A Semiempirical Estimate of Solar Extreme-ultraviolet Evolution from 10 Myr to 10 Gyr
The extreme-ultraviolet (EUV; 100–911 Å) spectra of F, G, K, and M stars provide diagnostics of the stellar chromosphere through the corona, with line and continuum formation temperatures spanning roughly 10 ^4 –10 ^7 K. The EUV stellar spectrum in turn drives atmospheric photochemistry and numerous...
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2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-3881/adefdf |
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| author | Kevin France Girish Duvvuri Cynthia S. Froning Alexander Brown P. Christian Schneider J. Sebastian Pineda David Wilson Allison Youngblood Vladimir S. Airapetian Kosuke Namekata Yuta Notsu Tristen Sextro |
| author_facet | Kevin France Girish Duvvuri Cynthia S. Froning Alexander Brown P. Christian Schneider J. Sebastian Pineda David Wilson Allison Youngblood Vladimir S. Airapetian Kosuke Namekata Yuta Notsu Tristen Sextro |
| author_sort | Kevin France |
| collection | DOAJ |
| description | The extreme-ultraviolet (EUV; 100–911 Å) spectra of F, G, K, and M stars provide diagnostics of the stellar chromosphere through the corona, with line and continuum formation temperatures spanning roughly 10 ^4 –10 ^7 K. The EUV stellar spectrum in turn drives atmospheric photochemistry and numerous escape processes on orbiting planets, and is often combined with the stellar X-ray flux to make up the X-ray and ultraviolet (XUV) irradiance. However, very few direct EUV spectra of other stars exist in the archive, and as a result, X-ray scaling relations are often assumed for the XUV evolution of cool stars. In this work, we present a new study of the EUV history of solar-type stars, using scaling relations based on transition region/coronal far-ultraviolet emission lines and differential emission measure-based synthetic spectra to provide a semiempirical estimate of the EUV evolution of the Sun over the ≈10 Myr–10 Gyr age range for the first time. We utilize new and archival Hubble Space Telescope observations of solar analogs ( T _⊙ ± 150 K for stars older than 100 Myr) and “Young Suns” (age < 100 Myr) that will evolve into main-sequence early G-type stars to predict the 90–360 Å EUV flux from a sample of 23 stars. We find that the EUV activity evolution for solar-type stars follows a two-component behavior: a saturated L (EUV)/ L _bol plateau (at a level of about 10 ^−4 ) followed by a power-law decay ( α ≈ −1.1) after ages of ≈50–100 Myr. Consequently, the EUV flux incident at 1 au around solar analogs varies over the lifetime of the Sun, ranging from 100× the present-day UV irradiance at 10 Myr to 0.3× the present-day level at 10 Gyr. We find that the EUV luminosity is approximately the same as the soft X-ray luminosity up to approximately 1 Gyr, after which the EUV luminosity of the stars dominates. In comparison to Sun-like stars, the EUV saturation level of early/mid M dwarfs is several times higher and lasts ∼10–20 times longer. |
| format | Article |
| id | doaj-art-d8fa446118bf474ba873d04fe6ebf115 |
| institution | DOAJ |
| issn | 1538-3881 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| spelling | doaj-art-d8fa446118bf474ba873d04fe6ebf1152025-08-20T03:03:15ZengIOP PublishingThe Astronomical Journal1538-38812025-01-01170315910.3847/1538-3881/adefdfA Semiempirical Estimate of Solar Extreme-ultraviolet Evolution from 10 Myr to 10 GyrKevin France0https://orcid.org/0000-0002-1002-3674Girish Duvvuri1https://orcid.org/0000-0002-7119-2543Cynthia S. Froning2https://orcid.org/0000-0001-8499-2892Alexander Brown3https://orcid.org/0000-0003-2631-3905P. Christian Schneider4https://orcid.org/0000-0002-5094-2245J. Sebastian Pineda5https://orcid.org/0000-0002-4489-0135David Wilson6https://orcid.org/0000-0001-9667-9449Allison Youngblood7https://orcid.org/0000-0002-1176-3391Vladimir S. Airapetian8https://orcid.org/0000-0003-4452-0588Kosuke Namekata9https://orcid.org/0000-0002-1297-9485Yuta Notsu10https://orcid.org/0000-0002-0412-0849Tristen Sextro11https://orcid.org/0009-0006-0318-3385Laboratory for Atmospheric and Space Physics, University of Colorado Boulder , Boulder, CO 80309, USA ; kevin.france@colorado.edu; Department of Astrophysical and Planetary Sciences, University of Colorado Boulder , Boulder, CO 80309, USA; Center for Astrophysics and Space Astronomy, University of Colorado Boulder , Boulder, CO 80309, USADepartment of Physics and Astronomy, Vanderbilt University , Nashville, TN 37235, USASouthwest Research Institute , San Antonio, TX 78238, USACenter for Astrophysics and Space Astronomy, University of Colorado Boulder , Boulder, CO 80309, USAChristian-Albrechts University , Leibnizstraße 15, 24118 Kiel, GermanyLaboratory for Atmospheric and Space Physics, University of Colorado Boulder , Boulder, CO 80309, USA ; kevin.france@colorado.eduLaboratory for Atmospheric and Space Physics, University of Colorado Boulder , Boulder, CO 80309, USA ; kevin.france@colorado.eduExoplanets and Stellar Astrophysics Laboratory, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USANASA GSFC/SEEC , Greenbelt, MD, USA; Department of Physics, American University , Washington, DC, USAHeliophysics Science Division, NASA Goddard Space Flight Center , 8800 Greenbelt Road, Greenbelt, MD 20771, USA; The Catholic University of America , 620 Michigan Avenue, N.E., Washington, DC 20064, USA; The Hakubi Center for Advanced Research, Kyoto University , Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501, Japan; Department of Physics, Kyoto University , Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, JapanLaboratory for Atmospheric and Space Physics, University of Colorado Boulder , Boulder, CO 80309, USA ; kevin.france@colorado.edu; Department of Astrophysical and Planetary Sciences, University of Colorado Boulder , Boulder, CO 80309, USA; National Solar Observatory , Boulder, CO 80309, USADepartment of Astronomy and Astrophysics, Pennsylvania State University , University Park, PA 16802, USAThe extreme-ultraviolet (EUV; 100–911 Å) spectra of F, G, K, and M stars provide diagnostics of the stellar chromosphere through the corona, with line and continuum formation temperatures spanning roughly 10 ^4 –10 ^7 K. The EUV stellar spectrum in turn drives atmospheric photochemistry and numerous escape processes on orbiting planets, and is often combined with the stellar X-ray flux to make up the X-ray and ultraviolet (XUV) irradiance. However, very few direct EUV spectra of other stars exist in the archive, and as a result, X-ray scaling relations are often assumed for the XUV evolution of cool stars. In this work, we present a new study of the EUV history of solar-type stars, using scaling relations based on transition region/coronal far-ultraviolet emission lines and differential emission measure-based synthetic spectra to provide a semiempirical estimate of the EUV evolution of the Sun over the ≈10 Myr–10 Gyr age range for the first time. We utilize new and archival Hubble Space Telescope observations of solar analogs ( T _⊙ ± 150 K for stars older than 100 Myr) and “Young Suns” (age < 100 Myr) that will evolve into main-sequence early G-type stars to predict the 90–360 Å EUV flux from a sample of 23 stars. We find that the EUV activity evolution for solar-type stars follows a two-component behavior: a saturated L (EUV)/ L _bol plateau (at a level of about 10 ^−4 ) followed by a power-law decay ( α ≈ −1.1) after ages of ≈50–100 Myr. Consequently, the EUV flux incident at 1 au around solar analogs varies over the lifetime of the Sun, ranging from 100× the present-day UV irradiance at 10 Myr to 0.3× the present-day level at 10 Gyr. We find that the EUV luminosity is approximately the same as the soft X-ray luminosity up to approximately 1 Gyr, after which the EUV luminosity of the stars dominates. In comparison to Sun-like stars, the EUV saturation level of early/mid M dwarfs is several times higher and lasts ∼10–20 times longer.https://doi.org/10.3847/1538-3881/adefdfSolar extreme ultraviolet emissionStellar activityExoplanet atmospheres |
| spellingShingle | Kevin France Girish Duvvuri Cynthia S. Froning Alexander Brown P. Christian Schneider J. Sebastian Pineda David Wilson Allison Youngblood Vladimir S. Airapetian Kosuke Namekata Yuta Notsu Tristen Sextro A Semiempirical Estimate of Solar Extreme-ultraviolet Evolution from 10 Myr to 10 Gyr The Astronomical Journal Solar extreme ultraviolet emission Stellar activity Exoplanet atmospheres |
| title | A Semiempirical Estimate of Solar Extreme-ultraviolet Evolution from 10 Myr to 10 Gyr |
| title_full | A Semiempirical Estimate of Solar Extreme-ultraviolet Evolution from 10 Myr to 10 Gyr |
| title_fullStr | A Semiempirical Estimate of Solar Extreme-ultraviolet Evolution from 10 Myr to 10 Gyr |
| title_full_unstemmed | A Semiempirical Estimate of Solar Extreme-ultraviolet Evolution from 10 Myr to 10 Gyr |
| title_short | A Semiempirical Estimate of Solar Extreme-ultraviolet Evolution from 10 Myr to 10 Gyr |
| title_sort | semiempirical estimate of solar extreme ultraviolet evolution from 10 myr to 10 gyr |
| topic | Solar extreme ultraviolet emission Stellar activity Exoplanet atmospheres |
| url | https://doi.org/10.3847/1538-3881/adefdf |
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