The search for exocomets. Gas around main-sequence stars

The environment of main sequence stars is expected to be depleted of gas once they have left the protoplanetary disc phase. Thus, a replenishment mechanism, such as grain-grain collisions or evaporation of solid bodies, is required to explain the presence of gas recently reported to be present around some MS stars. Here, we present a high resolution spectroscopic survey of over 100 A to G stars, searching for gas in the form of stable and variable non-photospheric absorptions in metallic lines (mainly Ca II and Na I). The observations were carried out in both hemispheres at La Palma (Spain), La Luz (México) and La Silla (Chile) observatories. The over 2000 spectra obtained allow us to construct time-series for most of the stars in the sample. So far, we have found gas compatible with circumstellar origin in almost half of the sample, and variable absorptions which can be interpreted as the evaporation of solid bodies, i.e. exocomets, in several objects, some of them being new detections.