Pre-main sequence (PMS) stars typically have short rotation periods of a few days. They are known to power strong magnetic fields with the geodynamo effect, which subsequently dictates stellar accretion and launch of the magnetocentrifugal winds/jets. In addition, the luminous X-ray and UV feedback from these magnetic structures (e.g., loops) may dramatically affect the protoplanetary disk mass-dispersal and the formation/evolution of prebiotic molecules, which are crucial aspects for the understanding of the origin of life. Similar to the monitoring of sunspots over solar cycles, the diagnostics of the activities of the colossal cold spots on the PMS stars will provide invaluable information about these magnetic activities on the PMS stars. Thanks to the Kepler K2 and TESS mission, it has only recently become possible to perform long-duration (e.g., a few tens of days) monitoring observations to characterize the activities associated with cold spots without interruption.
In this work, we studied the activity on the stellar surface of DM Tau, one of the PMS stars, using the light curves obtained with the Kepler K2 and optical and near-infrared photometric monitoring observations. Periodic analysis of the K2 data shows that DM Tau spins for a period of 7.3 days. In addition, we found that nearly 50% of the surface of the host protostar is occupied by cold spots that are several hundred Kelvin cooler than the warmer side. We report on the results of the analysis of these optical observations, along with data obtained by the JVLA. The latter, which is tracing the ionized gas in the protoplanetary disk, seems to show variability on a timescale that is similar to what we found from the optical data.