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Experts in: Time series analysis, time variability

Lafrenière, David


Professeur agrégé

The study of exoplanets aims at establishing the prevalence and diversity of planetary systems in our galaxy, understanding how these systems form and evolve, comprehending the physics involved in their atmosphere and interior and, ultimately, detecting traces of life elsewhere in the universe. This is the main interest of Professor Lafrenière's group. The group's work is primarily performed using infrared imaging techniques that allow them to detect the planets directly, and then measuring their physical properties. To successfully "see" these very faint planets located right next to their host star, which can be several million times brighter, it is necessary to continually develop new observation and image processing techniques and even to build new instruments. With current technology, it is possible to detect gas giant planets with orbits of the outer solar system's size or larger.

In addition to direct imaging of planets, Professor Lafrenière's research group is also interested in the characterization of "hot Jupiter" planets by using transit/eclipse spectrophotometry and transit timing. The group is also involved in studies of brown dwarfs, in stellar and substellar multiplicity studies, and in searching for new young low-mass stars in the solar neighborhood.


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St-Louis, Nicole

ST-LOUIS, Nicole

Professeure titulaire

My research is mainly on the wind from the most massive stars. In view of their great luminosity - reaching one million times that of the Sun - these stars lose a large proportion of their mass over their lifetimes. This stellar wind is not symmetrical or homogenous. Not only does it contain small-scale inhomogeneities relating to turbulence, but in some cases also large-scale structures. These structures are particularly intriguing, since they are created by an as-yet unidentified mechanism occurring at the surface of the star.

The possible mechanisms include magnetic fields and pulses, two important physical processes in the evolution of massive stars, but about which we still have very little information.

The consequences of these large-scale structures for observable data (spectrum, photometry, polarization rate) can also help us to determine a fundamental parameter of these stars: their rotation velocity. This important detail is usually impossible to measure for the massive stars I am studying, since their surface is completely concealed behind the very dense wind. Because the large-scale structures are attached to the surface, identifying a period in the star's spectral or luminous variations lets us deduce the rotation velocity.


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