Jean-François Donati

Learn More
We report here our spectropolarimetric observations obtained using the Es-padons/CFHT high resolution spectrograph of two M dwarf stars which standard models suggest are fully convective: EV Lac (M3.5) and HH And (M5.5). The difference in their rotational velocity makes them good targets to study the dependence of the magnetic field topology in M dwarfs on(More)
The magnetic field topology plays an important role in the understanding of stellar magnetic activity. While it is widely accepted that the dynamo action present in low-mass partially convective stars (e.g., the Sun) results in predominantly toroidal magnetic flux, the field topology in fully convective stars (masses below ∼ 0.35 M ⊙) is still under debate.(More)
Understanding how cool stars produce magnetic fields within their interiors is crucial for predicting the impact of such fields, such as the activity cycle of the Sun. In this respect, studying fully convective stars enables us to investigate the role of convective zones in magnetic field generation. We produced a magnetic map of a rapidly rotating,(More)
Models predict that magnetic fields play a crucial role in the physics of astrophysical accretion disks and their associated winds and jets. For example, the rotation of the disk twists around the rotation axis the initially vertical magnetic field, which responds by slowing down the plasma in the disk and by causing it to fall towards the central star. The(More)
We have used a doppler tomographic analysis to conduct a deep search for the starlight reflected from the planetary companion to HD 75289. In 4 nights on VLT2/UVES in January 2003, we obtained 684 high resolutionéchelle spectra with a total integration time of 26 hours. We establish an upper limit on the planet's geometric albedo p < 0.12 (to the 99.9%(More)
  • 1