Results 71 to 80 of about 1,834 (171)
The Astrophysical Journal Supplement SeriesBased on the Ca ii H and K lines observed by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, we employ the photospheric ( ${R}_{{\rm{HK}}}^{{\prime} }$ ) and basal ( ${R}_{{\rm{HK}},L}^{+}$ ) flux-calibrated chromospheric activity indices ...
Weitao Zhang, Han He, Jun Zhang
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, 2017 Although observational data unequivocally point out to the presence of chromospheres in red giant stars, no attempts have been made so far to model them using 3D hydrodynamical model atmospheres.
Klevas, Jonas +3 more
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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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Studies of the local interstellar medium [PDF]
The existing ultraviolet and optical data concerning late-type stars are discussed along with the acquisition and reduction of additional ultraviolet and simultaneous ground-based observation.
Dupree, A. K.
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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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PHOENIX model chromospheres of mid- to late-type M dwarfs
, 2005 We present semi-empirical model chromospheres computed with the atmosphere code PHOENIX. The models are designed to fit the observed spectra of five mid- to late-type M dwarfs. Next to hydrogen lines from the Balmer series we used various metal lines, e.
Andretta +36 more
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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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An IUE's eye view of cool-star outer atmospheres [PDF]
Three topics are discussed which together demonstrate the power of the IUE to probe the occurrences of chromospheres and coronas in the cool half of the HR diagram.
Ayres, T. R.
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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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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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