Work

The evolution of rotation and activity for FGK dwarfs in LAMOST– Kepler field

Year: 2025

Type: article

Abstract: ABSTRACT Based on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) and Gaia surveys, we compute the convective turnover time-scales of stars with the mass range of 0.7–1.4 ${\rm M}_{\odot }$ using the mesa code. We provide a catalogue of 10 400 FGK dwarfs in the LAMOST–Kepler field, including Rossby number Ro, rotation periods ${ P}_{\rm rot}$, photometric activity proxy $S_{\rm ph}$, and chromospheric activity index $R^{+}_{\rm HK}$. The relations between both activity indices and Ro can be characterized by the saturated, decay, and flat regimes. In the flat regime, the $S_{\rm ph}$ remains nearly constant while the $R^{+}_{\rm HK}$ exhibits an enhancement as Ro increases for F dwarfs. In the decay regime, all stars exhibit uniform decay behaviour in both $S_{\rm ph}$–Ro and $R^{+}_{\rm HK}$–Ro relations. In the saturated regime, GK dwarfs display a significant $S_{\rm ph}$ dip, while only K dwarfs exhibit a pronounced $R^{+}_{\rm HK}$ dip. Moreover, the Ro range of this dip aligns with the spin-down stalling observed in open cluster studies, suggesting a possible origin in the core–envelope coupling senario. Additionally, the results show that the Sun falls within the transition from decay to flat regime in both activity-Ro diagrams. The results will improve the understanding of the connection among convection, rotation, and magnetic fields for solar-like stars.

Source: Monthly Notices of the Royal Astronomical Society

DOI: 10.1093/mnras/staf1792