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SUMMARY:Post-main sequence thermal evolution of planetesimals: Implication
 s on white dwarf pollutants - Yuqi Li 
DTSTART:20231101T131500Z
DTEND:20231101T134000Z
UID:TALK207817@talks.cam.ac.uk
CONTACT:Hannah Uebler
DESCRIPTION:White dwarfs that have accreted planetary materials provide a 
 powerful tool to probe the interiors and formation of exoplanets. In parti
 cular\, the high Fe/Si ratio of some white dwarf pollutants suggests that 
 they are fragments of bodies that were heated enough to undergo large-scal
 e melting and iron core formation. In the solar system\, this phenomenon i
 s associated with bodies that formed early and so had short-lived radionuc
 lides to power their melting\, and/or grew large. However\, if the planeta
 ry bodies accreted by white dwarfs formed during the (pre)-main sequence l
 ifetime of the host star\, they will have potentially been exposed to a se
 cond era of heating during the star’s giant branches. This work aims to 
 quantify the effect of stellar irradiation during the giant branches on pl
 anetary bodies by coupling stellar evolution to thermal and orbital evolut
 ion of planetesimals. We find that large-scale melting\, sufficient to for
 m an iron core\, can be induced by stellar irradiation\, but only in close
 -in small bodies: planetesimals with radii ≲ 30 km originally within ∼
  2 AU orbiting a 1–3 𝑀⊙ host star with solar metallicity. Most of t
 he observed white dwarf pollutants are too massive to be explained by the 
 accretion of these small planetesimals that are melted during the giant br
 anches. Therefore\, we conclude that those white dwarfs that have accreted
  large masses of materials with enhanced or reduced Fe/Si remain an indica
 tor of planetesimal’s differentiation shortly after formation\, potentia
 lly linked to radiogenic heating.
LOCATION:The Hoyle Lecture Theatre + Zoom 
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