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Hot DQ White Dwarf Stars : A New Challenge to Stellar Evolution

Hot DQ White Dwarf Stars : A New Challenge to Stellar Evolution. Patrick Dufour,University of Arizona James Liebert, University of Arizona Gilles Fontaine, Université de Montréal Natalie Behara, Observatoire Paris-Meudon. Outline. -A Brief Introduction to White Dwarfs -Spectral Evolution

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Hot DQ White Dwarf Stars : A New Challenge to Stellar Evolution

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  1. Hot DQ White Dwarf Stars : A New Challenge to Stellar Evolution Patrick Dufour,University of Arizona James Liebert, University of Arizona Gilles Fontaine, Université de Montréal Natalie Behara, Observatoire Paris-Meudon

  2. Outline -A Brief Introduction to White Dwarfs -Spectral Evolution -DQ White Dwarfs -Hot DQ -H1504+65 and Evolutionary Scenario

  3. Jordan & Rauch 1994

  4. “Born-Again scenario” Werner & Herwig 2006

  5. RCrB? EHe? CE? ??? Evolution Hydrogen-rich Helium-rich Teff~150,000 K DA DB DC DB gap ? ? PG1159 DO DZ DC DQ ~4000 K

  6. Outline -A Brief Introduction to White Dwarfs -Spectral Evolution -DQ White Dwarfs -Hot DQ -H1504+65 and Evolutionary Scenario

  7. Dufour et al. 2005

  8. log q(He)=-4.0 log q(He)=-3.0 log q(He)=-2.0 Dufour et al. 2005 Fn=4p(R2/D2)Hn Log q(He) = MHe/M*

  9. Brassard et al. 2006

  10. Thejll et al. 1990 Wegner & Koester 1985 G 227-5 12,000 K < Teff < 13,000 K log g fixed at 8.0 C/He ~ 3x10-3 G 35-26 11,000 K < Teff < 14,000 K 8.8 < log g < 9.0 C/He ~ 3x10-2

  11. G 227-5

  12. Outline -A Brief Introduction to White Dwarfs -Spectral Evolution -DQ White Dwarfs -Hot DQ -H1504+65 and Evolutionary Scenario

  13. G 227-5

  14. Dufour et al 2005

  15. Naive expectation 1- Calculate hotter DQ models 2- Make fits 3- Write paper 4- Move on to the next project

  16. Pure Helium Log C/He = 0 Log C/He= 1 Pure Carbon

  17. 24,000 K, log g = 8.0, 8.5 and 9.0

  18. ∫Hndn = s Teff4 /4p

  19. Outline -A Brief Introduction to White Dwarfs -Spectral Evolution -DQ White Dwarfs -Hot DQ -H1504+65 and Evolutionary Scenario

  20. Werner & Herwig 2006

  21. Typical PG 1159 abundances: 33% He 50% C 15% O 2% Ne

  22. H1504+65 • Teff ~ 175,000 K – 200,000 K • Log g = 8 • C ~ 48 % • O ~ 48 % • He < 1 % • Extreme PG1159 ? • Burned carbon ? • O/Ne/Mg core ?

  23. Pure carbon, Teff = 30,000 K

  24. Evolution Helium-rich H and He poor Hydrogen-rich H1504+65 PG1159 DA 150,000 K DO ? DB Hot DQ DQ DZ DC DC ~4000 K DQ (2nd sequence ?)

  25. Conclusions -Discovery of a new type of star : white dwarfs with pure carbon atmospheres -cool down version of H1504+65? -High mass stars on MS around 8-10 Msun? -O/Ne/Mg core ? -Higher S/N observations (MMT) coming soon -more theoretical calculations/other evolutionary scenario?

  26. Thank you

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