Simulation of spot behavior on the Seven Sisters (Pleiades): do we mislead by K2 lightcurves?

As the most common feature on the stellar surface, starspots with cooler temperature are formed following stellar magnetic field activities. The spot events on young M dwarf stars are particularly strong due to their convective stellar envelope, which results in significant stellar variability and luminosity spread. These variabilities bias the estimation of stellar parameters through pre-main-sequence evolution tracks on H-R diagram. Observed by K2, the spot behavior of 125 Myr old young cluster Pleiades is detected by the frequency and amplitude of the lightcurves. However, the realistic information of spots is partially hidden by their symmetric or circumpolar morphologies. In this paper, we modeled the photometric variability introduced by randomly distributed stellar spots on a 125 Myr old star cluster. From the simulated lightcurves, we find that the observed spot activity is only 10% to 40% of the total spot event. Besides, the empirical color-color diagram (Pecaut+2013) can also be well reconstructed by spot covered photospheric models (Baraffe+2015). By fitting the footprints of spot covered clusters on H-R diagrams through pre-main-sequence evolution tracks, we found a 30% age spread is introduced by the underestimation of spot coverage. 

Speaker: 
Guo Zhen
Location: 
1st Seminar Room, KIAA-PKU
Time: 
Friday, April 13, 2018 - 5:00pm to 6:00pm