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The Still-Perilous Fate of Planets and Asteroids that Survive Stellar Evolution

jjhermes
January 15, 2019

The Still-Perilous Fate of Planets and Asteroids that Survive Stellar Evolution

Conference presentation, 20 min. January 2019: Boston Area Exoplanet Science Meeting #5, Boston, MA, USA.

jjhermes

January 15, 2019
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  1. http://jjherm.es
    J.J. Hermes
    The Still-Perilous Fate of Planets and
    Asteroids that Survive Stellar Evolution

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  2. Today
    Boris Gänsicke

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  3. 5 billion years
    from now
    Boris Gänsicke

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  4. The life cycle of the Sun
    8 billion years
    from now
    Boris Gänsicke

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  5. Typical DA white dwarf log(g) = 8.0
    • Settling times << years
    • Radiative levitation inefficient <25,000 K
    • Expect pure hydrogen photospheres

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  6. DA white dwarf + metals
    But many
    white dwarfs
    show metals!

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  7. • Consensus: Metals are from accreted, tidally disrupted debris
    – 30-50% of all WDs are metal polluted when look in UV (Koester et al. 2014)
    – WD debris is comparable to bulk Earth (dominated by Fe, O, S, Mg)
    – Some of this debris is water-rich! (Farihi et al. 2013)
    WDs Directly Measure Exoplanet Compositions
    Abundances of rocks
    falling on 10
    different white dwarfs:
    Xu et al. 2014
    Bulk Earth
    Comet Halley

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  8. 1. We are observing the future of
    planetary systems around 2-3 solar-
    mass ZAMS stars.
    2. As the host evolves, the orbits of
    surviving planets expand. Objects
    destabilize, some scatter in.
    3. Ancient solar systems have
    leftover debris. We can see it if it
    pollutes a pristine white dwarf.

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  9. (a) Photospheric pollution
    (b) IR excess (dust disks)
    (c) Ca emission (gas disks)
    Farihi 2016
    Observational evidence of
    remnant planetary systems:

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  10. van Lieshout et al. 2018

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  11. (d) Transits of the white dwarf (WD1145+017)
    Gänsicke et al. 2016
    Vanderburg et al. 2015
    Mark Garlick
    4RWD
    model

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  12. van Sluijs & Van Eylen 2018
    >1100 white dwarfs observed by K2 through Campaign 13
    Only 1 (WD1145+017) shows transits
    (Gaia: 2113 bona fide WDs observed through K2 Campaign 18)

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  13. tasoc.dk
    175 white dwarfs observed (2-min) by TESS through Sector 2
    815 WDs in Cycle 1 with T<16 mag
    Expect >1400 WDs proposed in Cycle 2 (thanks Gaia!)
    T = 15.2 mag WD in Sector 2

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  14. Rowan et al. 2019, arXiv: 1812.05614
    >15,000 WDs with GALEX light curves longer than 10-min
    Still no new transits detected!
    (observed occurrence rate <0.5%)

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  15. Dennihy et al. 2018
    WD gas disks
    are incredibly
    dynamic
    Some disks show cyclic
    variations with periods
    <1.5 years!

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  16. Cauley et al. 2018
    Circumstellar gas
    absorption in
    WD1145+017 shows cyclic
    variations with few-year
    timescale

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  17. Manser et al. 2019, in review (no tweets, plz)
    evidence of "a solid
    body with significant
    internal strength"
    123.4-min periodic modulation of Ca II:

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  18. Mark Garlick
    30-50% of WDs are being
    actively polluted by rocks
    Few dozen show IR excess
    from dusty debris
    Less than a dozen show
    gas emission (Ca II)
    One (WD1145+017) shows
    transiting rocky debris
    No surviving, in-tact planets yet discovered:
    Gaia end-of-mission astrometry beckons!

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