Two related studies use Gaia DR3 (including the Focused Product Release) to evaluate how well symbiotic binaries are represented and to search for additional systems. Symbiotic stars are long-period binaries consisting of an evolved giant and a hot compact companion, often producing complex spectra and strong emission features. In the first work, the authors cross-match confirmed symbiotic stars with Gaia DR3 and FPR data and find that astrometric information is generally reliable for locating symbiotics in the color–magnitude diagram. They report that RUWE is not a dependable indicator of binarity for this class, and that most systems show variability in Gaia photometry. Mean and epoch radial velocities and inferred orbital solutions are broadly consistent with published literature; tentative orbital solutions are provided for two sources. However, derived effective temperatures and metallicities are often unreliable due to contamination from nebular continuum and strong emission lines, while Hα emission is detected in nearly all symbiotics and serves as a robust diagnostic. In the second work, the authors test Gaia DR3’s general variability classification for symbiotic candidates, train a Random Forest classifier to estimate contamination, and conclude that most candidates overlap with pulsating red giants. Follow-up spectroscopy confirms three new symbiotic stars, with eight strong remaining candidates among the newly proposed objects.
Gaia DR3 studies identify symbiotic stars and isolate a small set of new candidates
Two related studies use Gaia DR3 (including the Focused Product Release) to evaluate how well symbiotic binaries are represented and to search for additional systems. Symbiotic stars are long-period b...
- Gaia DR3 reliably places known symbiotic stars in the color–magnitude diagram using astrometric data.
- RUWE is generally not a reliable binarity indicator for symbiotic binaries.
- Most symbiotic systems show variability in Gaia photometry, and Hα emission is detected in nearly all symbiotics.
- Effective temperatures and metallicities from Gaia-derived products are often unreliable due to contamination from nebular continuum and emission lines.
- From 339 newly proposed Gaia variability-based candidates, follow-up spectroscopy confirms three new symbiotic stars, leaving eight strong candidates; many others are likely contaminants such as pulsating red giants.
arXiv:2607.12690v1 Announce Type: new Abstract: Symbiotic stars are long-period interacting binaries composed of an evolved giant and a hot compact companion. Their complex spectra and variability make them both astrophysically valuable and observationally challenging. We investigate how known symbiotic stars are represented in Gaia DR3 and the Focused Product Release (FPR), assess the reliability of these data, and evaluate their usefulness for candidate analysis and searches for new systems. We crossmatched Gaia DR3 and the FPR with confirmed symbiotic stars from the New Online Database of Symbiotic Variables and examined their astrometric, photometric, and spectroscopic data, along with derived products such as astrophysical parameters, orbital solutions, variability properties, and emission-line classifications. Astrometric data reliably constrain the position of symbiotics in the color-magnitude diagram, aiding searches for new systems, while RUWE is generally not a reliable indicator of their binarity. Most symbiotics are variable in Gaia photometry. Mean and epoch radial velocities, as well as inferred orbital solutions, are broadly consistent with the literature, and we provide the first tentative orbital solutions for two systems. Effective temperatures and metallicities are unreliable due to contamination from nebular continuum and strong emission lines. H$\alpha$ emission is detected in nearly all symbiotics, making it a robust diagnostic. Additionally, resolved companions were identified for two systems, and one previously confirmed symbiotic star was reclassified as non-symbiotic. Gaia DR3 provides a rich dataset for the study of symbiotic binaries. The forthcoming DR4 promises a major leap forward with its longer time baseline, new data products, and epoch data.
2 hours agoarXiv:2607.12699v1 Announce Type: new Abstract: We investigate the reliability of the symbiotic star class in the general variability classification of Gaia DR3 and search for new genuine symbiotic systems among the objects assigned to this category. The sample contains 649 sources, including 246 previously known symbiotic stars, 61 literature candidates, and 339 new candidates proposed by the Gaia variability pipeline. Diagnostics based on the Gaia colour-magnitude diagram, near-infrared photometry, and the pseudo-equivalent width of H$\alpha$ indicate that a large fraction of the new candidates are likely contaminants, predominantly pulsating red giants. To quantify the contamination, we constructed a Random Forest classifier trained on confirmed symbiotic stars and on Mira and semi-regular variables, using Gaia photometry, variability parameters, H$\alpha$ measurements from XP spectra, and infrared colours. The classifier reaches a balanced accuracy of $\approx$0.94 and efficiently separates most symbiotic binaries from single evolved stars, leaving only eight strong candidates among the 339 newly proposed objects. Follow-up spectroscopy confirms three new symbiotic stars through the presence of high-excitation emission lines, while several additional objects remain possible symbiotics. Our results show that the Gaia DR3 variability classification efficiently recovers known symbiotic stars but has low purity due to overlap with pulsating red giants. The small number of newly confirmed systems implies that the discrepancy between predicted and observed Galactic symbiotic populations remains unresolved, although Gaia provides a powerful basis for future searches combining variability, spectroscopic indicators, and multi-wavelength data.
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