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SUMMARY:White Dwarf Planetary Systems: a window onto exoplanetary composit
 ion - Andrew Buchan (IoA)\, Laura Rogers (IoA)\, Chris Manser (Imperial)
DTSTART:20230131T130000Z
DTEND:20230131T140000Z
UID:TALK196654@talks.cam.ac.uk
CONTACT:Dr Emily Sandford
DESCRIPTION:Planetary systems around white dwarf stars are diverse and int
 riguing. Nearly 50% of single white dwarfs are polluted with exoplanetary 
 material\, and it is from this that the bulk composition of exoplanets can
  be inferred. It is hypothesised that this material originates from the ou
 ter planetary system\, gets perturbed onto highly eccentric orbits\, tidal
 ly disrupts forming a disc of dust and gas\, and then accretes. The key to
  understanding these enigmatic systems is through the accretion of the dus
 t and gas\, however\, only 4% show evidence for an observable circumstella
 r dust disc\, and more rarely\, 0.067% show evidence for an observable cir
 cumstellar gas disc. This talk will present the abundances of the planetar
 y material accreting onto a sample of white dwarfs with gas discs\, are th
 ere compositional differences? What can this tell us about how accretion p
 roceeds?\n\nWe will also present recent observations of these gaseous debr
 is discs\, which are mostly focused on line-emission from atomic transitio
 ns (most notably the 860nm Ca II triplet). We will show how these observat
 ions can be used to monitor the evolution of the gaseous components of the
 se discs\, and how velocity images can be generated using the method of Do
 ppler Tomography to better understand their structure. In particular we wi
 ll show velocity images for the gaseous discs around SDSSJ1228+1040 and HE
 1349–2305\, and observations of more gas discs from a recent X-Shooter m
 onitoring program.\n\nWhite dwarfs whose atmospheres are polluted by heavy
  metals provide a means to effectively dissect planetary material and meas
 ure the relative abundances of key rock-forming elements. These abundances
  can be understood in terms of the evolutionary history of planetary bodie
 s which have been recently accreted onto the white dwarf. We will describe
  how these abundances can be modelled\, using HE1349–2305 and SDSS1228+1
 040 as case studies. We will then place these results into the broader con
 text of white dwarf pollution\, discussing in particular the ubiquity of c
 ore-mantle differentiation in the galaxy.
LOCATION:Ryle seminar room + ONLINE - Details to be sent by email
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