Detection of Exocomets: The gaseous environment of Main-Sequence Stars

Planetesimals and small solid bodies in general  are key to understand the chemical and dynamical evolution of planetary systems. Direct detection outside the Solar System is still not feasible. However, indirect evidences of such bodies as dusty debris disks or the presence of large amounts of gas in the close-in surroundings of main-sequence stars have been collected for over 30 years now.

Transient events observed as variable non-photospheric spectral features in metallic lines were first detected in $\beta$-Pictoris and attributed to outgassing of solid bodies grazing or falling onto the stars, i.e. exocomets. Since then, only around 20 stars have been found to show variable features reminiscent of the  $\beta$-Pictoris exocomets..

Here I present the results of a large high-resolution spectroscopic survey aiming at detecting and monitoring the presence of exocomets around main sequence stars.  Over 2000 spectra from more than 100 AFG-type stars have been obtained in observatories from both Hemispheres. The objective is to construct time series for each star in order to detect transient features in their metallic lines (mainly Ca II and Na I) which could be originated by exocomets in the immediate stellar environment. We have found gaseous absorption features compatible with a circumstellar origin in ~25% the sample, and variable absorptions in 18 objects, being some of them new detections. Our results allow us to link the presence of small solid bodies to the physical characteristics of the star or its environment.

12/09/2019 - 12:30
Dr. Isabel Rebollido
Universidad Autónoma de Madrid