Stellar Winds and Coronae in Cool Stars

Winds in R Coronae Borealis Stars

We present new spectroscopic observations of the He I λ10830 line in R Coronae Borealis (RCB) stars which provide the first strong evidence that most, if not all, RCB stars have winds. It has long been suggested that when dust forms around an RCB star, radiation pressure accelerates the dust away from the star, dragging the gas along with it. The new spectra show that nine of the ten stars obse...

Stellar Winds from Massive Stars

We review the various techniques through which wind properties of massive stars – O stars, AB supergiants, Luminous Blue Variables (LBVs), Wolf-Rayet (WR) stars and cool supergiants – are derived. The wind momentum-luminosity relation (e.g. Kudritzki et al. 1999) provides a method of predicting mass-loss rates of O stars and blue supergiants which is superior to previous parameterizations. Assu...

Mapping the Radio Coronae of Cool Stars and Brown Dwarfs

The pulsing radio emission detected from ultracool dwarfs can be used as a powerful diagnostic of magnetic field strengths and topologies at and below the substellar boundary. Studies thus far have confirmed magnetic field strengths of 3 kG for two late M dwarfs and 1.7 kG for an L3.5 dwarf, the latter being the first confirmation of kG magnetic fields for an L dwarf. Ongoing long term monitori...

Solar and Stellar Coronae

The existence of hot coronae throughout the HR diagram has been proved by the observations of the Einstein observatory since the late 1970's This nding has stimulated a new interest in the study of stellar activity. The general picture relating stellar activity in late type stars to the internal generation, photospheric emergence, and chromospheric and coronal dissipation of magnetic elds, was ...

Physics of Stellar Coronae