Center-to-limb variation of spectral lines and continua observed with SST/CRISP and SST/CHROMIS

TL;DR

This study provides a comprehensive set of standardized spectral line profiles across the solar disk, aiding the validation of atmospheric models and enhancing understanding of stellar and exoplanet atmospheres.

Contribution

The paper introduces a new method for creating standardized, high-resolution spectral line profiles from SST observations, covering the entire solar disk from center to limb.

Findings

50 averaged spectral profiles across the solar disk

Profiles include key spectral lines and continua

Data available as machine-readable tables

Abstract

Observations of center-to-limb variations (CLV) of spectral lines and continua provide a good test for the accuracy of models of solar and stellar atmospheric structure and spectral-line formation. They are also widely used to constrain elemental abundances and are becoming increasingly important in atmospheric studies of exoplanets. However, only a few such data sets exist for chromospheric lines. We aim to create a set of standard profiles by means of mosaics made with the CRISP and CHROMIS instruments of the Swedish 1-m Solar Telescope (SST), as well as to explore the robustness of said profiles obtained using this method. For each spectral line we use a mosaic that ranges from the center to the limb. Each of these mosaics are averaged down to 50 individual spectral profiles, spaced by 0.02 in the $\mu$ scale. These profiles are corrected for p-mode oscillations, and their line parameters (equivalent width, line shift, full-width at half-maximum, and line depth) are then compared against literature values where possible. We present a set of 50 average profiles that are spaced equidistantly along the cosine of the heliocentric angle ($\mu$) by steps of 0.02 for five continuum points between 4001 and 7772 \AA, as well as ten of the most commonly observed spectral lines at the SST (Ca II H & K, H$\beta$, Mg I 5173 \AA, C I 5380 \AA, Fe I 6173 \AA, Fe I 6301 \AA, H$\alpha$, O I 7772 \AA, and Ca II 8542 \AA). Center-to-limb variation of line profiles and continua are shared in the CDS as machine-readable tables; providing a quantitative constraint on theoretical models that aim to model stellar atmospheres.