SO Webloquio: Auroral Radio Emission in stars and exoplanetary systems

In recent years, an interesting type of coherent radio emission has been detected in a wide variety of stars across the HR diagram, from hot magnetic A-B MS stars to Ultra Cool dwarfs: the Auroral Radio Emission (ARE), previously observed by spacecrafts in the magnetosphere of planets of the Solar System. Very different objects are showing the same phenomenon. What do they have in common? The first star with ARE was CU Virginis, an early type magnetic star with a tilted dipolar magnetic field, well described by the Oblique Rotator Model (ORM). Gyrosynchrotron radio emission, due to the interaction between the radiatively driven stellar wind and the magnetic field, is modulated by rotation. During observational campaigns aimed at testing a 3D model, we detected intense peaks of emission with the characteristics of Electron Cyclotron Maser (ECME), originating above the poles. They are visible as a radio lighthouse, in a pulsar-like fashion. In few words, Auroral Radio Emission. Later, ARE has been detected in other hot stars. The signature of highly beamed broad band ARE was clearly identified in many very low mass stars and brown dwarfs. The common ingredient is the presence of large-scale axisymmetric magnetic field, that allow us to use the same model developed for hot stars. We proposed that ARE in low mass star can be due to Star-Planet Interaction (SPI), as in the case of the interaction between Jupiter and its major satellites, and can be explained with the same model used for hot stars. The research for ARE in exoplanetary systems begun, and now there is a clear evidence that in the system of Proxima Cen it occurs. The model we developed for the ARE well accounts for the observations, opening new opportunity in the field of the search for life in exoplanets.

10/06/2021 - 12:30
Dr. Corrado Trigilio
Osservatorio Astrofisico di Catania (INAF-OACT)