  Like the solar cycle, stellar activity cycles are also irregular.
Observations reveal that rapidly rotating (young) Sun-like stars exhibit a high
level of activity with no Maunder-like grand minima and rarely display smooth
regular activity cycles. On the other hand, slowly rotating old stars like the
Sun have low activity levels and smooth cycles with occasional grand minima.
We, for the first time, try to model these observational trends using flux
transport dynamo models. Following previous works, we build kinematic dynamo
models of one solar mass star with different rotation rates. Differential
rotation and meridional circulation are specified with a mean-field
hydrodynamic model. We include stochastic fluctuations in the Babcock-Leighton
source of the poloidal field to capture the inherent fluctuations in the
stellar convection. Based on extensive simulations, we find that rapidly
rotating stars produce highly irregular cycles with strong magnetic fields and
rarely produce Maunder-like grand minima, whereas the slowly-rotating stars
(with a rotation period of 10 days and longer) produce smooth cycles of weaker
strength, long-term modulation in the amplitude, and occasional extended grand
minima. The average duration and the frequency of grand minima increase with
decreasing rotation rate. These results can be understood as the tendency of
less supercritical dynamo in slower rotating stars to be more prone to produce
extended grand minima
