M dwarf planetary systems: an observational study to look for prolonged activity in host stars

M dwarf (dM) stars begin their lives rapidly rotating and with high levels of activity, but as time goes on, they slow down via magnetically channeled winds, whilst their activity decreases. We aim to investigate the possibility of prolonged rotation and activity in dMs due to tidal interaction with close-in planets, an effect previously observed for Sun-like stars with hot Jupiters by Poppenhaeger and Wolk (2014). We present some basic theoretical estimations on the strength of tidal forces raised by planets in ultracool dwarfs hosts and on the angular momentum exchanged between these systems. We are conducting a pilot survey of M dwarfs + white dwarf wide binary systems to study the age-activity relationship for M dwarfs by using the white dwarf as an age calibrator, a method that still remains biased against cool white dwarf components. We have identified a population of common proper-motion/distance binaries identified combining Gaia DR2 with our previously constructed SDSS/2MASS/WISE M dwarf catalogue (Cook et al. 2016). With this method we will significantly improve our understanding of the age-activity relation of older (> 1 Gyr) dMs and we will focus in possible over-active M dwarfs in our oldest systems, to look for hints of tidal interactions with planets.