We are investigating the magnetic characteristics of pre-main sequence Herbig Ae/Be stars, with t... more We are investigating the magnetic characteristics of pre-main sequence Herbig Ae/Be stars, with the aim of: 1) understanding the origin and evolution of magnetism in intermediate-mass stars, and 2) exploring the influence of magnetic fields on accretion, rotation and mass-loss at the early stages of evolution of A, B, and O stars. We have begun by conducting 2 large surveys
We describe an ongoing observational programme, using the MuSiCoS spectropolarimeter at Pic du Mi... more We describe an ongoing observational programme, using the MuSiCoS spectropolarimeter at Pic du Midi Observatory, aimed at detecting the weakest magnetic fields of Ap/Bp stars. For the 21 stars observed up to now, we have obtained 19 detections of Stokes V Zeeman signatures. This remarkable detection rate strongly suggests that all Ap stars having "magnetic" behaviour (Preston 1974; i.e. essentially
Short-Term Spectroscopic Variability in the Pre-Main-Sequence Herbig Ae Star AB Aur During the MU... more Short-Term Spectroscopic Variability in the Pre-Main-Sequence Herbig Ae Star AB Aur During the MUSICOS 96 Campaign Claude Catala1, Jean-Francois Donati1, Torsten Bohm1, and the MUSICOS collaboration Observatoire Midi-Pyrenees, 14, avenue Edouard Belin, F-31400 ...
The spectra of a number of reportedly sharp-line B, A and F stars have been observed in a 60-Å wi... more The spectra of a number of reportedly sharp-line B, A and F stars have been observed in a 60-Å window with a resolving power of 120 000. As a first step in analysis of these data, the spectra have been synthesized to see how well simple models fit. The information obtained from both successful modelling and from discrepant fits is
The origin of magnetic fields of chemically peculiar main sequence Ap/Bp stars is still a matter ... more The origin of magnetic fields of chemically peculiar main sequence Ap/Bp stars is still a matter of intense debate. The recent discoveries of magnetic fields in Herbig Ae/Be stars using high resolution data obtained with the spectropolarimeter ESPaDOnS at CFHT provide a strong argument in favour of the fossil field hypothesis. Using a simple oblique rotator model of a centered dipole, we fit the Stokes V LSD profiles of two of these magnetic HAeBe stars, HD 200775 and V380 Ori, as well as their variations on timescales from days to months. We find that in both cases the dipole hypothesis is acceptable, and we determine the rotation period P, the angle between rotation and magnetic axes beta and the intensity of the magnetic field at the pole B_{P}.
We are investigating the magnetic characteristics of pre-main sequence Herbig Ae/Be stars, with t... more We are investigating the magnetic characteristics of pre-main sequence Herbig Ae/Be stars, with the aim of: 1) understanding the origin and evolution of magnetism in intermediate-mass stars, and 2) exploring the influence of magnetic fields on accretion, rotation and mass-loss at the early stages of evolution of A, B, and O stars. We have begun by conducting 2 large surveys
We describe an ongoing observational programme, using the MuSiCoS spectropolarimeter at Pic du Mi... more We describe an ongoing observational programme, using the MuSiCoS spectropolarimeter at Pic du Midi Observatory, aimed at detecting the weakest magnetic fields of Ap/Bp stars. For the 21 stars observed up to now, we have obtained 19 detections of Stokes V Zeeman signatures. This remarkable detection rate strongly suggests that all Ap stars having "magnetic" behaviour (Preston 1974; i.e. essentially
Short-Term Spectroscopic Variability in the Pre-Main-Sequence Herbig Ae Star AB Aur During the MU... more Short-Term Spectroscopic Variability in the Pre-Main-Sequence Herbig Ae Star AB Aur During the MUSICOS 96 Campaign Claude Catala1, Jean-Francois Donati1, Torsten Bohm1, and the MUSICOS collaboration Observatoire Midi-Pyrenees, 14, avenue Edouard Belin, F-31400 ...
The spectra of a number of reportedly sharp-line B, A and F stars have been observed in a 60-Å wi... more The spectra of a number of reportedly sharp-line B, A and F stars have been observed in a 60-Å window with a resolving power of 120 000. As a first step in analysis of these data, the spectra have been synthesized to see how well simple models fit. The information obtained from both successful modelling and from discrepant fits is
The origin of magnetic fields of chemically peculiar main sequence Ap/Bp stars is still a matter ... more The origin of magnetic fields of chemically peculiar main sequence Ap/Bp stars is still a matter of intense debate. The recent discoveries of magnetic fields in Herbig Ae/Be stars using high resolution data obtained with the spectropolarimeter ESPaDOnS at CFHT provide a strong argument in favour of the fossil field hypothesis. Using a simple oblique rotator model of a centered dipole, we fit the Stokes V LSD profiles of two of these magnetic HAeBe stars, HD 200775 and V380 Ori, as well as their variations on timescales from days to months. We find that in both cases the dipole hypothesis is acceptable, and we determine the rotation period P, the angle between rotation and magnetic axes beta and the intensity of the magnetic field at the pole B_{P}.
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Papers by J. Landstreet