Pierre Bergeron is interested in the study of white dwarf stars, and more specifically in the calculation of atmospheric models. White dwarf stars represent the last evolutionary stage of more than 97% of the stars in our galaxy, including our Sun. Having exhausted the nuclear energy sources at their core, white dwarfs cool down quietly over periods of several billion years. They have a mass comparable to that of the Sun, but in a volume equal to that of the Earth, making them extremely compact objects with a density a million times that of the Sun.
Studying these stellar corpses and determining their fundamental parameters, such as temperature, mass and chemical composition, not only tells us about the nature of these stars, but also about their evolutionary links with the stars that spawned them. The most accurate way to measure the fundamental parameters of white dwarf stars is to compare detailed spectroscopic data – that is, the distribution of flux as a function of wavelength – with theoretical predictions obtained from atmosphere models, a method we’ve been refining for years at the Université de Montréal. A star’s atmosphere is the thin surface layer from which the radiation flux originates.
Pierre Bergeron is also interested in the study of variable white dwarf stars of the ZZ Ceti type, and more specifically in the empirical determination of the temperature limits of the instability band. His theoretical projects make use of photometric and spectroscopic data obtained at the various Kitt Peak observatories in Arizona (2.3 m Steward, 2.1 m and 4 m Kitt Peak) and at the Observatoire du Mont-Mégantic.