A Study of Stellar Gyrochronology by Using the PTF, LAMOST and Kepler K2 Data

Chang et al. 2016 showed that flare activities of the M dwarfs correlates with their corresponding chromospheric Ha emission by analyzing the LAMOST and Kepler K1 data. Stars with rotation periods shorter than 20 hours usually exhibit enhanced Ha emission and frequent occurrence of large flare events. To make a further understanding, we have initiated a project to estimate the Ha emission strength of M dwarfs using the Palomar Transient Factory (PTF) data archive and cross-correlating with LAMOST spectra. We have found a considerable amount of M dwarfs which are all included in the PTF Ha data archive and K2 catalog in some Campaigns of K2. We examine that if the PTF Ha photometric measurements can yield similar results as obtained in medium resolution spectral observations. Some interesting relationship between the equivalent width of Ha emission and Ha excess have been found.