Disentangling stellar activity from planet signals

Despite the advent of larger telescopes and improved instrumentation, the search for smaller Earth-like planets in the habitable zone is largely deterred by the presence of stellar jitter in the radial velocity (RV) data. This stellar jitter or activity can introduce signals in the RV data with periods ranging from days (rotation) to years (activity cycles). There have been planets discovered that were later refuted due to stellar activity. In my talk, I will discuss ways on how to filter this jitter to help detect smaller planets. I will talk about the activity indicators that coincide with periodic signals in RV and photometry data and different ways to disentangle these signals so that true planet signals with low amplitudes can be detected. Further, I will briefly talk about the multi-wavelength studies of flare stars to assess stellar activity in different wavelength regions. Such studies offer possible clues to the erosion of planetary atmosphere in the early years of planet formation by stellar irradiation in the X-ray and ultraviolet wavelength regime (XUV).