ner_tags: O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O B-Survey O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Survey O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Survey B-Citation I-Citation I-Citation I-Citation O O B-Telescope B-Citation I-Citation I-Citation I-Citation O O O O O O O O O B-Telescope O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Telescope B-Dataset O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O B-Telescope O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O B-Telescope O O B-Citation I-Citation I-Citation O O O B-Telescope O O O O O O O O O O O O O B-Wavelength O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O B-Wavelength O O O O O B-Telescope O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O B-Telescope O O O O O O O O O O O O O O O O O O O O O O B-Wavelength I-Wavelength O B-Wavelength I-Wavelength O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O
tokens: confidently identify these periodic variations. Price-Whelan et al. ( 2020b ) identified 19 635 candidate binaries in the APOGEE survey based on radial velocity variations between multiple observations. Of these, 53 are in our giant star data set, including 15 of our RC stars – one of which is Li-rich. It has only three observations with APOGEE, indicating an RV range of . In terms of photometric signatures of binarity in the form of transits, assuming random orbital inclinations and observed orbital period distributions (e.g. Raghavan et al. 2010 ), 2.5 ± 0.5 per cent of our Li-rich RC stars should be in eclipsing binary systems. The secondary star will block about 1 per cent of the disc of the primary with an eclipse period of ∼3 d. This does not require a very high cadence in photometric monitoring, but none of our Li-rich RC stars have so far had light curves in ASAS-SN (Kochanek et al. 2017 ) or TESS (Ricker et al. 2014 ) that show evidence for eclipses. The astrometry from Gaia is precise enough to measure the motion of the photocentre of some binary systems (depending on heliocentric distance and the binary properties). The model assumption underlying the data processing for Gaia DR2 is that sources are single objects, and if there are photocentre shifts in binary systems these are interpreted as larger than expected astrometric errors. Work by Penoyre et al. ( 2020 ) and Belokurov et al. ( 2020 ) have used large values of the Renormalized Unit Weight Error ( RUWE ), an astrometric error metric reported by Gaia , to identify possible binaries. Our data set excludes stars with large RUWE by construction (it is part of flag_sp ), because parallax is an important prior in our stellar parameter determination. 3.5 Infrared excess A fraction of Li-rich RGB stars have been reported to have excess flux in their spectral energy distribution in the IR, which has been postulated as a sign of a physical connection between lithium production and mass-loss. This can be seen in photometry from the IRAS satellite (e.g. Fekel Watson 1998 ) and from WISE , although the latter’s wavelength coverage does not reach as far into the IR. A close investigation by Rebull et al. ( 2015 ) found that the majority of lithium-rich giants in the literature with reported IR excesses were artefacts in the WISE catalogue or cases of source confusion. However, they do confirm some as real cases of IR excess, and they do find that the stars with the largest IR excess are lithium-rich K giants. Within our data set, there are only 1862 giants with clean WISE detections; that is, they have the cc_flags confusion flag set to 0000 and the ph_qual photometric quality flag set to A for W 1 and W 4 . Fig. 9 shows an IR colour–magnitude diagram for these stars, divided in the same way as Fig. 7 with RC stars in the upper panels, RGB stars in the lower panels, all stars in the left-hand panels, and the lithium-rich stars highlighted in the right-hand panels. There are 549 RC stars