Stellar Chromospheric Activity Database of Solar-like Stars Based on the LAMOST Low-Resolution Spectroscopic Survey III. Calibrating the Chromospheric Basal Flux and the Connection to Stellar Rotation · arXivDesk
2603.03696Mar 4, 2026accepted for publication in ApJS
Stellar Chromospheric Activity Database of Solar-like Stars Based on the LAMOST Low-Resolution Spectroscopic Survey III. Calibrating the Chromospheric Basal Flux and the Connection to Stellar Rotation
Based on the Ca II H and K lines observed by LAMOST, we employ the photospheric (RHK′) and basal (RHK,L+
Nearby in the stack
) flux calibrated chromospheric activity indices to examine the relationship between chromospheric activity and the stellar rotation rate. We identify the rotation periods of 11,108 stars observed by Kepler and TESS by cross-matching our chromospheric activity catalog with previous studies. Our statistical results show that chromospheric activity increases with the rotation rate until it reaches a saturation level. As the stellar effective temperature increases from 4950 to 5850 K, the saturation values of the rotation period (
Prot
) vary correspondingly from 4.38 to 1.23 days for
RHK′
and from 9.88 to 1.33 days for
RHK,L+
. Similarly, the corresponding saturation Rossby number Ro ranges from 0.200 to 0.032 for
RHK′
and from 0.302 to 0.107 for
RHK,L+
. The saturation is also found to be significant in stars with thick convective zones, whereas it is less apparent in stars with higher effective temperatures. For solar-like stars in the
Teff
range of 4800 to 6000 K, The values of chromospheric activity indicators are saturated when