Gaia DR3 detectability of unresolved binary systems
Astronomy & Astrophysics(2024)
摘要
Gaia can not individually resolve very close binary systems, however, the
collected data can still be used to identify them. A powerful indicator of
stellar multiplicity is the sources reported Renormalized Unit Weight Error
(ruwe), which effectively captures the astrometric deviations from
single-source solutions. We aim to characterise the imprints left on ruwe
caused by binarity. By flagging potential binary systems based on ruwe, we aim
to characterise which of their properties will contribute the most to their
detectability. We develop a model to estimate ruwe values for observations of
Gaia sources, based on the biases to the single-source astrometric track
arising from the presence of an unseen companion. Then, using the recipes from
previous GaiaUnlimited selection functions, we estimate the selection
probability of sources with high ruwe, and discuss what binary properties
contribute to increasing the sources ruwe. We compute the maximum ruwe value
which is compatible with single-source solutions as a function of their
location on-sky. We see that binary systems selected as sources with a ruwe
higher than this sky-varying threshold have a strong detectability window in
their orbital period distribution, which peaks at periods equal to the Gaia
observation time baseline. We demonstrate how our sky-varying ruwe threshold
provides a more complete sample of binary systems when compared to single
sky-averaged values by studying the unresolved binary population in the Gaia
Catalogue of Nearby Stars. We provide the code and tools used in this study, as
well as the sky-varying ruwe threshold through the GaiaUnlimited Python package
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