Speaker
Description
Phosphorus is an odd-Z element of astrobiological and nucleosynthetic interest, yet its Galactic origin remains poorly constrained because observable stellar P lines are weak and mostly located outside the optical wavelength range. I will present phosphorus abundance measurements for 102 evolved stars, including 82 giants in 24 open clusters and 20 classical Cepheids, based on high-resolution near-infrared spectra obtained with GIANO-B.
By combining P abundances with independently constrained stellar and cluster ages, this sample provides an age-resolved view of phosphorus enrichment on the young side of the Milky Way disk. We confirm the previously observed modest decline of [P/Fe] with increasing [Fe/H] around solar metallicity. More importantly, the open-cluster sample reveals a structured P–age relation, with two apparent regimes. For clusters older than about 1 Gyr, phosphorus abundance increases with stellar age, suggesting that these systems preserve a fossil record of diverse enrichment histories and more intense star formation in earlier Galactic environments. In contrast, clusters younger than about 1 Gyr and Cepheids show a nearly flat trend with age, consistent with a more quiescent recent chemical history in the local disk.
This age-resolved abundance pattern provides an empirical benchmark for Galactic chemical-evolution models of phosphorus. While massive stars remain the dominant expected source of P, the behaviour of the youngest populations may point to an additional delayed or metallicity-dependent contribution, potentially from lower- or intermediate-mass stellar sources. I will also discuss how robust spectral-synthesis and line-selection methods, including recent developments in PySME for survey-scale abundance analysis, can help extend such nucleosynthetic constraints to larger stellar samples.
| Category | Observation |
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