Transiting White Dwarf Exoplanets with the Galactic Bulge Time Domain Survey

Transiting White Dwarf Exoplanets with the Galactic Bulge Time Domain Survey

Program ID	19060
Science Category	Exoplanets & Exoplanet Formation
Program Type	Analysis
Category	Small
Principal Investigator	Zifan Lin
PI Institution	Washington University
Co-Investigators	Tansu Daylan (Washington University)
Abstract	White dwarfs (WDs) present an unparalleled opportunity for the atmospheric characterization of exoplanets, as their small stellar radii yield exceptionally deep transits. However, the occurrence rate and post-main-sequence evolution of WD planetary systems remain poorly constrained due to a lack of deep, high-cadence photometric surveys. The Nancy Grace Roman Space Telescope's Galactic Bulge Time Domain Survey (GBTDS) provides a revolutionary dataset to resolve these fundamental demographic questions regarding planetary survival and system architecture. We propose a comprehensive archival investigation to systematically search for transiting WD exoplanets using GBTDS data. First, we will construct a robust target catalog expected to contain over 1,000 WDs within the survey footprint, combining Gaia DR3 astrometry with early Roman photometry to identify populations extending out to ~3 kpc. We will then develop a custom transit-search pipeline capable of producing sub-cadence light curves for bright targets to detect planetary companions. Demonstrating the feasibility of this approach, our comprehensive population synthesis and Pandeia photometric simulations confirm that while the crowded bulge environment dilutes target fluxes, the intrinsic depth of WD transits easily overcomes this blending effect. Roman will achieve high-confidence (>7-sigma) transit detections across a broad range of planetary radii, orbital periods, and host magnitudes. Ultimately, this program will deliver the first statistically robust constraints on WD exoplanet occurrence rates across Galactic distances, establishing the GBTDS as a transformative dataset for post-main-sequence exoplanet demography and identifying prime targets for future atmospheric characterization and the search for life elsewhere.