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arXiv · 2509.06910

Revealing Unresolved White Dwarf-Main Sequence Binaries using Gaia DR3 and GALEX I. A Volume limited study of 100 pc

Prasanta K. Nayak
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Abstract

Context. Understanding the demographics of white dwarf - main sequence (WDMS) binaries is key to uncovering the formation of various stellar exotica and refining the details of binary stellar evolution. Despite several dedicated efforts to identify unresolved WDMS binaries, their population remains incomplete, even within a 100 pc volume-limited sample. Aims. This study aims to identify WDMS binaries hidden within the main sequence of the optical color-magnitude diagram (CMD), improving the completeness of WDMS binaries within a volume-limited sample of 100 pc. Methods. We use NUV-optical CMDs to distinguish unresolved WDMS binaries from the rest of the populations. High-precision astrometric and photometric data from Gaia DR3 and NUV data from GALEX GR6/7 are combined to construct CMDs. Using the binary spectral energy distribution (SED) fitting algorithm within the Virtual Observatory SED Analyzer (VOSA) tool, we estimate stellar parameters such as effective temperature, bolometric luminosity, and radii. The masses of the WD companions are determined using white dwarf evolutionary models. As we use the sources which are detected only in NUV band of GALEX, this study directly complements to majority of the previous studies. Results. We identify 596 WD-MS binary candidates within 100 pc, with 497 newly reported. Our method predominantly identifies binaries with cooler WD companions (median ~7,000 K) compared to previous studies. The WD masses range from ~0.2 and 1.3 M$_\odot$, and most MS companions are of M spectral type.

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Prasanta K. Nayak. 2026-04-02. Revealing Unresolved White Dwarf-Main Sequence Binaries using Gaia DR3 and GALEX I. A Volume limited study of 100 pc. https://doi.org/10.1051/0004-6361%2F202452939

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