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# Stellar Loci VI: An Updated Catalog of the Best and Brightest Metal-poor Stars

Shuai Xu, Haibo Yuan, Ruoyi Zhang, Haining Li, Timothy C. Beers, Yang Huang
arXiv:2207.02371

Submitted on 5 July 2022

## Abstract

We employ Gaia, 2MASS, and ALLWISE photometry, as well as astrometric data from Gaia, to search for relatively bright very metal-poor ([Fe/H] $<-2.0$; VMP) giant star candidates using three different criteria: 1) our derived Gaia photometric metallicities, 2) the lack of stellar molecular absorption near 4.6 microns, and 3) their high tangential velocities. With different combinations of these criteria, we have identified six samples of candidates with $G<$ 15: the Gold sample (24,304 candidates), the Silver GW sample (40,157 candidates), the Silver GK sample (120,452 candidates), the Bronze G sample (291,690 candidates), the Bronze WK sample (68,526 candidates), and the Low $b$ sample (4,645 candidates). The Low $b$ sample applies to sources with low Galactic lattitude, $|b|<{10}^{\circ }$, while the others are for sources with $|b|>{10}^{\circ }$. By cross-matching with results derived from medium-resolution ($R\sim$ 1800) from LAMOST DR8, we establish that the success rate for identifying VMP stars is 60.1$\mathrm{%}$ for the Gold sample, 39.2$\mathrm{%}$ for the Silver GW sample, 41.3$\mathrm{%}$ for the Silver GK sample, 15.4$\mathrm{%}$ for the Bronze G sample, 31.7$\mathrm{%}$ for the Bronze WK sample, and 16.6$\mathrm{%}$ for the Low $b$ sample, respectively. An additional strict cut on the quality parameter $RUWE<1.1$ can further increase the success rate of the Silver GW, Silver GK, and Bronze G samples to 46.9$\mathrm{%}$, 51.6$\mathrm{%}$, and 29.3$\mathrm{%}$, respectively. Our samples provide valuable targets for high-resolution follow-up spectroscopic observations, and are made publicly available.

## Preprint

Comment: 14pages, 8 figures, 4 tables, data is available in http://paperdata.china-vo.org/Xu.Shuai/2022/VMP/VMP_candidate.zip

Subjects: Astrophysics - Solar and Stellar Astrophysics; Astrophysics - Astrophysics of Galaxies