On the center-to-limb variations of the He I 10 830 Å triplet
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arXiv
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2025
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| author | Pietrow, A. G. M. Kuckein, C. Verma, M. Denker, C. Arjona, J. C. Trelles Kamlah, R. Poppenhäger, K. |
| author_facet | Pietrow, A. G. M. Kuckein, C. Verma, M. Denker, C. Arjona, J. C. Trelles Kamlah, R. Poppenhäger, K. |
| contents | We present high-resolution spectroscopic observations of the quiet-Sun center-to-limb variations (CLV) of the He I triplet at 10 830 Å and the nearby Si I 10 827 Å line, observed with GREGOR Infrared Spectrograph (GRIS) and the improved High-resolution Fast Imager (HiFI+). The observations cover the interval $μ= [0.1,\, 1.0]$, where $μ$ is the cosine of the heliocentric angle. At each $μ$-position, the spectra are spatially averaged over 0.02 $μ$, and the resulting CLVs are given both as these averaged data points and as smooth polynomial curves fitted across each wavelength point. The He I spectra were inverted using the HAnle and ZEeman Light (HAZEL) code, showing an increase in optical depth towards the limb and a reversed convective blueshift for the red component, while the blue component was entirely absent. In addition, we find a strong increase in the steepness of the He I CLV compared to that of the nearby continuum. The Si I showed a behavior more typical of photospheric lines, namely shallower CLV, a reduction in width and depth, and a more typical convective blueshift. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2511_14331 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | On the center-to-limb variations of the He I 10 830 Å triplet Pietrow, A. G. M. Kuckein, C. Verma, M. Denker, C. Arjona, J. C. Trelles Kamlah, R. Poppenhäger, K. Solar and Stellar Astrophysics Earth and Planetary Astrophysics We present high-resolution spectroscopic observations of the quiet-Sun center-to-limb variations (CLV) of the He I triplet at 10 830 Å and the nearby Si I 10 827 Å line, observed with GREGOR Infrared Spectrograph (GRIS) and the improved High-resolution Fast Imager (HiFI+). The observations cover the interval $μ= [0.1,\, 1.0]$, where $μ$ is the cosine of the heliocentric angle. At each $μ$-position, the spectra are spatially averaged over 0.02 $μ$, and the resulting CLVs are given both as these averaged data points and as smooth polynomial curves fitted across each wavelength point. The He I spectra were inverted using the HAnle and ZEeman Light (HAZEL) code, showing an increase in optical depth towards the limb and a reversed convective blueshift for the red component, while the blue component was entirely absent. In addition, we find a strong increase in the steepness of the He I CLV compared to that of the nearby continuum. The Si I showed a behavior more typical of photospheric lines, namely shallower CLV, a reduction in width and depth, and a more typical convective blueshift. |
| title | On the center-to-limb variations of the He I 10 830 Å triplet |
| topic | Solar and Stellar Astrophysics Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2511.14331 |