Christene Lynch (Sydney University)

Christene Lynch colloquium: Characterising stellar and planetary magnetic fields via low-frequency radio astro

Abstract

Establishing what criteria define habitability is essential for determining the potential for life outside the Solar System. Traditionally, a planet is considered habitable if it is orbiting within the circumstellar region that makes possible the existence of liquid water on the planet’s surface. However, an equally important factor in determining habitability is the stability of a planet’s atmosphere, which regulates its surface temperature. Intense stellar magnetic activity, such as flares and wind, can erode the planet’s atmosphere, leaving the planet uninhabitable. Strong planetary magnetic fields may mitigate the impact of the stellar magnetic activity. Thus to evaluate a planet’s habitability, the magnetic fields of both star and planet must be considered. M dwarf stars are of particular interest as they are currently favoured as most likely to host habitable, nearby exoplanets. Yet the extreme magnetic activity observed for some M dwarf stars places some doubt on the ability of orbiting exoplanets to host life. Radio observations uniquely provide direct measurements of the magnetic field strengths associated with stars and planets. New wide-field, low frequency radio telescopes will probe a frequency regime that is mostly unexplored for many magnetically active stars and where exoplanets are expected to produce radio emission. This presentation reports the first results from a targeted Murchison Widefield Array survey of M dwarf stars that were previously detected at 100 - 200 MHz using single dish telescopes. I will discuss robust flare-rate measurements over a high dynamic range of flare properties, as well as investigate the physical mechanism(s) behind the flares. I will also present the results of low-frequency observations of young, hot Jupiter systems; these systems are hypothesised to be the best candidates for radio detections with the current suite of low-frequency telescopes.