Search for exoplanets and brown dwarfs with VLBI

TL;DR

This paper investigates the potential for detecting radio GHz emissions from exoplanets and brown dwarfs using VLBI, based on magnetic field strengths and emission mechanisms similar to Jupiter.

Contribution

It estimates radio emission flux densities from hypothetical young planetary systems and assesses their detectability with current VLBI technology.

Findings

Stellar wind-induced emission may be detectable by VLBI.

Magnetic fields in young massive planets could produce GHz emissions.

Emission from moon interactions is less efficient than stellar wind interactions.

Abstract

The main aim of this work is to estimate possible radio GHz emission of extrasolar planets and brown dwarfs and to check if such radiation can be detected by Very Large Baseline Interferometers (VLBI). In the estimation we assume that the emission may originate in processes similar to those observed in the Jupiter system. The frequency of the radio emission that is produced in this system depends mostly on the magnetic field strength. Jupiter's magnetic field ($\sim 9$ G on average) allows for radiation from kHz frequencies up to 40 MHz. This is well below the frequency range of VLBI. However, it was demonstrated that the magnetic field strength in massive and young object may be up to two orders of magnitude higher than for Jupiter, which is especially relevant for planets around short-lived A type stars. This should extend the range of the emission up to GHz frequencies. We calculated expected flux densities of radio emission for a variety of hypothetical young planetary systems. We analysed two different emission scenarios, and found that the radiation induced by moons (process similar to Jupiter-Io interactions) appears to be less efficient than the emission generated by a stellar wind on a planetary magnetosphere. We also estimated hypothetical emission of planets and brown dwarfs located around relatively young and massive main sequence A-type stars. Our results show that the emission produced by stellar winds could be detected by currently operating VLBI networks.