Convective characteristics of Fe I lines across the solar disc

Abstract

Solar convection is visible as a net blueshift of absorption lines, which becomes apparent when observing quiet Sun granulation. This blueshift exhibits variations from the disc centre to the solar limb due to differing projection angles onto the solar atmosphere. Our goal is to investigate convective Doppler velocities based on observations from the disc centre to the solar limb. Consequently, we aim to improve our understanding of atmospheric hydrodynamics and contribute to the improvement of solar and stellar atmospheric models. We used resolved quiet-Sun spectra to investigate the convective velocity shifts of more than 1000\,\ion{Fe}{I} lines across multiple centre-to-limb positions on the solar disc. We determined the Doppler velocities with respect to the line depth. Additionally, we calculated the formation temperature and investigated its correlation with Doppler velocities. The general behaviour of convective line shifts shows a decreasing blueshift as the lines become deeper for all observing positions from the centre to limb. For spectra obtained at the solar limb, even deeper lines exhibit redshifts. We observe a velocity trend for the different observation angles, with a less pronounced convective blueshift towards the solar limb. Convective velocities show a wavelength dependence for each observing angle when analysing on the basis of line depths. We observe a decreasing convective blueshift as the formation temperatures of the lines decrease. The velocity change over temperature ranges proceeds slower towards the solar limb. When investigating Doppler velocities with respect to formation temperature, the disc centre does not exhibit the strongest blueshift.

References in corpus (14)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• Convective blueshifts in the solar atmosphere: III. High-accuracy observations of spectral lines in the visible
• PySME -- Spectroscopy Made Easier
• Measuring precise radial velocities on individual spectral lines. III. Dependence of stellar activity signal on line formation temperature
• Convective blueshift strengths of 810 F to M solar-type stars
• The solar gravitational redshift from HARPS-LFC Moon spectra. A test of the General Theory of Relativity
• Planet and star synergy at high spectral resolution. A rationale for the characterisation of exoplanet atmospheres. I. The Infrared
• Spatially resolved spectroscopy across stellar surfaces. I. Using exoplanet transits to analyze 3-D stellar atmospheres
• FTS atlas of the Sun's spectrally resolved center-to-limb variation
• The IAG spectral atlas of the spatially resolved Sun: Centre-to-limb observations
• Center-to-limb variation of spectral lines and continua observed with SST/CRISP and SST/CHROMIS
• Solar Center--Limb Variation of the Strengths of Spectral Lines: Classification and Interpretation of Observed Trends
• Center--limb variation of solar photospheric microturbulence
• Newly formed downflow lanes in exploding granules in the solar photosphere

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• Towards understanding stellar variability at the sub m/s level: granulation-induced variability across the optical spectrum