Characterising stellar and planetary magnetic fields via low-frequency radio astro
by Christene Lynch (Sydney University)
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.
(Image credit: NASA)