Radio emission from hot stars and planets

[摘要] The winds of hot massive stars and hot giant planets grant us insight into the mechanisms by which the interstellar medium is enriched and the history behind planetary system formation. This thesis comprises a series of studies investigating the magnetospheric dynamics and emission properties of both these astronomical bodies. An analytic study of thermal radio and sub-mm emission from the winds of massive stars investigates the contribution from acceleration and wind clumping. The results show strong variation of the spectral index, corresponding to the wind acceleration region and clumping of the wind. This shows a strong dependence of the emission on the wind velocity and clumping profile. By performing simulations of a magnetic rotating massive star with a non-zero dipole obliquity, it has been shown that the predicted radio and sub mm observable light curves and continuum spectra are highly dependent on the magnetic confinement of the stellar wind close to the surface, and that understanding the observer inclination and magnetic dipole obliquity are vital for determining the stellar mass-loss rate from radio observations. Hot Jupiter exoplanets are expected to produce strong radio emission in the MHz range but have not been detected. To explain the absence of observational results, simulations of the interactions between a solar type star and hot Jupiter were conducted and used to calculate the efficiency of radio emission generation within the planet's magnetosphere. Results show that it is completely inhibited by the planet's expanding atmosphere. Finally, the first simulations of wind-wind interactions between a solar type star and a short period hot Jupiter exoplanet that resolves accretion onto the surface of the star are presented. The accretion point, rate and periodicity are quantified, with the results indicating that material accreting onto the star perturbs surface density and temperature in a periodic manner, in agreement with observations.

[发布机构] University:University of Birmingham;Department:School of Physics and Astronomy

[关键词] Q Science;QB Astronomy