From Starspots to Stellar Coronal Mass Ejections -- Revisiting Empirical Stellar Relations

Abstract

Upcoming missions, including the James Webb Space Telescope, will soon characterize the atmospheres of terrestrial-type exoplanets in habitable zones around cool K- and M-type stars searching for atmospheric biosignatures. Recent observations suggest that the ionizing radiation and particle environment from active cool planet hosts may be detrimental for exoplanetary habitability. Since no direct information on the radiation field is available, empirical relations between signatures of stellar activity, including the sizes and magnetic fields of starspots, are often used. Here, we revisit the empirical relation between the starspot size and the effective stellar temperature and evaluate its impact on estimates of stellar flare energies, coronal mass ejections, and fluxes of the associated stellar energetic particle events.

arXiv comment14 pages, 4 figures, 2 tables, accepted for publication in The Astrophysical Journal (07/11/2020)

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• Untangling the Galaxy. IV. Empirical Constraints on Angular Momentum Evolution and Gyrochronology for Young Stars in the Field
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• Magnetic Activity-Rotation-Age-Mass Relations in Late Pre-main Sequence Stars
• A Machine Learning approach for correcting radial velocities using physical observables
• Characterization of starspots on a young M-dwarf K2-25: multi-band observations of stellar photometric variability and planetary transits
• Revisiting Empirical Solar Energetic Particle Scaling Relations I. Solar flares
• The energetic particle environment of a GJ 436 b-like planet
• Hiding in plain sight: observing planet-starspot crossings with the James Webb Space Telescope
• Stellar Energetic Particle Transport in the Turbulent and CME-disrupted Stellar Wind of AU~Microscopii
• Blackbody temperature of 200+ stellar flares observed with the CoRoT satellite
• Measuring the Temperature of Starspots from Multi-Filter Photometry
• Do Young Suns Produce Frequent, Massive CMEs? Results from Five-year Dedicated Optical Observations of EK Draconis and V889 Hercules
• Multi-band, Multi-epoch Photometry of the Spot-crossing System TOI-3884: Refined System Geometry and Spot Properties
• Solar and stellar flares: frequency, active regions and stellar dynamo
• GEMS JWST: Transmission spectroscopy of TOI-5205b reveals significant stellar contamination and a metal-poor atmosphere
• Chromaticity of stellar activity in radial velocities : Anti-correlated families of lines on the M dwarf EV Lac with SPIRou and SOPHIE
• Clarifying Physical Properties of Magnetic Fields in Sunspots
• Analysis of KIC 7023917 -- spotted low-mass ratio eclipsing binary with $\delta$ Scuti pulsations
• Starspots on eclipsing giant stars I.: The sample and eclipse mapping examples
• Homogeneous search for spot transits in Kepler and TESS photometry of K $-$ M-type main-sequence stars
• Stellar spots cause measurable variations in atmospheric metallicity
• Comparing the Sun to Sun-like stars. On the importance of addressing faculae/spot domination
• Kepler-411 star activity: connection between starspots and superflares