On the formation, evolution, and destruction of minor planetary bodies.

Thomas WilsonJonathan Rawling, Jay Farihi, Bruce Swinyard (UCL)

Ovidiu Vaduvescu (ING)

Outline

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Formation● Modelling the Origin of O2 in Comet 67P

Evolution● Herschel Observations of Non-Typical

Cometary Water Ortho-to-Para Ratios

Destruction● White Dwarf Planetary Debris Disks

Frequencies● Planetesimal Debris Disk Variation

Other projects I have worked on:Near-Earth Asteroids, Carbon-dominant white dwarfs, dwarf-Carbon stars.

Herschel Observations of

Non-Typical Cometary Water Ortho-to-Para

Ratios3

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Why study comets???

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Water, water everywhere

Bockelée-Morvan et al. 2004

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Using isotopic ratios as a proxy for formation location

Altwegg et al. 2015

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Observing water in the sub-millimetre

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Ortho-to-Para Ratio (OPR) as a function of temperature

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Ortho-to-Para Ratio should always be 3...

Hama et al. 2016

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H2O and NH3 Ortho-to-Para ratios

Shinnaka et al. 2016

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Herschel/SPIRE Observations

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Observations show multiple rotational lines

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Observations show an OPR less than 3...

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Observations show an OPR less than 3...

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… and OPR seems to vary with nucleocentric distance

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Conclusions

White Dwarf Planetary Debris

Disks Frequencies

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Exoplanet Zoo

Kaltenegger 2017

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Planetesimal debris disks around white dwarfs!

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Disrupted planets form disks which accretes onto the star

Jura & Young 2014

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(Exo)planetary compositions

Xu 2014

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GD 362

Xu 2014

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WD 1425+540

Xu et al. 2017

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Water, water everywhere? in GD 61

Farihi et al. 2013

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How do we find debris disks? - Atmospheric metals

van Maanen, 1917 Farihi 2016

Ca II H & K

v Ma 2

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How do we find debris disks? - Infrared excess

Zuckerman & Becklin 1987

G29-38

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Our unbiased samples

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The complete sample

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What do we know so far?

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Why do we see this? - Modeling

Mustill et al. 2014

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A white dwarf with an infrared excess...

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… and atmospheric metalsWD 1018+410

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Some white dwarfs show metals, but no infrared excess

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Infrared excess frequencies are a few percent...

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… but, the nominal atmospheric metals frequency is 47%!

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Conclusions● The only unbiased Spitzer and Hubble single hydrogen dominated white dwarf

sample over a large temperature/age range.

● 3 out of 206 stars have an infrared excess, yielding a frequency of 1.5%, whereas 61 out of 130 stars have atmospheric metals, roughly 47%.

● A significant percentage of debris disks still remain unobserved via infrared excesses.

The end

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Formation● Modelling the Origin of O2 in Comet 67P

Evolution● Herschel Observations of Non-Typical

Cometary Water Ortho-to-Para Ratios

Destruction● White Dwarf Planetary Debris Disks

Frequencies● Planetesimal Debris Disk Variation

Other projects I have worked on:Near-Earth Asteroids, Carbon-dominant white dwarfs, dwarf-Carbon stars.

Thanks for listening.

Any questions?

Extra slides

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Modelling the Origin of O2 in

Comet 67P

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Detection of O2 in Comet 67P

Bieler et al. 2015

Planetesimal Debris Disk

Variation

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WD 0959-0200 - The first variable disk

Xu & Jura 2014

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GD 56 - A highly variable disk

Farihi et al. 2018

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GD 56 - A highly variable disk

Farihi et al. 2018

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SDSS 1228

Xu et al. 2018