is not yet quantified. Here, we predict the GBTDS WD exoplanet yield over its first three high-cadence seasons, through both transiting and non-transiting (phase curve) channels. We run Monte Carlo detection probability simulations over a grid of planet radius, orbital period, and host properties for a Besançon synthetic population of WDs. Jupiter-sized planets dominate the transit yield, with a period-averaged effective survey size of N̅_eff≈8, requiring an underlying occurrence rate of η̅_1≈12% for one expected detection, followed by N̅_eff≈2.6 (η̅_1≈38%) for Neptune-sized and N̅_eff≈1.8 (η̅_1≈55%) for sub-Neptune-sized planets. Source blending is the major observational challenge in the crowded GBTDS fields, removing ≈95% of the raw predicted yield. Phase curve provides marginal detections, adding at most ≈4% to the transit yield. A null detection by GBTDS would constrain η_WD to < 28% for Jupiter-sized planets at 95% confidence. GBTDS will deliver the first WD exoplanet occurrence-rate constraints beyond the solar neighborhood and identify prime targets for future characterization.
ER -