SPLUSJ210428.01-004934.2: An Ultra Metal-Poor Star Identified from Narrowband Photometry

TL;DR

This paper reports the discovery of an ultra metal-poor star identified through narrowband photometry, confirmed by spectroscopy, with unique chemical properties suggesting it may be a second-generation star, demonstrating the effectiveness of this detection method.

Contribution

The study demonstrates that narrow-band photometry from S-PLUS can effectively identify ultra metal-poor stars, including those with extremely low carbon abundance, expanding the search for primordial stars.

Findings

Confirmed ultra metal-poor star with [Fe/H]=-4.03

Star has the lowest known carbon abundance among UMP stars

Potential identification of a second-generation star

Abstract

We report on the discovery of SPLUS J210428.01-004934.2, an ultra metal-poor (UMP) star first identified from the narrow-band photometry of the Southern Photometric Local Universe Survey (S-PLUS) Data Release 1, in the SDSS Stripe 82 region. Follow-up medium- and high-resolution spectroscopy (with Gemini South and Magellan-Clay, respectively) confirmed the effectiveness of the search for low-metallicity stars using the S-PLUS narrow-band photometry. At [Fe/H]=-4.03, SPLUS J2104-0049 has the lowest detected carbon abundance, A(C)=+4.34, when compared to the 34 previously known UMP stars in the literature, which is an important constraint on its stellar progenitor and also on stellar evolution models at the lowest metallicities. Based on its chemical abundance pattern, we speculate that SPLUS J2104-0049 could be a bonafide second-generation star, formed from a gas cloud polluted by a single metal-free ~30Mo star. This discovery opens the possibility of finding additional UMP stars directly from narrow-band photometric surveys, a potentially powerful method to help complete the inventory of such peculiar objects in our Galaxy.