A Novel Approach to Identify Unseen Companions: An In-Depth study of GDR3 220_28
Abstract
Emission lines in the spectrum and the excess seen in the spectral energy distribution (SED) at infrared (IR) wavelengths serve as crucial indicators of accretion activity and the presence of gas and dust in the circumstellar environment of a young star. As accretion ceases over several million years, the Hα emission diminishes. However, IR excess combined with negligible Hα emission could also extend to indicate certain close binary systems, where a circumbinary disk contributes to the observed excess. Additionally, in unresolved binaries, companion stars can contribute to the photometry, leading to inaccuracies in parameter measurements and skewed positions in the color-magnitude diagram (CMD). We identify a photometrically peculiar object from a survey of the Cepheus star-forming regions (SFRs), Gaia DR3 2205212960562531328, exhibiting a shift from its expected position in the CMD, as indicated by the Gaia optical photometry. This peculiarity drives our research, prompting an investigation through an approach that combines astrometric accuracy, photometric modeling and spectroscopic studies. The Gaia XP spectrum of the source shows a systematic blue excess, indicating an additional hotter unresolved component. Two-component SED modelling yields a companion with Teff∼27000 K and log g≥4.5, consistent with sdB stars. Further CMD and spectroscopic analyses support a binary system consisting of an A0-type PMS star with an sdB companion. In addition, ZTF photometry shows tentative evidence for a periodicity of 0.498 days. This study paves the way for a systematic search of similar binary systems that would otherwise remain unidentified.
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BibTeX
@misc{cysil2026novel,
title = {{A Novel Approach to Identify Unseen Companions: An In-Depth study of GDR3 220_28}},
author = {T. B. Cysil and Blesson Mathew and B. Shridharan and S. Muneer and Pramod Kumar S and S. Nidhi and Sreeja S Kartha and Suman Bhattacharyya and T. Robin},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.09630},
eprint = {2610.09630},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.09630},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - A Novel Approach to Identify Unseen Companions: An In-Depth study of GDR3 220_28
AU - T. B. Cysil
AU - Blesson Mathew
AU - B. Shridharan
AU - S. Muneer
AU - Pramod Kumar S
AU - S. Nidhi
AU - Sreeja S Kartha
AU - Suman Bhattacharyya
AU - T. Robin
PY - 2026
DA - 2026/10/07
PB - arXiv
DO - 10.48550/arxiv.2610.09630
UR - https://arxiv.org/abs/2610.09630
AB - Emission lines in the spectrum and the excess seen in the spectral energy distribution (SED) at infrared (IR) wavelengths serve as crucial indicators of accretion activity and the presence of gas and dust in the circumstellar environment of a young star. As accretion ceases over several million years, the Hα emission diminishes. However, IR excess combined with negligible Hα emission could also extend to indicate certain close binary systems, where a circumbinary disk contributes to the observed excess. Additionally, in unresolved binaries, companion stars can contribute to the photometry, leading to inaccuracies in parameter measurements and skewed positions in the color-magnitude diagram (CMD). We identify a photometrically peculiar object from a survey of the Cepheus star-forming regions (SFRs), Gaia DR3 2205212960562531328, exhibiting a shift from its expected position in the CMD, as indicated by the Gaia optical photometry. This peculiarity drives our research, prompting an investigation through an approach that combines astrometric accuracy, photometric modeling and spectroscopic studies. The Gaia XP spectrum of the source shows a systematic blue excess, indicating an additional hotter unresolved component. Two-component SED modelling yields a companion with T_eff∼27000 K and log g≥4.5, consistent with sdB stars. Further CMD and spectroscopic analyses support a binary system consisting of an A0-type PMS star with an sdB companion. In addition, ZTF photometry shows tentative evidence for a periodicity of 0.498 days. This study paves the way for a systematic search of similar binary systems that would otherwise remain unidentified.
ER -