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Stellar Autopsies from White Dwarf Pulsations

jjhermes
September 05, 2018

Stellar Autopsies from White Dwarf Pulsations

Conference presentation, 25 min. September 2018: PHysics of Oscillating STars, Banyuls-sur-mer, France

jjhermes

September 05, 2018
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  1. http://jjherm.es
    J.J. Hermes
    Hubble Fellow
    University of North Carolina
    at Chapel Hill
    Stellar Autopsies from
    White Dwarf Pulsations

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  2. =160 copies!

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  3. 170,000 K have the highest number of detected modes. The first class of pulsating s
    5.5 5.0 4.5
    Planetary Nebula
    Main
    sequence
    DOV
    DBV
    DAV
    4.0 3.5 3.0
    log [T
    eff
    (K)]
    4
    2
    0
    –2
    –4
    log (L/L )
    Figure 3
    H
    He
    CO
    ¤
    White dwarfs:
    Peering 6 Gyr into
    our Sun’s future…
    See wonderful reviews by:
    Winget & Kepler 2008
    Fontaine & Brassard 2008
    Althaus, Córsico, Isern & García-Berro 2010

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  4. KIC08626021: Noemi Giammichele et al. 2018
    Core Surface
    ß 99% of mass
    X(O) = 78.03% ± 4.2%
    X(C) = 21.96% ± 4.2%
    X(He) = 0.0113% ± 0.006%
    With enough pulsation modes we can model entire white dwarf

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  5. 1000 s 200 s
    500 s 125 s
    White Dwarfs: g-modes, not all
    modes are observed excited
    BiSON; Thompson et al. 2003
    5 min 4 min
    6 min
    Solar p-modes
    My focus today:
    On observations of
    driving & dynamics
    in white dwarfs

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  6. 1000 s 200 s
    500 s 125 s
    White Dwarfs: g-modes, not all
    modes are observed excited
    l=1
    l=2

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  7. 1000 s 200 s
    500 s 125 s
    White Dwarfs: g-modes, not all
    modes are observed excited
    l=1
    l=2

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  8. External Constraints: Spectroscopy à Atmospheric Params.
    SDSS
    4.2m SOAR telescope
    WDs Evolve (Cool) à
    Blue: Observed by Kepler
    Open: Ground-based
    fits via
    Pier-Emmanuel
    Tremblay
    Note: Most white dwarfs: 0.55-0.70 M
    ¤
    (evolved from 1.0-3.0 M
    ¤
    ZAMS)

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  9. Blue: Observed by Kepler
    Open: Ground-based
    External Constraints: Spectroscopy à Atmospheric Params.

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  10. 150 s
    1000 s
    as white dwarfs
    cool:
    convection zone
    deepens and
    longer-period
    (higher-radial-order)
    pulsations driven

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  11. 150 s
    1000 s
    as white dwarfs
    cool:
    convection zone
    deepens and
    longer-period
    (higher-radial-order)
    pulsations driven

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  12. SDSS
    Hermes et al. 2017c
    500 s 200 s 118 s
    Nyquist
    ambiguity
    EPIC 211914185
    Kp
    = 18.9 mag

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  13. Hermes et al. 2017c
    500 s 200 s 118 s
    Prot
    : 1.13 0.02 hr
    Ground-based time-series photometry
    breaks Nyquist ambiguity
    EPIC 211914185
    l = 1
    n = 1
    l = 1
    n = 2
    MWD
    : 0.87 ± 0.03 M¤
    MProg.
    : 4.0 ± 0.5 M¤
    This is the fastest-rotating isolated white dwarf

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  14. 1 10 100
    WD Rotation Period (hr)
    0.4
    0.5
    0.6
    0.7
    0.8
    0.9
    WD Mass (M )
    1.0
    1.5
    2.0
    2.5
    3.0
    3.5
    4.0
    ZAMS Progenitor Mass (M )
    1 10 100
    White Dwarf Rotation Period (hr)
    0
    2
    4
    6
    8
    10
    12
    14
    N
    K2 C8-14
    Hermes+ (2017d)
    Kawaler (2015)
    1 d 2 d 4 d
    We Can Now Probe WD Rotation as a Function of Mass
    Most white dwarfs evolve from 1-3 M¤
    ZAMS stars,
    and rotate with periods of 0.5-2.2 days
    1 d 2 d 4 d
    Hermes et al. 2017d

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  15. 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
    n = 1
    l = 1
    n = 2
    l = 1
    n = 3
    Mode Period (s)
    N
    SDSSJ0051+0339, g=17.6, K2 Campaign 8
    n = 1 n = 2 n = 3 n = 4
    Chris Clemens et al. 2018, in prep.
    White Dwarfs Seismologist’s Dilemma: Often Few Modes
    Kepler makes mode identification
    relatively trivial

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  16. 0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    Mode Period (s)
    N
    l = 1
    n = 1
    l = 1
    n = 2
    l = 1
    n = 3
    n = 1 n = 2 n = 3 n = 4
    Clemens et al. 2018, in prep.
    If we only plot identified l=1 (m=0) modes:
    Kepler makes mode identification
    relatively trivial
    White Dwarfs Seismologist’s Dilemma: Often Few Modes

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  17. 0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    Mode Period (s)
    N
    n = 1 n = 2 n = 3 n = 4
    l = 1
    n = 1
    l = 1
    n = 2
    l = 1
    n = 3
    Clemens et al. 2018, in prep.
    If we only plot identified l=1 (m=0) modes:
    Kepler makes mode identification
    relatively trivial
    White Dwarfs Seismologist’s Dilemma: Often Few Modes

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  18. 0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    l=1 DAV periods, observed
    Full evolutionary models computed
    by Romero et al. 2012
    Clemens et al. 2018, in prep.
    White Dwarfs Seismologist’s Dilemma: Often Few Modes

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  19. Drawing from a random distribution of
    all hydrogen layer masses
    Full evolutionary models computed
    by Romero et al. 2012
    0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    l=1 DAV 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
    Clemens et al. 2018, in prep.
    White Dwarfs Seismologist’s Dilemma: Often Few Modes

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  20. 0
    1
    2
    3
    4
    5
    6
    7
    8
    50 100 150 200 250 300 350 400 450
    l=1 DAV 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 Romero et al. 2012
    Only drawing from the
    models with canonically thick
    (10-4 MH
    /M
    ) hydrogen layers
    Clemens et al. 2018, in prep.
    Most (>80% of) DAVs Have Thick H Layers

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  21. 150 s
    1000 s
    as white dwarfs
    cool:
    convection zone
    deepens and
    longer-period
    (higher-radial-order)
    pulsations driven

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  22. Kepler Has Revealed a Dichotomy of Mode Linewidths
    Two modes within the same
    DAV show very different
    linewidths
    (Absolutely no way to have
    made these measurements
    before Kepler)

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  23. Kepler Has Revealed a Dichotomy of Mode Linewidths
    Results from fitting Lorentzians to
    power spectra of 27 DA white dwarfs:
    Clear dichotomy at ~800 s
    Hermes et al. 2017d

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  24. ’Mottled’ Modes: Outside of Mode Cavity is Base of CZ
    Damping rather than driving
    important for broadening; phase incoherence
    ‘Mottled’ modes: bounded by the
    base of the convection zone!
    Mike Montgomery et al. 2018, in prep.

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  25. Used to Be, Getting Data Required
    Going to the Telescope

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  26. *PG 1159 star = hot pre-white-dwarf (aka DOV)

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  27. Vauclair et al. 2002
    Maidanak Observatory,
    Uzbekistan
    2-week coordinated, global (14-site)
    Whole Earth Telescope run in 1994

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  28. THE MAIN LOG
    Observations at Maidanak observatory in Uzbekistan. Aug 1994
    Observers: E. Meistas, and local assistant Alexey V. Chernyshev

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  29. Jul 27th
    Uzbeks introduced new rules for the visas ... spent long
    8 night hours in the old stinking Russian bus, which,
    using longest possible route and stopping more than ten
    times for the repairs, after which passengers were
    supposed to push the bus to start the engine, brought us
    to Shakhrisabz.
    Jul 28th
    Old military jeep, which exhaust went more inside
    than via its pipes, after 5 hours brought us to
    Maidanak [Observatory]. ... Some windows of our
    living house were broken, no clean sheets ... no
    butter, meat, sugar. Running water system was not
    working anymore, not to mention hot water.
    THE MAIN LOG
    Observations at Maidanak observatory in Uzbekistan. Aug 1994
    Observers: E. Meistas, and local assistant Alexey V. Chernyshev

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  30. Jul 29th
    I checked telescope; tracking and positioning were
    working, but telescope mirrors needed cleaning...
    Jul 30th
    Managed to repair distiller and to get 3 L of water late
    in the evening. Decided to wash mirrors next day. Still
    lots of yellow Afghanistan dust in the sky.
    Jul 31st
    Washed mirrors, cleaned telescope inner surfaces from
    thick dust layer. Started the full scale system test.
    THE MAIN LOG
    Observations at Maidanak observatory in Uzbekistan. Aug 1994
    Observers: E. Meistas, and local assistant Alexey V. Chernyshev

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  31. Aug 1st
    All day no clouds, but wind increasing to the
    evening. Worked all night.
    Aug 3rd
    All day clear sky with some clouds. Quite strong wind in
    day time but diminished before the night.
    THE MAIN LOG
    Observations at Maidanak observatory in Uzbekistan. Aug 1994
    Observers: E. Meistas, and local assistant Alexey V. Chernyshev

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  32. Aug 5th
    It was first night there on the mountain without me. I was
    at that time in Kitab Hospital severely injured by the
    Tashkent Astrophysical Institute Director son Iskander
    Yuldashbaev, apparently mentally ill young man of about 21.
    THE MAIN LOG
    Observations at Maidanak observatory in Uzbekistan. Aug 1994
    Observers: E. Meistas, and local assistant Alexey V. Chernyshev

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  33. Aug 5th
    It was first night there on the mountain without me. I was
    at that time in Kitab Hospital severely injured by the
    Tashkent Astrophysical Institute Director son Iskander
    Yuldashbaev, apparently mentally ill young man of about 21.
    He did some cleaning ... suddenly saying no words grabbed my
    hair with his left hand and hit my throat with a broken
    knife from our kitchen. I ran in horror, but he managed to
    hit me twice into my back. I ran to the Russian house for
    the help all in the blood. It was no phone connection with
    outside world and two of them had to run all the way to
    Maidanak to soldiers, and in three hours at last I was
    delivered to Kitab hospital in rather weak condition.
    THE MAIN LOG
    Observations at Maidanak observatory in Uzbekistan. Aug 1994
    Observers: E. Meistas, and local assistant Alexey V. Chernyshev

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  34. THE MAIN LOG
    Observations at Maidanak observatory in Uzbekistan. Aug 1994
    Observers: E. Meistas, and local assistant Alexey V. Chernyshev
    Aug 5th
    It was first night there on the mountain without me. I was
    at that time in Kitab Hospital severely injured by the
    Tashkent Astrophysical Institute Director son Iskander
    Yuldashbaev, apparently mentally ill young man of about 21.
    He did some cleaning ... suddenly saying no words grabbed my
    hair with his left hand and hit my throat with a broken
    knife from our kitchen. I ran in horror, but he managed to
    hit me twice into my back. I ran to the Russian house for
    the help all in the blood. It was no phone connection with
    outside world and two of them had to run all the way to
    Maidanak to soldiers, and in three hours at last I was
    delivered to Kitab hospital in rather weak condition.
    ... He is in a custody now and cannot say the reason either,
    says he did not like the way I looked at him. But he was
    smart enough to steal before that event good sum of my money
    ... Until helicopter arrived I explained the basics of the
    work with the quilt program to Alexey -- my assistant.
    Luckily I trained him on almost everything...

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  35. Aug 10th
    Alexey arrived from the Maidanak in the afternoon.
    Everything seems OK.
    Aug 11th Aug 12th
    I lived in the Russian hotel in Kitab ... working with
    data: writing logs, marking bad points. Tomorrow night
    Uzbeks promised to bring me to the Samarkand airport.
    My throat is swollen, still hurts and ugly.
    END OF CAMPAIGN HERE IN THE UZBEKISTAN
    ------------------------------------------------------------------------
    THE MAIN LOG
    Observations at Maidanak observatory in Uzbekistan. Aug 1994
    Observers: E. Meistas, and local assistant Alexey V. Chernyshev
    Aug 8th
    I ... practically defected from Kitab hospital, where
    black bugs were running on the walls at night even in
    the patient's beds, over the face too. Throat is badly
    swollen and hurts.

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  36. Today We Are Spoiled with
    Telescopes in Space

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  37. 150 s
    1000 s
    as white dwarfs
    cool:
    convection zone
    deepens and
    longer-period
    (higher-radial-order)
    pulsations driven
    and
    mode density
    rapidly increases

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  38. A Visual Guide to Outbursts in Pulsating White Dwarfs
    Quiescent pulsations
    (All outburstersdominant >800 s)
    PG 1149+057: Hermes et al. 2015b
    see also Bell et al. 2015, 2016
    recurrence time:
    chaotic; days to weeks
    duration:
    2-20 hr
    excess energy:
    1033-34 erg
    15% flux increase:
    700 K Teff
    increase

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  39. Outbursting DAVs are Among the Coolest DAVs
    Blue: Observed by Kepler
    Red: Outbursting DAV
    Open: Ground-based
    more than 50% of DAVs from 11,200-10,600 K
    show outbursts in ~70 days of K2 monitoring
    16/71 (>20% of) DAVs with Kepler data show outbursts

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  40. GD 1212: The Brightest Outbursting White Dwarf
    Quiescent pulsations
    (1135.2 s, 856.9 s, …)
    In Outburst
    (864.1 s, 846.4 s, …)
    GD 1212: Hermes et al. 2018, in prep.
    >60 days between outbursts!
    K2 Campaign 12

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  41. K2 Campaign 12

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  42. 150 s
    1000 s
    as white dwarfs
    cool:
    convection zone
    deepens and
    longer-period
    (higher-radial-order)
    pulsations driven
    and
    mode density
    rapidly increases

    View full-size slide

  43. l=1
    l=2
    Adiabatic Model: 11,245 K, 0.632 M¤
    , 10-4.12 MH
    /MWD
    Observed: 11,060(170) K, 0.64(0.03) M¤
    (Romero et al. 2012)
    (Gianninas et al. 2011)
    Outbursts: Mode Coupling via Parametric Resonance
    à Driving exceeds damping
    Radiative damping ß
    outbursts are likely “limit cycles arising from sufficiently
    resonant 3-mode couplings between overstable parent
    modes and pairs of radiatively damped daughter modes”
    Luan & Goldreich 2018

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  44. à Driving
    Radiative damping ß
    l=1
    l=2
    Adiabatic Model: 11,245 K, 0.632 M¤
    , 10-4.12 MH
    /MWD
    Observed: 11,060(170) K, 0.64(0.03) M¤
    (Romero et al. 2012)
    (Gianninas et al. 2011)
    ωp
    = 897.7 µHz
    (l=1, m=0, n=24)
    Outbursts: Mode Coupling via Parametric Resonance

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  45. ωp
    = 897.7 µHz
    (l=1, m=0, n=24)
    ωd1
    = 435.9 µHz
    (l=2, m=0, n=88)
    l=1
    l=2
    ωd2
    = 461.9 µHz
    (l=1, m=0, n=48)
    Adiabatic Model: 11,245 K, 0.632 M¤
    , 10-4.12 MH
    /MWD
    Observed: 11,060(170) K, 0.64(0.03) M¤
    (Romero et al. 2012)
    (Gianninas et al. 2011)
    Wu & Goldreich 2001
    ωd1
    + ωd2
    = ωp
    + δω
    Limit cycle if: δω < γd
    (typical 1/γd
    < 1 day)
    Outbursts: Mode Coupling via Parametric Resonance

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  46. 150 s
    1000 s
    as white dwarfs
    cool:
    convection zone
    deepens and
    longer-period
    (higher-radial-order)
    pulsations driven
    and
    mode density
    rapidly increases

    View full-size slide