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New Light on Interior Processing of Failed Core-Collapse Supernovae

jjhermes
August 11, 2014

New Light on Interior Processing of Failed Core-Collapse Supernovae

Conference presentation, 15 min. August 2014: 19th European White Dwarf Workshop, Montreal, Canada.

jjhermes

August 11, 2014
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  1. University  of  Warwick
    McDonald  Observatory


    with Boris Gänsicke, Detlev Koester, S. O. Kepler, Barbara G. Castanheira,
    A. Gianninas, D. E. Winget, M. H. Montgomery, and Warren R. Brown

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  2. photo  by  Leah  B.  Flippen

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  3. 1. Asteroseismology of
    massive (>1.1 M¤
    ) WDs

    New Light on Massive White Dwarf Interiors
    2. Detailed abundance studies of
    potential bared ONe-core WDs

    photo  by  M.S.  Sliwinski  &  L.  I.  Slivinska
    photo  by  Jørgen  Christensen-­‐‑Dalsgaard

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  4. WD Photosphere: The Top 0.000000000000001%
    Fontaine  &  Brassard  2008,  PASP,  120,  1043
    Fractional  Mass  Depth:
    Core
    Surface

    1%
    0.0001%

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  5. WD Photosphere: The Top 0.000000000000001%
    Fontaine  &  Brassard  2008,  PASP,  120,  1043
    Fractional  Mass  Depth:
    Core
    Surface

    1%
    0.0001%

    99.9999%

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  6. WD Photosphere: The Top 0.000000000000001%
    Fontaine  &  Brassard  2008,  PASP,  120,  1043
    Fractional  Mass  Depth:
    Core
    Surface

    1%
    0.0001%

    99.9999%

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  7. Winget  &  Kepler  2008,  ARA&A,  46,  157
    Fontaine  &  Brassard  2008,  PASP,  120,  1043
    Fractional  Mass  Depth:
    N2
    Ll
    2
    “Propagation  Diagram”
    Core
    Surface

    Seeing Below the Skin
    Takeaway:  Chemical  transitions  
    cause  a  “bump”  in  N2,  and  thus  a  
    detectable  asteroseismic  
    signature
    p-modes

    σ2  >  Ll
    2,  N2
    g-modes

    σ2  <  Ll
    2,  N2
    convection

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  8. BPM 37093: The 1.1 M¤
    DAV
    •  12,000  K,  >  1.1  M¤
     WDs  
    should  have  significantly  
    crystallized  cores
    •  Atsuko  NiRa  poster:  [C7]
    Discovery:  Kanaan  et  al.  1992,  ApJ,  390,  L89 photo  by  Ruth  Bazinet  /  Harvard-­‐‑CfA
    Crystallized mass fraction
    assuming pure O core

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  9. A Quick Reminder about Crystallization
    •  Crystallization  occurs  when: i
    >k
    B
    T    <<    (Ze)2    
         
     
    thermal  energy  of  ions  <<  energy  of  Coulomb  interaction  between  neighboring  ions
    •  Ions  seRle  into  laRice  structure
    •  Releases  heat;  slows  WD  cooling
    photo  by  Ruth  Bazinet  /  Harvard-­‐‑CfA
    “Lucy”  (?!)
    Mike  Montgomery

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  10. From  2.3  m  Bok  @  
    Steward  Obs.  (2009)  
    Gianninas  et  al.  2011:
     
    Teff
     =  12,030  ±  210  K
    log(g)  =  9.08  ±  0.06
    (S/N  ~  55)

    MWD
     =  1.20  ±  0.03  M¤
    GD 518: A Newly Minted 1.2 M¤
    DAV
    Hermes  et  al.  2013,  ApJ,  771,  L2
     

    From  1.5  m  @  
    Whipple  (2013)

    T
    eff
     =  12,100  ±  370  K
    log(g)  =  9.0  ±  0.09
    (S/N  ~  15)
    J16  59  15.11  +66  10  33.3  (g  =  17.2  mag)
    Gianninas  et  al.  2011,  ApJ,  743,  138

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  11. GD 518: A Newly Minted 1.2 M¤
    DAV
    NOV <0.1% using

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  12. GD 518: A Newly Minted 1.2 M¤
    DAV
    Hermes  et  al.  2013,  ApJ,  771,  L2

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  13. At  least  three  significant,  independent  modes:
    f
    1
    :  440.2  ±  1.5  s
    f
    2
    :  513.2  ±  2.4  s
    f
    3
    :  583.7  ±  1.5  s


    GD 518: A Newly Minted 1.2 M¤
    DAV
    Hermes  et  al.  2013,  ApJ,  771,  L2
    FT  of  all  42.9  hr  
    in  2013  Mar/Apr
    500 s
    250 s

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  14. Thai National 2.4 m à 4.2 m WHT on La Palma à McDonald 2.1m?
    GD  518:  J16  59  15.11  +66  10  33.3  (g  =  17.2  mag)

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  15. Thai National 2.4 m à 4.2 m WHT on La Palma à McDonald 2.1m?
    GD  518:  J16  59  15.11  +66  10  33.3  (g  =  17.2  mag)

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  16. •  Elements  become  stratified  with  
    cooling  ages  >1  Gyr
    •  LiRle  hope  of  probing  deeper  
    than  C/O  transition  layer
    Problem: Crystallization Veils Interior Composition
    Corsico  et  al.  2004,  A&A,  427,  923
    Montgomery  &  Winget  1999,  ApJ,  526,  976
    H/He

    He/C

    C/O

    O/Ne

    (1.06  M¤
     model)
    GD 518

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  17. Massive DAVs Likely Have Low Mode Inertia
    Montgomery  &  Winget  1999,  ApJ,  526,  976
    •  Kinetic  energy  of  
    pulsations  cannot  
    propagate  inside  
    crystallized  core
    •  Massive  DAVs  thus  
    likely  have  very  low  
    mode  inertia  
    (<  0.02  M¤
     participating          
    in  pulsations)
    •  Amplitude  changes  
    in  massive  DAVs:  
    evidence  of  core  
    crystallization?
    Core
    Surface

    12,200 K, 1.1 M¤
    WD model

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  18. New Light on Massive White Dwarf Interiors
    2. Detailed abundance studies of
    potential bared ONe-core WDs

    photo  by  M.S.  Sliwinski  &  L.  I.  Slivinska

    View full-size slide

  19. Towards Interior Processing in Massive WDs
    Gänsicke  et  al.  2010,  Science,  327,  188
    •  SDSS  J1102+2054  (fit  here  has  
    T
    eff
     =  10,500  K,  log(g)  ~  8.0)
    •  O/C  >  10
    •  >  500  Myr,  expect  diffusion  to  
    leave  more  C  than  O
    •  Best  explanation:  essentially  no  
    H,  He:  bared  O/Ne-­‐‑core  WDs

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  20. Towards Interior Processing in Massive WDs
    •  SDSS  J1102+2054  limits  on  
    Mg
    •  Photometric  T
    eff
     =  8150  K
    •  O  in  spectra:  T
    eff
     =  10,500  K
    •  UV  opacities?
    Model

    Synthetic

    log(Mg/H) = -9

    log(Mg/H) = -6.1

    HST, 3 orbits

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  21. Conclusions: More Insights into Massive WDs without H
    •  GD  518  is  a  new  1.2  M¤
     
    massive  DAV  with  
    significant  amplitude  
    variations
    •  Massive  DAVs  may  
    yield  more  insight  into  
    crystallization  than  
    interior  processing
    •  Massive  DBVs  would  
    not  be  crystallized
    •  Bared-­‐‑ONe-­‐‑core  WDs  a  
    unique  avenue  into  
    interior  processing  of  
    massive  WDs
    •  Stay  tuned!

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  22. Changing (Ze)2
    Montgomery  &  Winget  1999,  ApJ,  526,  976

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  23. BPM 37093: The 1.1 M¤
    DAV
    •  Whole  Earth  Telescope  campaigns:  
    rich  census  of  pulsations
    •  The  best-­‐‑fit  models  find  a  crystallized  
    mass  fraction  of  up  to  90%  (Metcalfe,  
    Montgomery  &  Kanaan  2004,  ApJ,  605,  L133),  
    ~50%  (Kanaan  et  al.  2005,  A&A,  432,  219)  or  
    32-­‐‑82%  (Brassard  &  Fontaine  2005,  ApJ,  622,  572)
    •  Nearly  as  many  free  parameters  as  the  
    10  pulsation  modes  that  have  been  
    constrained…
    Kanaan  et  al.  2005,  A&A,  432,  219
    A. Kanaan et al.: WET observations of BPM 37093 223
    Fig. 2. Fourier Transforms and window functions at the same scale for the Whole Earth Telescope observations of the ZZ Ceti star BPM 37093
    obtained during a) the XCOV 16 campaign in 1998, and b) the XCOV 17 campaign in 1999.
    hydrogen profiles that were derived assuming diffusive equilib-
    rium in the trace element approximation. This produced unre-
    alistically sharp chemical gradients at the base of the hydro-
    gen layer, leading to stronger mode trapping in their models.
    This was demonstrated by Córsico et al. (2002), who compared
    models that assumed diffusive equilibrium in the trace element
    approximation with models that computed the abundance pro-
    files based on time-dependent diffusion calculations. In a recent
    extension of this work to massive ZZ Ceti stars, Althaus et al.
    (2003) described an improved method of calculating diffusive
    equilibrium profiles that compare favorably with the fully time-
    dependent results (see their Fig. 18). We have incorporated this
    method of computing the hydrogen abundance profiles into the
    code used by Montgomery & Winget (1999). However, since
    the sharpness of the hydrogen transition zone should mainly
    affect the mode trapping properties of the models, we expect
    that our new average period spacings will differ only slightly
    from those computed by Montgomery & Winget (1999).
    As a simple illustration of the potential of our observations,
    we calculated ∆P for a small grid with various combinations
    of MH
    and Mcr
    . We fixed the mass, temperature, and helium
    layer thickness to the values used for Fig. 10b of Montgomery
    & Winget (1999), but we assumed a uniform O core. We
    show this grid of models in Fig. 3 with the shaded 1σ range
    of the average period spacing from the WET observations of
    BPM 37093. As expected, the average period spacing of the
    0% crystallized model is virtually identical to that found by
    Montgomery & Winget (1999). However, due to the different
    assumed C/O profiles, the crystallized curves have shifted with
    respect to the results of Montgomery & Winget (1999).
    Unfortunately, the degeneracy between MH
    and Mcr
    is still
    present, but we have not yet used the hidden third dimension of
    Fig. 3. The average period spacing of a small grid of models with var-
    ious combinations of MH
    and Mcr
    . The 1σ range of the observed av-
    erage period spacing for BPM 37093 is shown as a shaded area, and
    the circled point indicates the model with the smallest rms difference
    between the observed and calculated periods (see text for details).
    log(MH/M∗
    ) = −6 and Mcr = 50% has σP = 1.08 s, which
    is substantially better than anything else in this small grid (the
    next best model has σP = 1.70 s). A theoretical model with
    (Hydrogen  layer  mass)
    667 s
    555 s
    476 s

    1  mma  =  0.1%  relative  amplitude

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  24. Photometry of GD 518 Also Suggests High Mass

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