2026ApJ...996...69M

The initial-final mass relation (IFMR) links a star's birth mass to the mass of its white dwarf (WD) remnant, providing key constraints on stellar evolution. Open clusters offer the most straightforward way to empirically determine the IFMR, as their well-defined ages allow for direct progenitor lifetime estimates. We construct the most comprehensive open cluster WD IFMR to date by combining new spectroscopy of 22 WDs with an extensive literature review of WDs with strong cluster associations. To minimize systematics, we restrict our analysis to spectroscopically confirmed hydrogen-atmosphere (DA) WDs consistent with single-stellar origins. We separately analyze a subset with reliable Gaia-based astrometric membership assessments, as well as a full sample that adds WDs with strong cluster associations whose membership cannot be reliably assessed with Gaia. The Gaia-based sample includes 69 spectroscopically confirmed DA WDs, more than doubling the sample size of previous Gaia-based open cluster IFMRs. The full sample, which includes 53 additional literature WDs, increases the total number of cluster WDs by over 50% relative to earlier works. We provide functional forms for both the Gaia-based and full-sample IFMRs. The Gaia-based result useful for M_i ≥ 2.67 M_⊙ is ${M}_{f}=\left[0.179-0.100H({M}_{i}-3.84\,{M}_{\odot })\right]\times ({M}_{i}-3.84\,{M}_{\odot })+0.628\,{M}_{\odot }$, where H(x) is the Heaviside step function. Comparing our IFMR to recent literature, we identify significant deviations from best-fit IFMRs derived from both Gaia-based volume-limited samples of field WDs and double WD binaries, with the largest discrepancy occurring for initial masses of about 5 M_⊙.