Deliporanidou, E., & Del Zanna, G. (2024). Modelling Stellar Irradiances I: the transition regions of FGKM stars. Monthly Notices of the Royal Astronomical Society, 000, 1–10.
This study aims to improve the modeling of UV spectral lines from stellar transition regions, particularly for anomalous ions, using advanced ionization equilibrium models and to investigate the presence of the First Ionization Potential (FIP) effect in a sample of FGKM stars.
The researchers employed advanced ionization equilibrium models, incorporating density and charge transfer effects, to model UV stellar irradiances for four stars: ε Eridani (K2 V), α Centauri A (G2 V), Procyon (F5 V), and Proxima Centauri (M5.5 Ve). They analyzed STIS UV spectral data, measured line fluxes, and used O IV and O V lines as density diagnostics. A simple Differential Emission Measure (DEM) modeling approach was adopted to derive relative chemical abundances in the transition regions of the stars.
The study highlights the importance of incorporating density and charge transfer effects in ionization equilibrium models for accurate modeling of stellar transition regions. The findings suggest that the FIP effect, while observed in stellar coronae, might not be as prominent in transition regions, implying a different physical mechanism governing elemental abundances in these cooler atmospheric layers.
This research significantly contributes to our understanding of stellar atmospheres and the physical processes shaping their chemical compositions. The improved ionization equilibrium models provide valuable tools for analyzing UV spectra and deriving accurate stellar abundances, which are crucial for studying stellar evolution, exoplanetary atmospheres, and the interstellar medium.
The study focuses on a limited sample of four stars. Expanding the analysis to a larger and more diverse stellar sample would strengthen the conclusions regarding the FIP effect in transition regions. Further research could explore the potential influence of stellar activity cycles and magnetic fields on the observed abundances.
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by Evangelia De... at arxiv.org 10-04-2024
https://arxiv.org/pdf/2410.02607.pdfDeeper Inquiries