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Rolling in their Graves: White Dwarf Rotation as a Function of Mass

jjhermes
July 23, 2018

Rolling in their Graves: White Dwarf Rotation as a Function of Mass

Conference presentation, 13 min. July 2018: 21st European Workshop on White Dwarfs, Austin, TX, USA.

jjhermes

July 23, 2018
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  1. J.J. Hermes
    Hubble Fellow
    University of North Carolina
    at Chapel Hill
    Rolling in their Graves: White Dwarf
    Rotation as a Function of Mass
    Boris Gänsicke, Steve Kawaler, Sandra Greiss, Pier-
    Emmanuel Tremblay, Nicola Pietro Gentile Fusillo,
    Roberto Raddi, Stephen Fanale, Keaton Bell, Erik
    Dennihy, Josh Fuchs, Joshua Reding, Ben Kaiser, Bart
    Dunlap, Chris Clemens, Mike Montgomery, Don
    Winget, Paul Chote, Tom Marsh, and Seth Redfield
    Isolated,
    canonical-mass
    white dwarfs
    rotate between
    0.5-2.0 days

    View Slide

  2. Tremblay et al. 2011
    Karl et al. 2005
    SDSS
    Keck/HIRES
    solid:
    v sin i = 11 km/s
    dashed:
    v sin i = 0 km/s
    White dwarfs
    typically have
    unmeasurable
    v sin i (<15 km/s)
    (Prot
    > hours)
    Broad Balmer lines
    NLTE Hα core

    View Slide

  3. m = +1
    m = -1
    m = 0
    1000 s 200 s
    500 s 125 s
    316.8 s
    345.3 s
    n = Number of radial nodes
    l = Number of vertical nodes
    m = Number of horizontal + vertical nodes
    n
    l = 1
    n = 5
    l = 1
    n = 6
    Prot
    = 0.9
    ± 0.2 day
    Asteroseismology gives us
    our clearest insight into
    white dwarf rotation
    Data from a typical pulsating
    white dwarf observed by Kepler
    (g = 18.2 mag)

    View Slide

  4. Original Kepler Mission (4 years):
    Just 20 white dwarfs observed,
    6 pulsating WDs (just two >3 months)
    K2 through Campaign 16:
    >2100 white dwarfs observed
    71 more pulsating WDs
    K2 has given us hundreds of
    candidate pulsating white
    dwarfs to observe

    View Slide

  5. Model-Independent Rotation Falls Readily from K2 Data
    Hermes et al. 2017d
    k2wd.org
    Assume Ck,l
    =0.47 in all
    cases for modes
    l=1

    View Slide

  6. 1 10 100
    White Dwarf Rotation Period (hr)
    0
    2
    4
    6
    8
    10
    N
    Kepler & K2
    Kawaler (2015)
    Most isolated white
    dwarfs rotate between
    0.5-2.2 days
    None of the stars are
    currently in binaries:
    Representative of
    single-star evolution
    of mostly 1-3 M¤
    stars
    Model-Independent Rotation Falls Readily from K2 Data
    0.5 d 1 d 2 d 4 d
    Hermes et al. 2017d: k2wd.org

    View Slide

  7. SDSS
    SOAR spectroscopy
    yields
    WD mass
    We have
    obtained SOAR
    spectra of 62/65
    DAVs observed so
    far by Kepler/K2
    Hermes et al. 2017d: k2wd.org

    View Slide

  8. The DAV Instability Strip Observed by K2, To Date
    Blue: Observed by Kepler
    Open: Ground-based
    first 27 from Hermes et al. 2017d: k2wd.org
    3D-corrected fits carried out by
    Pier-Emmanuel Tremblay

    View Slide

  9. 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
    The fastest-rotating pulsating white dwarf (1.13 hr) is also the most
    massive (0.87 M¤
    ) – descended from a single 4.0 M¤
    ZAMS progenitor
    (Hermes et al. 2017c)
    Hermes et al. 2017d: k2wd.org

    View Slide

  10. Most white dwarfs evolve
    from 1-3 M¤
    ZAMS stars, and
    rotate at 0.5-2.2 days
    Possible link emerging between
    higher white dwarf mass and
    faster rotation
    1 10 100
    0
    1
    2
    3
    4
    5
    6
    7
    N
    0.52 0.56 M
    WD Prot = 1.48 ± 0.99 d
    1 10 100
    0
    1
    2
    3
    4
    5
    6
    7
    N
    0.57 0.64 M
    WD Prot = 1.29 ± 0.69 d
    1 10 100
    0
    1
    2
    3
    4
    5
    6
    7
    N
    0.65 0.71 M
    WD Prot = 1.33 ± 1.03 d
    1 10 100
    White Dwarf Rotation Period (hr)
    0
    1
    2
    3
    4
    5
    6
    7
    N
    0.78 0.88 M
    WD Prot = 0.17 ± 0.15 d
    We Can Now Probe WD Rotation as a Function of Mass
    Hermes et al. 2017d: k2wd.org
    (1.0-2.0 M
    ¤
    ZAMS)
    (2.0-2.5 M
    ¤
    ZAMS)
    (2.5-3.0 M
    ¤
    ZAMS)
    (3.5-4.0 M
    ¤
    ZAMS)

    View Slide

  11. in Figure 3. The pulsating pre-white dwarf PG 1159 stars, the DOVs, around 75,000 K to
    170,000 K have the highest number of detected modes. The first class of pulsating stars to be
    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
    A 13-Gyr isochrone with z = 0.019 from Marigo et al. (2007), on which we have drawn the observed
    locations of the instability strips, following the nonadiabatic calculations of C´
    orsico, Althaus & Miller
    Bertolami (2006) for the DOVs, the pure He fits to the observations of Beauchamp et al. (1999) for the
    DBVs, and the observations of Gianninas, Bergeron & Fontaine (2006) and Castanheira et al. (2007, and
    references therein) for the DAVs.
    172 Winget ·Kepler
    2.5 M¤
    A star:
    Prot,ZAMS
    ~ 10 hr
    Core-He RGB: modes
    ~0.02-0.10 R¤
    Prot
    : 30-180 d
    White dwarf: ~0.005-0.013 R¤
    Prot
    : 0.5-2.2 d
    10 100
    Secondary Clump Rotation Period (d)
    0
    1
    2
    3
    4
    5
    6
    7
    8
    N
    Deheuvels et al. 2015
    Tayar et al., in prep.
    Kepler has
    mapped internal
    rotation evolution
    all the way from
    MS to WD
    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)

    View Slide

  12. Where are We Going with White Dwarf Rotation?
    Coming Soon: NASA TESS will
    observe all bright WDs every
    2 min for ~27 d
    815 white dwarfs brighter than I < 16 mag
    accepted in Cycle 1 target list (Ecliptic South):
    dozens of new pulsators and rotation rates
    Exploring v sin i of UVES spectra
    of massive (>0.8 M¤
    ) DAs with
    T
    eff
    > 15,000 K (ESO 0101.D-0295)

    View Slide

  13. k2wd.org

    View Slide

  14. 1 10 100
    0
    1
    2
    3
    4
    5
    6
    7
    N
    0.52 0.56 M
    WD Prot = 1.48 ± 0.99 d
    1 10 100
    0
    1
    2
    3
    4
    5
    6
    7
    N
    0.57 0.64 M
    WD Prot = 1.29 ± 0.69 d
    1 10 100
    0
    1
    2
    3
    4
    5
    6
    7
    N
    0.65 0.71 M
    WD Prot = 1.33 ± 1.03 d
    1 10 100
    White Dwarf Rotation Period (hr)
    0
    1
    2
    3
    4
    5
    6
    7
    N
    0.78 0.88 M
    WD Prot = 0.17 ± 0.15 d
    White Dwarf Rotation as Function of Mass Revealed by K2
    k2wd.org
    1-3 M¤
    on ZAMS evolve into
    WDs rotating at 0.5-2.2 d
    (35 hr w/ std. dev. 28 hr)
    - Kepler suggests that most core angular
    momentum lost on first ascent up RGB
    Evidence is emerging that more
    massive WDs rotate faster
    - More massive ZAMS stars rotate faster
    - More massive ZAMS spend less time on
    first-ascent RGB
    (1.0-2.0 M
    ¤
    ZAMS)
    (2.0-2.5 M
    ¤
    ZAMS)
    (2.5-3.0 M
    ¤
    ZAMS)
    (3.5-4.0 M
    ¤
    ZAMS)

    View Slide