A large proportion of observed white dwarfs show evidence of debris disks, remnants of the former planetary systems, and/or signatures of heavy elements in their atmospheres, induced by the accretion of planetary matter onto their surfaces. The observed abundances are the result of the balance between the accretion flux and the dilution of this planetary material by internal transport processes. The efficiency of internal processes are different depending on the white dwarf (DA hydrogen white dwarfs or DB helium white dwarfs). In this presentation, we show how the internal dilution processes, including thermohaline convection, can affect the inferred accretion rates, hence the retrieval of the properties of the accreted matter. Moreover, a recent study showed that more massive DA white dwarfs are less polluted than smaller mass ones. We show that the differences in observed heavy element pollution in white dwarfs according to their masses cannot be explained by the dilution induced by atomic diffusion and thermohaline mixing alone. It may suggest that the reason for this pollution difference according to the mass of the WDs is related to the formation of planetary systems when these stars were on the main sequence.
[Postponed] Linking the chemical composition of stars and exoplanets : Accretion signatures on white dwarfs
Mardi 14 avril 2026
de
14:00 à
15:00
Conference room, building 17
