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ABSTRACT The third data release of Gaia was the first to include orbital solutions assuming non-single stars. Here, we apply the astrometric triage technique of Shahaf et al. to identify binary star systems with companions that are not single main-sequence stars. Gaia’s synthetic photometry of these binaries is used to distinguish between systems likely to have white-dwarf companions and those that may be hierarchical triples. The study uncovered a population of nearly $$3\, 200$$ binaries, characterized by orbital separations on the order of an astronomical unit, in which the faint astrometric companion is probably a white dwarf. This sample increases the number of orbitally solved binary systems of this type by about two orders of magnitude. Remarkably, over 110 of these systems exhibit significant ultraviolet excess flux, confirming this classification and, in some cases, indicating their relatively young cooling ages. We show that the sample is not currently represented in synthetic binary populations, and is not easily reproduced by available binary population synthesis codes. Therefore, it challenges current binary evolution models, offering a unique opportunity to gain insights into the processes governing white-dwarf formation, binary evolution, and mass transfer.
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This content will become publicly available on December 23, 2025
Moderate-separation Binary Companions May Influence Young Stellar X-Ray Luminosity
Abstract Young pre-main sequence stars exhibit elevated X-ray levels due to their strong magnetic activity. Understanding young stars’ X-ray activity is essential for contextualizing the forming planets that they host. Binary stars present a unique environment that may influence planet formation and evolution. In this work, we assembled a sample of 65 systems with stellar characterization from the literature and X-ray fluxes from the XMM-Newton Extended Survey of the Taurus Molecular Cloud to investigate the potential relationship between binary separation and X-ray flux. We found that binary stars with separations smaller than the sample median may exhibit elevated X-ray flux compared to single stars. This suggests that binary companions could influence stellar and planetary evolution and warrants further investigation.
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- Award ID(s):
- 2150255
- PAR ID:
- 10629477
- Publisher / Repository:
- RNAAS
- Date Published:
- Journal Name:
- Research Notes of the AAS
- Volume:
- 8
- Issue:
- 12
- ISSN:
- 2515-5172
- Page Range / eLocation ID:
- 318
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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