Discipline: Astronomy
Research area: Stellar magnetism, spectropolarimetry
Context
The physics describing stars is becoming better understood. In particular, we understand better the importance of magnetic fields in the phases of star birth, mass loss processes and evolved phases. On the other hand, the observation of stellar magnetic fields, which is fundamental for testing models, is still in its infancy in 2015. It requires very fine expertise in spectro-polarimetry techniques. In the world, only a few instruments can make this type of measurement. This is the area in which the Bernard Lyot Telescope has specialized since the early 2000s. In 2015, it remains the only telescope in the world dedicated to the study of stellar magnetism. The latest generation instrument at its focus is Narval, twins of ESPADONS (at the focus of the Canada-France-Hawaii Telescope), designed by the team from the Institut de Recherche en Astrophysique et Planétologie (Toulouse) and the Midi Pyrénées Observatory. The Bernard Lyot Telescope is a National Observation Service of the Midi Pyrénées Observatory (University of Toulouse and National Institute of Universe Sciences of the CNRS).
Method and Operation of the installation
The Bernard Lyot Telescope is a Cassegrain type with a 50 m focal length, with a hydraulic equatorial cradle mount. Its characteristic dome is a zenithal cap and operculum, which served as a model for the dome of the Twenty Meter Telescope project (Hawaii). The motors of all components are controlled via a digital network. The temperature and humidity of the dome are controlled to maximize air stability. The telescope and its scientific instrumentation can be controlled remotely.
The Narval instrument is composed of a polarimeter at the focus of the telescope to control the movement of the telescope on the target star, to correct the effects of atmospheric refraction and to analyze the circular and linear polarization with a series of rhombohedrons and birefringent plates. The light thus analyzed is redirected by optical fibers from the polarimeter output to a very high-resolution spectrograph located 3 floors lower in a temperature-regulated box. It is the combination of polarization and spectroscopy that allows us to measure the magnetic fields on the surface of stars.
The observation time at the Bernard Lyot Telescope is reserved for the French and European community by competition. Astronomers no longer need to travel to the telescope. Observations are carried out by the TBL scientific team in service mode. All data collected during the night are cleaned and pre-analyzed before being made available to astronomers the next day via the internet.
Expected results
The Bernard Lyot Telescope with Narval has made a plethora of pioneering discoveries since 2007. Discovery of magnetic fields in massive fully convective stars, red giants (Betelgeuse, Pollux), A stars (Vega). Narval discovered short magnetic cycles (2 years) around “solar twin” stars where the solar cycle is 11 years. The first magnetic studies of exoplanetary systems have been made. Its studies of stellar magnetics on dwarf stars have shown the importance of dynamo processes in the creation of magnetic fields. The first studies of magnetic fields in protoplanetary disks have shown the potential of these measurements to understand the birth of planetary systems.
More than 400 articles have been published since the first observations with TBL/Narval (Hindex > 80).
The future of the post-Narval TBL is an expansion of Narval’s measurement capabilities towards the domain of exoplanets, with Neo-Narval and SPIP (Spectro-polarimeter Infrared at Pic du Midi).
