Investigating the Temperature Sensitivity of UV Line Ratios in the 280 nm Region of Solar-like Stars

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Main Authors: Penza, Valentina, Criscuoli, Serena, Reda, Raffaele, Bertello, Luca, Bono, Giuseppe, Del Moro, Dario, D'Orazi, Valentina, Giovannelli, Luca, Nigro, Giuseppina, Berrilli, Francesco
Format: Preprint
Published: 2025
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author Penza, Valentina
Criscuoli, Serena
Reda, Raffaele
Bertello, Luca
Bono, Giuseppe
Del Moro, Dario
D'Orazi, Valentina
Giovannelli, Luca
Nigro, Giuseppina
Berrilli, Francesco
author_facet Penza, Valentina
Criscuoli, Serena
Reda, Raffaele
Bertello, Luca
Bono, Giuseppe
Del Moro, Dario
D'Orazi, Valentina
Giovannelli, Luca
Nigro, Giuseppina
Berrilli, Francesco
contents Stellar UV spectra are fundamental diagnostics of physical and magnetic properties of stars. For instance, lines like Mg II at 280 nm serve as valuable indicators of stellar activity, providing insights into the activity levels of Sun-like stars and their potential influence on the atmospheres of orbiting planets. On the other hand, the effective temperature (Teff) is a fundamental stellar parameter, critical for determining stellar properties such as mass, age, composition and evolutionary status. In this study, we investigate the temperature sensitivity of three lines in the mid-ultraviolet range (i.e., Mg II 280.00 nm, Mg I 285.20 nm, and Si I 286.15 nm). Using spectra from the International Ultraviolet Explorer (IUE), we analyze the behavior of the ratios of their corresponding indices (core/continuum) for a sample of calibrating solar-like stars, and find that the ration R = Mg II/Mg I best traces Teff through a log-log relation. The Teff estimated using this relation on a test-sample of solar-like stars agree with the Teff from the literature at the 95% confidence level. The observed results are interpreted making use of Response Functions as diagnostics. This study extends the well-established use of line depth ratio-temperature relationships, traditionally applied in the visible and near-infrared ranges, to the mid-UV spectrum. With the growing interest in stellar UV spectroscopy, results presented in this paper are potentially relevant for future missions as HWO, MANTIS and UVEX.
format Preprint
id arxiv_https___arxiv_org_abs_2503_11878
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Investigating the Temperature Sensitivity of UV Line Ratios in the 280 nm Region of Solar-like Stars
Penza, Valentina
Criscuoli, Serena
Reda, Raffaele
Bertello, Luca
Bono, Giuseppe
Del Moro, Dario
D'Orazi, Valentina
Giovannelli, Luca
Nigro, Giuseppina
Berrilli, Francesco
Solar and Stellar Astrophysics
Stellar UV spectra are fundamental diagnostics of physical and magnetic properties of stars. For instance, lines like Mg II at 280 nm serve as valuable indicators of stellar activity, providing insights into the activity levels of Sun-like stars and their potential influence on the atmospheres of orbiting planets. On the other hand, the effective temperature (Teff) is a fundamental stellar parameter, critical for determining stellar properties such as mass, age, composition and evolutionary status. In this study, we investigate the temperature sensitivity of three lines in the mid-ultraviolet range (i.e., Mg II 280.00 nm, Mg I 285.20 nm, and Si I 286.15 nm). Using spectra from the International Ultraviolet Explorer (IUE), we analyze the behavior of the ratios of their corresponding indices (core/continuum) for a sample of calibrating solar-like stars, and find that the ration R = Mg II/Mg I best traces Teff through a log-log relation. The Teff estimated using this relation on a test-sample of solar-like stars agree with the Teff from the literature at the 95% confidence level. The observed results are interpreted making use of Response Functions as diagnostics. This study extends the well-established use of line depth ratio-temperature relationships, traditionally applied in the visible and near-infrared ranges, to the mid-UV spectrum. With the growing interest in stellar UV spectroscopy, results presented in this paper are potentially relevant for future missions as HWO, MANTIS and UVEX.
title Investigating the Temperature Sensitivity of UV Line Ratios in the 280 nm Region of Solar-like Stars
topic Solar and Stellar Astrophysics
url https://arxiv.org/abs/2503.11878