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Improved white dwarf cooling ages using asteroseismology and eclipsing binaries

jjhermes
September 21, 2017

Improved white dwarf cooling ages using asteroseismology and eclipsing binaries

Conference presentation, 15 min. Sept. 2017: Ages^2: Taking Stellar Ages to the Next Power, Isola de Elba, Italy.

jjhermes

September 21, 2017
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  1. http://jjherm.es
    J.J. Hermes
    Hubble Fellow
    University of North Carolina
    at Chapel Hill
    Improved white dwarf cooling
    ages using asteroseismology
    and eclipsing binaries

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  2. Star Trek writer James Blish
    put planet Vulcan in orbit
    around 40 Eri A

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  3. Star Trek writer James Blish
    put planet Vulcan in orbit
    around 40 Eri A
    The age of 40 Eri A is
    ~1.8 Gyr

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  4. Star Trek writer James Blish
    put planet Vulcan in orbit
    around 40 Eri A
    The age of 40 Eri A is
    ~1.8 Gyr
    40 Eri, S. Smith

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  5. 40 Eri, S. Smith
    Star Trek writer James Blish
    put planet Vulcan in orbit
    around 40 Eri A
    40 Eri B: coeval white dwarf
    with total age ~1.8 Gyr
    I have evolved
    telepathy in
    less than 2
    billion years…

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  6. Bond, Bergeron & Bédard 2017, arXiv: 1709.00478
    0.573±0.018 M¤
    17,200±110 K
    WD Cooling Age: ~122 Myr
    +
    Cluster-Calibrated Initial-to-Final
    Mass Relation (Kalirai’s talk):
    1.8 M¤
    Progenitor:
    ~1.7 Gyr MS age
    40 Eri, S. Smith
    ~35 AU
    ~400 AU
    Thin
    H-layer
    Thick
    H-layer
    Precision mass-radius
    measurements can constrain
    envelope masses
    à Better cooling ages
    (Dynamical)
    (Parallax)
    40 Eri B
    Total Age ~1.8 Gyr

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  7. WD+dM Eclipsing Binaries: <2% WD Masses, Radii
    High-precision study of 16 detached WD+dM using X-shooter
    (double-lined velocities) + ULTRACAM (scaled radii)
    Steven Parsons et al. 2017, MNRAS, 470, 4473

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  8. WD+dM Eclipsing Binaries: <2% WD Masses, Radii
    No evidence for very thin
    H layers in 13 white dwarfs
    in close WD+dM binaries:
    All have <10-8 MH
    /M
    Parsons et al. 2017, MNRAS, 470, 4473
    He-core models
    C/O-core
    models
    Thick H (10-4)
    Thin H (10-10)

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  9. Asteroseismology: Pulsations Constrain Envelope Masses
    Detailed study of two superficially similar
    pulsating WDs: GD 165 and Ross 548
    Noemi Giammichele et al. 2015, ApJ, 815, 56
    Time (s)
    Rel. Flux
    Rel. Flux
    Both white dwarfs have
    Teff
    ~ 12,100 K and are ~0.64 Msun
    but quite different pulsation properties

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  10. Asteroseismology: Pulsations Constrain Envelope Masses
    Thick H Layer: 10-4.23±0.15 MH
    /M
    He Layer: 10-1.70±0.13 MHe
    /M
    Giammichele et al. 2016, ApJS, 223, 10
    Thin H Layer: 10-7.45±0.12 MH
    /M
    He Layer: 10-2.92±0.10 MHe
    /M

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  11. Asteroseismology: Pulsations Constrain Envelope Masses
    Thick H Layer: 10-4.23±0.15 MH
    /M
    He Layer: 10-1.70±0.13 MHe
    /M
    Giammichele et al. 2016, ApJS, 223, 10
    Thin H Layer: 10-7.45±0.12 MH
    /M
    He Layer: 10-2.92±0.10 MHe
    /M
    Ross 548 (thinner envelopes) cools ~25% more slowly
    than GD 165 (assuming identical core composition)

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  12. Original Kepler Mission (4 years):
    Just 20 white dwarfs observed,
    6 pulsating WDs (just two >3 months)
    K2 through Campaign 13:
    >1200 white dwarf candidates observed
    53 more pulsating WDs
    K2 has given us hundreds of
    candidate pulsating white
    dwarfs to observe

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  13. l = 2
    l = 2
    l = 1
    l = 1
    SDSSJ0106+0145, K2 Campaign 8
    Hermes et al. 2017, ApJS, in press; k2wd.org
    K2 is giving us exceptional data for WD
    asteroseismology
    k
    k = Number of radial nodes
    l = Number of vertical nodes
    m = Number of horizontal + vertical nodes

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  14. Asteroseismology: Insights from the Aggregated Periods
    Chris Clemens, Bart Dunlap et al. 2017, in prep.
    239 periods from 75 hot DAVs (mostly ground-based)
    Histogram of periods
    0
    5
    10
    15
    20
    25
    30
    50 100 150 200 250 300 350 400 450 500
    0
    5
    10
    15
    20
    25
    30
    50 100 150 200 250 300 350 400 450
    Mode Amplitude (ppt)
    N
    Mode Period (s)
    Mode Period (s)

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  15. Asteroseismology: Insights from the Aggregated Periods
    If we only plot identified l=1 modes:
    0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    l = 1
    k = 1
    l = 1
    k = 2
    l = 1
    k = 3
    Kepler makes mode identification relatively trivial
    Mode Period (s)
    N
    Clemens et al. 2017, in prep.
    SDSSJ0051+0339, g=17.6, K2 Campaign 8
    k2wd.org
    k = 1 k = 2 k = 3 k = 4

    View full-size slide

  16. Asteroseismology: Insights from the Aggregated Periods
    If we only plot identified l=1 modes:
    0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    Kepler makes mode identification relatively trivial
    Mode Period (s)
    N
    Clemens et al. 2017, in prep.
    l = 1
    k = 1
    l = 1
    k = 2
    l = 1
    k = 3
    k = 1 k = 2 k = 3 k = 4

    View full-size slide

  17. Asteroseismology: Insights from the Aggregated Periods
    If we only plot identified l=1 modes:
    0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    Kepler makes mode identification relatively trivial
    Mode Period (s)
    N
    k = 1 k = 2 k = 3 k = 4
    Clemens et al. 2017, in prep.
    l = 1
    k = 1
    l = 1
    k = 2
    l = 1
    k = 3

    View full-size slide

  18. Asteroseismology: Insights from the Aggregated Periods
    Clemens et al. 2017, in prep.
    0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    l=1 hDAV periods, observed
    Full evolutionary models computed
    by Alejandra Romero et al.
    2012, MNRAS, 420, 1462

    View full-size slide

  19. Asteroseismology: Insights from the Aggregated Periods
    Clemens et al. 2017, in prep.
    Drawing from a random distribution of
    models with a range of thick (10-4 MH
    /M
    )
    to thin (10-10 MH
    /M
    ) hydrogen layer
    masses, using the measured spectroscopic
    Teff
    & masses for each pulsating WD
    Full evolutionary models computed
    by Alejandra Romero et al.
    2012, MNRAS, 420, 1462
    0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    l=1 hDAV periods, observed
    0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    l=1 random MH
    simulation

    View full-size slide

  20. Asteroseismology: Insights from the Aggregated Periods
    Clemens et al. 2017, in prep.
    0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    l=1 hDAV periods, observed
    0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    l=1 random MH
    simulation
    l=1 canonical MH
    simulation
    Full evolutionary models computed
    by Alejandra Romero et al.
    2012, MNRAS, 420, 1462
    Only drawing from
    the models with
    canonically thick MH

    View full-size slide

  21. Asteroseismology: Insights from the Aggregated Periods
    Clemens et al. 2017, in prep.
    0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    l=1 hDAV periods, observed
    0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    l=1 random MH
    simulation
    l=1 canonical MH
    simulation
    Full evolutionary models computed
    by Alejandra Romero et al.
    2012, MNRAS, 420, 1462
    Only drawing from
    the models with
    canonically thick MH
    *The majority of WDs have
    canonical (thick) envelopes*

    View full-size slide

  22. Asteroseismology: Insights from the Aggregated Periods
    Clemens et al. 2017, in prep.
    size = amplitude
    of mode

    View full-size slide

  23. Asteroseismology: Insights from the Aggregated Periods
    Clemens et al. 2017, in prep.
    Ross 548
    GD 165
    l = 1, k = 2 l = 1, k = 1
    Thick H Layer: ~10-4 MH
    /M
    He Layer: ~10-1.7 MHe
    /M
    “Canonical” nuclear burning
    sets envelope masses
    Thin H Layer: <10-7 MH
    /M
    ~He Layer: 10-2.9 MHe
    /M
    Very late thermal pulses?
    Giammichele et al. 2016, ApJS, 223, 10
    size = amplitude
    of mode

    View full-size slide

  24. Asteroseismology: Insights from the Aggregated Periods
    Clemens et al. 2017, in prep.
    Ross 548
    GD 165
    l = 1, k = 2 l = 1, k = 1
    Thick H Layer: ~10-4 MH
    /M
    He Layer: ~10-1.7 MHe
    /M
    “Canonical” nuclear burning
    sets envelope masses
    Thin H Layer: <10-7 MH
    /M
    ~He Layer: 10-2.9 MHe
    /M
    Very late thermal pulses?
    Interpulse interaction?
    Giammichele et al. 2016, ApJS, 223, 10
    size = amplitude
    of mode
    ~80% of DAs have canonically thick (~10-4 MH
    /M
    ) envelopes
    ~20% of DAs have thinner (~10-7-9 MH
    /M
    ) envelopes
    à WDs with 1 dex thinner He envelopes cool >10% slower!
    N = 14 N = 4

    View full-size slide

  25. Asteroseismology: Insights from the Aggregated Periods
    Clemens et al. 2017, in prep.
    0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    l=1 hDAV periods, observed
    0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    l=1 canonical MH
    simulation
    Full evolutionary models computed
    by Alejandra Romero et al.
    2012, MNRAS, 420, 1462
    Only drawing from
    the models with
    canonically thick MH

    View full-size slide

  26. Asteroseismology: Insights from the Aggregated Periods
    Clemens et al. 2017, in prep.
    0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    l=1 hDAV periods, observed
    0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    l=1 canonical MH
    simulation
    Full evolutionary models computed
    by Alejandra Romero et al.
    2012, MNRAS, 420, 1462
    10-15 s offset: Suggests He-layer
    masses too thick in canonical models
    à Would lead to systematically
    younger WD cooling ages
    Only drawing from
    the models with
    canonically thick MH

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  27. Tuning the White Dwarf Clocks with Eclipses & Pulsations
    A ‘typical’ white dwarf
    electron degenerate
    C/O core
    (r = 8500 km)
    non-degenerate
    He layer
    (260 km) non-degenerate
    H layer
    (30 km)
    [thermal reservoir]
    [insulating blanket]
    - Seismology: ~80% of WDs have
    canonically thick envelopes
    - Those with thinner He layers
    can cool >10-25% more slowly
    - Seismic evidence that those with
    thick MH
    may have thinner MHe
    (are systematically older than we think)
    - K2 data still coming in: Expect many
    core C/O ratio constraints very soon!

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