Among the low-metallicity, low-mass, long-lived stars still visible today, it has become clear that the fraction of carbon-enhanced metal-poor (CEMP) stars increases with decreasing metallicity. Formed from gas clouds enriched with the remnants of previous stellar generations or chemically altered by accreted material from a companion, CEMP stars provide a unique window into the chemical landscape of the early Universe. Understanding the First Stars and the most metal-poor stars inevitably requires an understanding of CEMP stars.
We present F abundances and upper limits in 7 CEMP stars observed with the Immersion Grating INfrared Spectrometer (IGRINS), at the Gemini-south telescope. These new observations delivered high-resolution, high SNR, infrared spectra allowing us to probe significantly deeper into the metal-poor regime. This work presents the results of our observations, including two 2-sigma detections and five upper limits in a variety of CEMP stars. Arguably the most important result is for CS 29498-0043, a CEMP-no star at [Fe/H] = -3.87 with a F detection of [F/Fe] = 2.00, the lowest metallicity star (more than a factor of 10 lower in metallicity than the closest detection) with observed F abundance to date. This measurement enabled us to discriminate between two proposed zero metallicity Population III progenitors; our value is in better agreement with the mixing-and-fallback model which includes enhanced mixing, excluding the non-rotating model without enhanced mixing. This detection represents a pilot, and pioneering, study demonstrating the power of fluorine to explore the nature and properties of supernovae explosions in Population III stars. We discuss the implications and constraints provided by this result. The rest of the sample is presented along with literature data and other nucleosynthesis model predictions when available.
Horarios: November 21, 2023 11:30
Publicado por: Claudia Aguilera