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arXiv · 2607.06357

White dwarfs within 13 pc: insights from ultraviolet spectroscopy

Mairi W. O'Brien·Pier-Emmanuel Tremblay·Boris T. Gänsicke·Mark A. Hollands·Detlev Koester·Snehalata Sahu·Antoine Bédard·Andrew M. Buchan·Tim Cunningham·John H. Debes·Jay Farihi·J. J. Hermes·Piotr M. Kowalski
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Abstract

We present a comprehensive multi-wavelength spectroscopic and photometric analysis of the 44 confirmed white dwarfs within 13 pc of the Sun. Combining flux-calibrated ultraviolet spectroscopy from the Hubble Space Telescope (STIS and COS) with ground-based optical spectroscopy, as well as photometry from Gaia, 2MASS, and WISE, we employ a combined fitting method to calculate atmospheric parameters. Each white dwarf is fitted with a bespoke model depending on its detailed atmospheric composition. Two strongly magnetic stars could not be fitted due to the complex splitting of their spectral lines. We find a systematic discrepancy in hydrogen-atmosphere white dwarfs with effective temperatures below 10,000K, where fits incorporating ultraviolet spectra result in effective temperatures that are 1 - 5 per cent higher than those derived from optical and infrared photometry alone. We re-classify three helium-atmosphere white dwarfs as metal enriched following a magnesium detection in their near-ultraviolet spectra: WD 0435-088, WD 1132-325 and WD 1917+386. In total, we identify five stars in the sample for which metals are only detected in the ultraviolet. Overall, we find that 30 per cent of the 13 pc white dwarfs show spectroscopic evidence of evolved planetary systems. Our analysis reveals no measurable difference between the hydrogen content of DQ and DC white dwarfs, although the upper limits of carbon in DCs are significantly below that of the DQ population. We find a multiplicity fraction of 33 per cent for the 13 pc white dwarfs.

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Mairi W. O'Brien, Pier-Emmanuel Tremblay, Boris T. Gänsicke, Mark A. Hollands, Detlev Koester, Snehalata Sahu, Antoine Bédard, Andrew M. Buchan, Tim Cunningham, John H. Debes, Jay Farihi, J. J. Hermes, Piotr M. Kowalski. 2026-07-07. White dwarfs within 13 pc: insights from ultraviolet spectroscopy. https://arxiv.org/abs/2607.06357

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