# The Pristine survey II: a sample of bright stars observed with FEROS

## TL;DR

This paper presents spectroscopic follow-up of bright stars from the Pristine Survey using FEROS, highlighting the effectiveness of combining Pristine photometry with APASS data for metallicity estimation in bright stars.

## Contribution

It demonstrates that Pristine photometry, when combined with APASS data, provides reliable metallicity estimates for bright stars, addressing saturation issues in SDSS data.

## Key findings

- Bright stars (g<=15) are too saturated in SDSS gri bands for accurate metallicity.
- Pristine photometry combined with APASS gri photometry yields reliable metallicity estimates.
- Spectroscopic follow-up confirms the effectiveness of the combined photometric approach.

## Abstract

Extremely metal-poor (EMP) stars are old objects formed in the first Gyr of the Universe. They are rare and, to select them, the most successful strategy has been to build on large and low-resolution spectroscopic surveys. The combination of narrow- and broad band photometry provides a powerful and cheaper alternative to select metal-poor stars. The on-going Pristine Survey is adopting this strategy, conducting photometry with the CFHT MegaCam wide field imager and a narrow-band filter centred at 395.2 nm on the CaII-H and -K lines. In this paper we present the results of the spectroscopic follow-up conducted on a sample of 26 stars at the bright end of the magnitude range of the Survey (g<=15), using FEROS at the MPG/ESO 2.2 m telescope. From our chemical investigation on the sample, we conclude that this magnitude range is too bright to use the SDSS gri bands, which are typically saturated. Instead the Pristine photometry can be usefully combined with the APASS gri photometry to provide reliable metallicity estimates.