Érika Le Bourdais (Université de Montréal)

LSPM J0207+3331: The first highly polluted cool hydrogen-rich white dwarf

Polluted white dwarfs serve as unique laboratories to study the bulk composition of exoplanetary material. As the remnants of the once complete planetary system orbit the dead star, parts can get trapped in the powerful gravitational field of the white dwarf and form a debris disk. The material will eventually disintegrate and accrete in the star’s pristine hydrogen or helium atmosphere, polluting the white dwarf. While the field focuses mostly on warm (10,000 K < Teff < 25,000 K) helium-rich white dwarfs because the conditions are optimal for detecting metal pollution, I will report on the discovery of the first highly polluted cool (Teff=5910 K) hydrogen-rich white dwarf: LSPM J0207+3331. I will present various results ranging from the impact of metals on determining the physical parameters of cool white dwarfs in the near infrared to the bulk composition of the parent body polluting this white dwarf. This discovery demonstrates that planetary systems can maintain massive enough reservoirs of planetary material to sustain the pollution of a white dwarf billions of years after the death of its progenitor.

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