Connection between planetary He I [lambda] 10 830 Å absorption and extreme-ultraviolet emission of planet-host stars
Context. The detection of the He I λ10 830 Å triplet in exoplanet atmospheres has opened a new window for probing planetary properties, including atmospheric escape. Unlike Lyman α, the triplet is significantly less affected by interstellar medium (ISM) absorption. Sufficient X-ray and extreme ultr...
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| Main Authors: | , , , , , , , , , , , , , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
January 2025
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| In: |
Astronomy and astrophysics
Year: 2025, Volume: 693, Pages: 1-22 |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/202451680 |
| Online Access: | Verlag, kostenfrei, Volltext: https://doi.org/10.1051/0004-6361/202451680 Verlag, kostenfrei, Volltext: https://www.aanda.org/articles/aa/abs/2025/01/aa51680-24/aa51680-24.html 
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| Author Notes: | J. Sanz-Forcada, M. López-Puertas, M. Lampón, S. Czesla, L. Nortmann, J.A. Caballero, M.R. Zapatero Osorio, P.J. Amado, F. Murgas, J. Orell-Miquel, E. Pallé, A. Quirrenbach, A. Reiners, I. Ribas, A. Sánchez-López, and E. Solano |
| Summary: | Context. The detection of the He I λ10 830 Å triplet in exoplanet atmospheres has opened a new window for probing planetary properties, including atmospheric escape. Unlike Lyman α, the triplet is significantly less affected by interstellar medium (ISM) absorption. Sufficient X-ray and extreme ultraviolet (XUV) stellar irradiation may trigger the formation of the He I triplet via photoionization and posterior recombination processes in the planet atmospheres. Only a weak trend between stellar XUV emission and the planetary He I strength has been observed so far. Aims. We aim to confirm this mechanism for producing near-infrared He I absorption in exoplanetary atmospheres by examining a substantial sample of planetary systems. Methods. We obtained homogeneous measurements of the planetary He I line equivalent width and consistently computed the stellar XUV ionizing irradiation. Our first step was to derive new coronal models for the planet-host stars. We used updated data from the X-exoplanets database, archival X-ray spectra of M-type stars (including AU Mic and Proxima Centauri), and new XMM-Newton X-ray data recently obtained for the CARMENES project. These data were complemented at longer wavelengths with publicly available HST, FUSE, and EUVE spectra. A total of 75 stars are carefully analyzed to obtain a new calibration between X-ray and extreme ultraviolet (EUV) emission. Results. Two distinct relationships between stellar X-ray emission (5-100 Å) and EUV H (100-920 Å) or EUV He (100-504 Å) radiation are obtained to scale the emission from late-type (F to M) stellar coronae. A total of 48 systems with reported planetary He I λ 10 830 Å studies, including 21 positive detections and 27 upper limits, exhibit a robust relationship between the strength of the planetary He I feature and the ionizing XUV He received by the planet, corrected by stellar and planetary radii, as well as the planet’s gravitational potential. Some outliers could be explained by a different atmospheric composition or the lack of planetary gaseous atmospheres. This relation may serve as a guide to predict the detectability of the He I λ 10 830 Å absorption in exoplanet atmospheres. |
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| Item Description: | Online veröffentlicht: 24 Januar 2025 Gesehen am 01.08.2025 Im Titel ist "lambda" als griechischer Buchstabe dargestellt |
| Physical Description: | Online Resource |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/202451680 |