Magnetospheric Radio Emission from Extrasolar Giant Planets: the Role of the Host Stars

We present a new analysis of the expected magnetospheric radio emission from extrasolar giant planets (EGPs) for a distance limited sample of the nearest known extrasolar planets. Using recent results on the correlation between stellar X-ray flux and mass-loss rates from nearby stars, we estimate the expected mass-loss rates of the host stars of extrasolar planets that lie within 20 pc of the Earth. We find that some of the host stars have mass-loss rates that are more than 100 times that of the Sun and, given the expected dependence of the planetary magnetospheric radio flux on stellar wind properties, this has a very substantial effect. Using these results and extrapolations of the likely magnetic properties of the extrasolar planets, we infer their likely radio properties. We compile a list of the most promising radio targets and conclude that the planets orbiting Tau Bootes, Gliese 86, Upsilon Andromeda and HD1237 (as well as HD179949) are the most promising candidates, with expected flux levels that should be detectable in the near future with upcoming telescope arrays. The expected emission peak from these candidate radio emitting planets is typically 40- 50 MHz. We also discuss a range of observational considerations for detecting EGPs.