New Light on Interior Processing of Failed Core-Collapse Supernovae

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

Transcript

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
2. photo  by  Leah  B.  Flippen
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
4. WD Photosphere: The Top 0.000000000000001% Fontaine  &  Brassard  2008,  PASP,  120,  1043 Fractional  Mass  Depth: Core Surface 1% 0.0001%
5. WD Photosphere: The Top 0.000000000000001% Fontaine  &  Brassard  2008,  PASP,  120,  1043 Fractional  Mass  Depth: Core Surface 1% 0.0001% 99.9999%
6. WD Photosphere: The Top 0.000000000000001% Fontaine  &  Brassard  2008,  PASP,  120,  1043 Fractional  Mass  Depth: Core Surface 1% 0.0001% 99.9999%
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
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
9. A Quick Reminder about Crystallization •  Crystallization  occurs  when: <r 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
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
11. GD 518: A Newly Minted 1.2 M¤ DAV NOV <0.1% using
12. GD 518: A Newly Minted 1.2 M¤ DAV Hermes  et  al.  2013,  ApJ,  771,  L2
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
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)
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)
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
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
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
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
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
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!
23. Changing (Ze)2 Montgomery  &  Winget  1999,  ApJ,  526,  976
24. 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
25. Photometry of GD 518 Also Suggests High Mass