Resolving the Unresolved: Using NESSI to Search for Unresolved Companions in Low-mass Disk Wide Binaries

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Main Authors: Hartman, Zachary D., van Belle, Gerard, Lépine, Sébastien, Everett, Mark E., Medan, Ilija
Format: Preprint
Published: 2025
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author Hartman, Zachary D.
van Belle, Gerard
Lépine, Sébastien
Everett, Mark E.
Medan, Ilija
author_facet Hartman, Zachary D.
van Belle, Gerard
Lépine, Sébastien
Everett, Mark E.
Medan, Ilija
contents Stellar systems consisting of three or more stars are not an uncommon occurrence in the Galaxy. Nearly 50% of solar-type wide binaries with separations >1000 au are actually higher-order multiples with one component being a close binary. Additionally, the higher-order multiplicity fraction appears to be correlated with the physical separation of the widest component. These facts have motivated some of our current theories behind how the widest stellar systems formed, which can have separations on the order of or larger than protostellar cores. However, it is unclear if the correlation between wide binary separation and higher-order multiplicity extends to low-mass binaries. We present initial results of an ongoing speckle imaging survey of nearby low-mass wide binaries. We find an overall higher-order multiplicity fraction for our sample of $42.0\% \pm 10.9\%$. If we include systems where Gaia indicates that a companion is likely present, this fraction increases to $62.0\% \pm 14.2\%$. This is consistent with previous results from both higher-mass stars and a previous result for low-mass wide binaries. However, we do not detect the expected increase in higher-order multiplicity fraction with separation, as was seen with previous studies. We briefly explore why higher-order multiplicity statistics could be different in low-mass stars, and what the significance might be for models of wide binary formation.
format Preprint
id arxiv_https___arxiv_org_abs_2506_07499
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Resolving the Unresolved: Using NESSI to Search for Unresolved Companions in Low-mass Disk Wide Binaries
Hartman, Zachary D.
van Belle, Gerard
Lépine, Sébastien
Everett, Mark E.
Medan, Ilija
Solar and Stellar Astrophysics
Stellar systems consisting of three or more stars are not an uncommon occurrence in the Galaxy. Nearly 50% of solar-type wide binaries with separations >1000 au are actually higher-order multiples with one component being a close binary. Additionally, the higher-order multiplicity fraction appears to be correlated with the physical separation of the widest component. These facts have motivated some of our current theories behind how the widest stellar systems formed, which can have separations on the order of or larger than protostellar cores. However, it is unclear if the correlation between wide binary separation and higher-order multiplicity extends to low-mass binaries. We present initial results of an ongoing speckle imaging survey of nearby low-mass wide binaries. We find an overall higher-order multiplicity fraction for our sample of $42.0\% \pm 10.9\%$. If we include systems where Gaia indicates that a companion is likely present, this fraction increases to $62.0\% \pm 14.2\%$. This is consistent with previous results from both higher-mass stars and a previous result for low-mass wide binaries. However, we do not detect the expected increase in higher-order multiplicity fraction with separation, as was seen with previous studies. We briefly explore why higher-order multiplicity statistics could be different in low-mass stars, and what the significance might be for models of wide binary formation.
title Resolving the Unresolved: Using NESSI to Search for Unresolved Companions in Low-mass Disk Wide Binaries
topic Solar and Stellar Astrophysics
url https://arxiv.org/abs/2506.07499