| Abstract : | Pre-main-sequence (PMS) stars are known to be variables. Several mechanisms are known to induce these variabilities, for example, irregular distribution of cool spots on the stellar photosphere, variable hot spots, obscuration from dust instability in disk, change in accretion rate, pulsations, etc. The evolution of disks and the accretion rates play a prominent role in the non-periodic variability whereas the presence of cool and hot spots on the photosphere, rotation of the stars may produce periodic/quasi-periodic changes in their light curves. The period of the light curve of a rotating star is the direct indicator of its rotation period. In this work, we are studying the variability properties of stars in a sample of young star clusters in our Galaxy. With the help of the HR diagram of these clusters, we can constrain the physical parameters such as age and mass of PMS variable stars and it is easy to check the correlation between variability period and amplitude with different physical parameters (age, mass,accretion rate, etc.). Period of the PMS periodic variables ranges from a few hours to 15-20 days while amplitude ranges from 0.05 mag to 2 mag. The amplitude of variables increases with IR excess whereas the rotation speed seems to slow down with IR excess. Both the period and amplitude are found to decrease with increase in mass. We will show the results of a cluster obtained in our study. |
