Table 1.
Published binary fractions for HB stars.
| Population | Binary Fraction | Method | Metallicity [Fe/H] | Reference |
|---|---|---|---|---|
| BHB | < 2.2% | RV | −1.7 ± 0.3 | (this work) |
| BHB (halo GC)1 | 5 − 10% | RV | −1.1 | Moni Bidin et al. (2011) |
| BHB (halo field)2 | ≲5% | RV | – | Green et al. (2014) |
| BHB (halo)3 | 29 ± 3% | RV | > − 1.5 | Guo et al. (2025) |
| EHB (field) | ∼50% | RV + light curves | −1.5 to +0.2 | Geier et al. (2022) |
| RR Lyrae (halo) | < 3%* | Gaia + RV | −1.5 to +0.2 | Bobrick et al. (2024) |
| RHB | undetermined | – | – | – |
| Red Clump (field) | ∼20% | APOGEE RV | −0.5 to +0.5 | Badenes et al. (2018) |
Notes. 1 Based on 14 epochs of RV data acquired over 75 days for 64 stars. 2 Based on > 5 epochs of RV data acquired over 2 years for 8 stars. 3 Based on > 2 epochs of LAMOST low resolution spectra for 299 stars. * Based on 500 candidates from 17 570 catalogue RR Lyr with full light curve information.
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