Atypical White Dwarfs in Open Clusters
Abstract
Open clusters are powerful laboratories for investigating the formation and evolution of white dwarfs (WDs), as their well-constrained ages link WDs to their progenitor stars. This is particularly valuable for atypical WDs, including magnetic WDs and those with non-hydrogen-dominated spectra, whose origins can be difficult to disentangle in the field. We assemble the largest sample to date of atypical WDs in open clusters: eight non-magnetic WDs with helium-dominated spectra, five with featureless spectra, and five magnetic WDs showing hydrogen or helium lines. We find no significant difference between the initial--final mass relations of hydrogen- and helium-atmosphere WDs, nor robust spatial or kinematic differences. The strongest difference from the field is a deficit of non-DAs between $0.8$ and 1.0 M⊙, where the field predicts 6.0+0.8−0.7 WDs, yet none are observed, with a probability of only 0.37%. Massive magnetic WDs show a similar deficit: only one of 20 cluster WDs with MWD≥1.0 M⊙ and Teff≥20,000 K is magnetic, compared with 10 of 16 in the field. Together, these deficits are consistent with an additional field population of massive merger remnants, particularly high-mass magnetic WDs and warm/hot DQs. Such objects may be underrepresented in clusters because young systems provide limited time for certain classes of delayed mergers, while older clusters lose members or dissolve; the field accumulates binary evolution products over Galactic timescales. Magnetic cluster WDs consistent with single-star evolution further suggest mass-dependent magnetic-field emergence, with fields appearing early in some massive WDs while young lower-mass WDs remain consistent with delayed emergence.
Related
- Evolution of Stellar Activity and Habitable Zone (EATEN): III. X-ray Activity of Dwarfs in Open Clusters and Field Stars
- Evolution of Stellar Activity and Habitable Zone. III. X-Ray Activity of Dwarfs in Open Clusters and Field Stars
- Evolution of Stellar Activity and Habitable Zone. IV. Calcium II Infrared Triplet Activity from Open Clusters and White Dwarf Binaries
- The white dwarf population of open clusters and their tidal tails. Tracers of contamination and stellar interactions
- Temperature effects on white dwarfs in modified gravity
BibTeX
@misc{miller2026atypical,
title = {{Atypical White Dwarfs in Open Clusters}},
author = {David R. Miller and Ilaria Caiazzo and Jeremy Heyl and Pier-Emmanuel Tremblay},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.10699},
eprint = {2610.10699},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.10699},
}
RIS
TY - UNPB
TI - Atypical White Dwarfs in Open Clusters
AU - David R. Miller
AU - Ilaria Caiazzo
AU - Jeremy Heyl
AU - Pier-Emmanuel Tremblay
PY - 2026
DA - 2026/10/07
PB - arXiv
DO - 10.48550/arxiv.2610.10699
UR - https://arxiv.org/abs/2610.10699
AB - Open clusters are powerful laboratories for investigating the formation and evolution of white dwarfs (WDs), as their well-constrained ages link WDs to their progenitor stars. This is particularly valuable for atypical WDs, including magnetic WDs and those with non-hydrogen-dominated spectra, whose origins can be difficult to disentangle in the field. We assemble the largest sample to date of atypical WDs in open clusters: eight non-magnetic WDs with helium-dominated spectra, five with featureless spectra, and five magnetic WDs showing hydrogen or helium lines. We find no significant difference between the initial--final mass relations of hydrogen- and helium-atmosphere WDs, nor robust spatial or kinematic differences. The strongest difference from the field is a deficit of non-DAs between $0.8$ and 1.0 M_⊙, where the field predicts 6.0^+0.8_−0.7 WDs, yet none are observed, with a probability of only 0.37%. Massive magnetic WDs show a similar deficit: only one of 20 cluster WDs with M_WD≥1.0 M_⊙ and T_eff≥20,000 K is magnetic, compared with 10 of 16 in the field. Together, these deficits are consistent with an additional field population of massive merger remnants, particularly high-mass magnetic WDs and warm/hot DQs. Such objects may be underrepresented in clusters because young systems provide limited time for certain classes of delayed mergers, while older clusters lose members or dissolve; the field accumulates binary evolution products over Galactic timescales. Magnetic cluster WDs consistent with single-star evolution further suggest mass-dependent magnetic-field emergence, with fields appearing early in some massive WDs while young lower-mass WDs remain consistent with delayed emergence.
ER -