The Fe I 4377 Line as a Solar Faculae Indicator: Insights from Spectral Ratio Analysis

arXiv:2607.29455 · astro-ph.SR, astro-ph.EP, astro-ph.IM · Submitted 2026-07-31 · Read on arXiv

Katlyn L. Hobbs, Christopher A. Watson, Jean C. Costes, Yvonne Unruh, Dana Clarice Yaptangco, Krishnamurthy Sowmya, Mitchell E. Young, Ernst J. W. de Mooij, Alexander G. M. Pietrow, Pál Váradi Nagy, Alexander I. Shapiro, Veronika Witzke, Federica Rescigno, Ryan A. Rubenzahl, Megan Bedell, Andrew Collier Cameron, Xavier Dumusque, Sean M. O'Brien, Benjamin M. J. Cadell, Baptiste Klein, Niamh Mallaghan, Niamh K. O'Sullivan, Toby Rodel, Sara Tavella

Queen's University Belfast · Queen's University Belfast · Queen's University Belfast · Imperial College London · Imperial College London · University of Graz · Queen's University Belfast · Queen's University Belfast · Leibniz-Institut für Astrophysik Potsdam · Independent Researcher · Max-Planck-Institut für Sonnensystemforschung · University of Graz · University of Birmingham · Flatiron Institute · Flatiron Institute · University of St Andrews · University of Geneva · Queen's University Belfast · Queen's University Belfast · University of Oxford · Queen's University Belfast · University of Oxford · Queen's University Belfast · University of Geneva

astro-ph.SR, astro-ph.EP, astro-ph.IM

Submitted: 2026-07-31

Comments: 16 pages, 12 figures. Accepted for publication in MNRAS

DOI: 10.1093/mnras/stag1462

Code: https://github.com/melix/astro4j

License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/

Terminology

• Active Regions — 16× in this paper · explained in 1 episode
• Core — 6× in this paper · explained in 2 episodes
• Solar Dynamics Observatory — 5× in this paper
• Trace — 5× in this paper · explained in 2 episodes
• Spectral Ratio Analysis — 4× in this paper
• Society of Photo-Optical Instrumentation Engineers — 3× in this paper
• Accuracy — 2× in this paper · explained in 1 episode
• Spectral Signature — 2× in this paper · explained in 2 episodes
• Transmission spectroscopy — 2× in this paper · explained in 2 episodes
• UK Science and Technology Facilities Council — 2× in this paper
• Aperture — 1× in this paper · explained in 1 episode
• Benchmark — 1× in this paper · explained in 2 episodes
• Consistency — 1× in this paper · explained in 3 episodes
• Data Reduction Software — 1× in this paper
• Degeneracy — 1× in this paper · explained in 3 episodes
• European Research Council — 1× in this paper
• Helioseismic and Magnetic Imager — 1× in this paper
• Local Thermodynamic Equilibrium — 1× in this paper
• Metallicity — 1× in this paper · explained in 3 episodes
• Robustness — 1× in this paper · explained in 5 episodes
• Scottish Universities Physics Alliance — 1× in this paper
• Signal-to-noise ratio (SNR) — 1× in this paper · explained in 2 episodes

Sources

• Disentangling stellar activity and planetary signals
• Precise Radial Velocities
• Extreme Precision Radial Velocity Working Group Final Report
• Data-Driven Modeling of Telluric Features and Stellar Variability with StellarSpectraObservationFitting.jl
• EXPRES: A Next Generation RV Spectrograph in the Search for Earth-like Worlds
• HARPS3 for a Roboticized Isaac Newton Telescope

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