Constraining the Merger Fraction and the Upper Mass Limit of Ultramassive White Dwarfs
Abstract
We performed a spectroscopic survey of all known white dwarfs with M ≥ 1.3 M⊙ and Teff≥11,000 K identified through Gaia DR3 astrometry from the Gentile-Fusillo et al. (2021) catalog. Of the 293 white dwarf candidates that met our criteria, 259 had no optical spectroscopy or spectral classification available in the literature. We obtained follow-up spectroscopy on 97% of this sample and performed a detailed model atmosphere analysis to constrain the atmospheric composition and mass for each object. For a selection of magnetic white dwarfs, we use offset dipole models to constrain the magnetic field strength and geometry and calculate the magnetic fraction as a function of mass. We use magnetism, unusual atmospheric composition, kinematics, and rapid rotation rates to identify merger remnants, and constrain the merger fraction to be 53−6+7% for white dwarfs more massive than 1.3 M⊙. Hence, roughly half of the most massive white dwarfs likely form through binary mergers. We also use our sample to derive an empirical upper mass limit for white dwarfs in the solar neighborhood. Including the General Relativistic effects, the most massive white dwarf in our sample, J0318+7923, has M=1.33−1.35 M⊙ depending on the unknown core composition. Furthermore, because our temperature criteria overlap with the ZZ Ceti instability strip, we find a new selection of ultramassive pulsator candidates that may provide an excellent opportunity to probe the interiors of crystallized CO or ONe-core white dwarfs.
Related
- Debye cooling of ultramassive white dwarfs
- Eight New Ultramassive Black Hole Masses Confirm Best Correlation with Galaxy Core Sizes
- The JWST Ultramassive Galaxy Sample -- II. Supermassive Black Hole Masses for 8 Extreme Early-Type Galaxies via Jeans Anisotropic Modelling of High-Resolution Integral-Field NIRSpec Stellar Kinematics
- The JWST Ultramassive Galaxy Sample -- I. Overview, Photometry, and Stellar Kinematics: Selecting Optimal Template Subsets via Non-Negative Matrix Factorization
- Stochastic black hole growth tracks stellar mass in ultramassive galaxies
BibTeX
@misc{jewett2026constraining,
title = {{Constraining the Merger Fraction and the Upper Mass Limit of Ultramassive White Dwarfs}},
author = {Gracyn Jewett and Mukremin Kilic and Pierre Bergeron and Alex Gleason and Warren R. Brown and Manuel Barrientos and Matthew J. Green and Simon Blouin and Vikram S. Dhillon and Stuart Littlefair},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.08736},
eprint = {2611.08736},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.08736},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Constraining the Merger Fraction and the Upper Mass Limit of Ultramassive White Dwarfs
AU - Gracyn Jewett
AU - Mukremin Kilic
AU - Pierre Bergeron
AU - Alex Gleason
AU - Warren R. Brown
AU - Manuel Barrientos
AU - Matthew J. Green
AU - Simon Blouin
AU - Vikram S. Dhillon
AU - Stuart Littlefair
PY - 2026
DA - 2026/11/05
PB - arXiv
DO - 10.48550/arxiv.2611.08736
UR - https://arxiv.org/abs/2611.08736
AB - We performed a spectroscopic survey of all known white dwarfs with M ≥ 1.3 M_⊙ and T_eff≥11,000 K identified through Gaia DR3 astrometry from the Gentile-Fusillo et al. (2021) catalog. Of the 293 white dwarf candidates that met our criteria, 259 had no optical spectroscopy or spectral classification available in the literature. We obtained follow-up spectroscopy on 97% of this sample and performed a detailed model atmosphere analysis to constrain the atmospheric composition and mass for each object. For a selection of magnetic white dwarfs, we use offset dipole models to constrain the magnetic field strength and geometry and calculate the magnetic fraction as a function of mass. We use magnetism, unusual atmospheric composition, kinematics, and rapid rotation rates to identify merger remnants, and constrain the merger fraction to be 53_−6^+7% for white dwarfs more massive than 1.3 M_⊙. Hence, roughly half of the most massive white dwarfs likely form through binary mergers. We also use our sample to derive an empirical upper mass limit for white dwarfs in the solar neighborhood. Including the General Relativistic effects, the most massive white dwarf in our sample, J0318+7923, has M=1.33−1.35 M_⊙ depending on the unknown core composition. Furthermore, because our temperature criteria overlap with the ZZ Ceti instability strip, we find a new selection of ultramassive pulsator candidates that may provide an excellent opportunity to probe the interiors of crystallized CO or ONe-core white dwarfs.
ER -