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.

Transcript

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
   

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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
   

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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)
   

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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
   

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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
   

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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
   

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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
   

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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
   

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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
   

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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)
    

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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)
    

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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)
    

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13. k2wd.org
    

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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)
    

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