3 papers
astro-ph.SR2026
Six decades of TIGRE and Mount Wilson chromospheric monitoring in the H and K lines: The quest for an understanding of solar-type activity
J. H. M. M. Schmitt, K. -P. Schröder, M. Mittag +3
The combined time series of the consistently calibrated chromospheric activity indicator, the S-index -- derived from Mount Wilson and TIGRE data -- now spans more than five decade…
astro-ph.SR2026
On the stellar parameter dependence of the combined Fe I and Fe II chromospheric emission-line in the wings of the Ca II K line
Faiber Rosas-Portilla, Luis Zapata, Klaus-Peter Schröder +3
We present an analysis of the chromospheric emission of Fe I + Fe II in the wing of the Ca II K line of 21 G and K giant stars. Stellar parameters and absolute chromospheric fluxes…
astro-ph.SR2024
Relationship between TIGRE solar S-index and USET Ca II K full disk images
G. Vanden Broeck, S. Bechet, F. Clette +3
Full disk observations of the solar chromosphere in the Ca II K line represent a valuable dataset for studies of solar magnetic activity. The S-index is widely used to investigate…