Utilizing the PHOENIX synthetic spectra, we investigated the impact of spectral resolution on the calculation of S-indices. We found that for spectra with a resolution lower than ≈30,000, it is crucial to calibrate S-indices for accurate estimations. This is especially essential for low-resolution spectral observations. We provided calibrations for several ongoing or upcoming spectroscopic surveys such as the LAMOST low-resolution survey, the SEGUE survey, the SDSS-V/BOSS survey, the DESI survey, the MSE survey, and the MUST survey. Using common targets between the HARPS and MWO observations, we established conversions from spectral S-indices to the well-known SMWO values, applicable to stars with [Fe/H] values greater than −1. These calibrations offer a reliable approach to convert S-indices obtained from various spectroscopic surveys into SMWO values and can be widely applied in studies on chromospheric activity.
@article{arxiv.2503.20165,
title = {Impact of Spectral Resolution on S-index and Its Application to Spectroscopic Surveys},
author = {Henggeng Han and Song Wang and Xue Li and Chuanjie Zheng and Jifeng Liu},
journal= {arXiv preprint arXiv:2503.20165},
year = {2025}
}