Results 61 to 70 of about 164 (131)
The Astronomical JournalYoung exoplanets trace planetary evolution, in particular the atmospheric mass loss that is most dynamic in youth. However, the high activity level of young stars can mask or mimic the spectroscopic signals of atmospheric mass loss.
Daniel M. Krolikowski +5 more
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An interpretation of cycle periods of stellar chromospheric activity
The Astrophysical Journal, 1993 We propose (P cyc /P rot ) 2 , the square of the ratio of the characteristic oscillatory timescales of stellar chromospberic activity to the rotation period, as a useful parameterization of the stellar activity cycle and as the observational equivalent of the theoretical dynamo number, N D . (P cyc /P rot ) 2 can be obtained observationally from 25 yr
W. H. Soon, S. L. Baliunas, Q. Zhang
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The Influence of Chromospheric Activity on Line Formation
The Astrophysical JournalOne of the primary sources of stellar spectral variability is magnetic activity. While our current understanding of chromospheric activity is largely derived from specific lines sensitive to chromospheric heating, such as the Ca ii H and K doublet ...
Mariela C. Vieytes +2 more
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Chromospheric and Coronal Indicators of Stellar Magnetic Structure [PDF]
Symposium - International Astronomical Union, 1983 This paper discusses attempts to derive information on magnetic structure in late-type stars, only from emission fluxes in the cores of the Ca II H and K lines, in UV emission lines and in soft X-rays — and from relations between these emission fluxes. However simpleminded and indirect this approach may seem, it brings out stimulating results.
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Betelgeuse: Detection of the Expanding Wake of the Companion Star
The Astrophysical JournalRecent analyses conclude that Betelgeuse, a red supergiant star (HD 39801), likely has a companion object with a period of ∼2000 days orbiting at only 2.3 R _⋆ , deep in the chromosphere of the supergiant.
Andrea K. Dupree +3 more
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Correlating Intrinsic Stellar Parameters with Mg ii Self-reversal Depths
The Astrophysical JournalThe Mg ii h&k emission lines (2803, 2796 Å) are a useful tool for understanding stellar chromospheres and transition regions due to their intrinsic brightness, relatively low interstellar medium (ISM) absorption interference, and abundance
Anna Taylor +4 more
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Inhomogeneity in the Local ISM and Its Relation to the Heliosphere. [PDF]
Space Sci Rev, 2022 Linsky J +3 more
europepmc +1 more source
The Astrophysical Journal Supplement SeriesAbstract Accurately characterizing the intrinsic stellar photometric noise induced by stellar astrophysics, such as stellar activity, granulation, and oscillations, is of crucial importance for detecting transiting exoplanets. In this study, we investigate the relation between the intrinsic stellar photometric noise, quantified by the ...
Jinghua Zhang +11 more
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Lyα Emission from K and M Dwarfs: Intrinsic Profiles, Variability, and Flux in the Habitable Zone
The Astrophysical JournalLyman-alpha (Ly α ) is the most prominent ultraviolet (UV) emission line in low-mass stars, playing a crucial role in exoplanet atmospheric photochemistry, heating, and escape.
Sarah Peacock +6 more
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HWO Target Stars and Systems: A Survey of Archival UV and X-Ray Data
The Astronomical JournalWe assess archival high-energy data for key stars on the Habitable Worlds Observatory (HWO) Target Stars and Systems 2025 list, as stellar radiation is critical to shaping and interpreting planetary atmospheres.
Sarah Peacock +16 more
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