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Asteroseismology of the ZZ Ceti star KUV 08368+4026

Asteroseismology of the ZZ Ceti star KUV 08368+4026. Chun LI (Beijing Normal University, China). Collaborators : J.N. Fu, G. Vauclair, L. Fox Machado, M. Alvarez, J. Su, R. Michel, X.H. Yang, Y. Li, Y.P. Zhang, N. Dolez. Aug.16-20, 2010 Tübingen. Overview. Introduction ZZ Ceti stars

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Asteroseismology of the ZZ Ceti star KUV 08368+4026

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  1. Asteroseismology of the ZZ Ceti star KUV 08368+4026 Chun LI (Beijing Normal University, China) Collaborators: J.N. Fu, G. Vauclair, L. Fox Machado, M. Alvarez, J. Su, R. Michel, X.H. Yang, Y. Li, Y.P. Zhang, N. Dolez Aug.16-20, 2010 Tübingen

  2. Overview • Introduction • ZZ Ceti stars • KUV 08368+4026 • New observations • Preliminary results of asteroseismology • Discussion on variations of FT • Future Plans

  3. Introduction of ZZ Ceti Stars ZZ Cetistars (DAV white dwarfs): －the lowest Teff among the 4 classes of variable white dwarfs (DAV, DBV, DQV, GW Vir)

  4. Pure instability strip (Li & Fu, 2010, in preparation)

  5. The DAVs (ZZ Ceti) 148 members (Castanheira et al. 2010) Periods: 100 – 1500 s Internal stucture: C/O core, He layer, H envelope Instability: κ-mechanism Teff: ~12500 K  ~11000 K; Pulsation modes: g modes

  6. Discovered in Feb.1996 With the 1.9m telescope at Haute Provence Observatory V=15.55 mag B-V=0.22 U-B=-0.59 (Vauclair et. al. 1997) ZZ Ceti Star KUV 08368+4026

  7. The FTs of 4 ZZ Ceti stars (G29-38, HL Tau 76, G255-2, KUV08368+4026) show similar character, • large amplitudes • common frequencies (1.6 mHz and 2.0 mHz) • the similarity is probably the signature of some fundamental mechanism.

  8. Location of the 4 ZZ Ceti stars on the Instability Strip HL Tau 76 KUV08368+4026 G255-2 G29-38

  9. Journal of new observations in B

  10. 2.4m Telescope of Lijiang 2.16m Telescope of Xinglong

  11. Light Curve (Feb 2009)

  12. Power spectrum (Feb 2009)

  13. Period analysis： Period04 (Lenz & Breger 2005)

  14. Frequency List ------------------------------------------------- Freq(μHz) Err Amp(mma) S/N -------------------------------------------------- 3247.77 0.03 5.3 15.49 3249.11 0.06 2.7 7.97 3885.53 0.02 11.1 17.11 3886.74 0.04 4.7 7.38 3887.73 0.01 16.7 26.04 5223.79 0.07 2.3 7.09 5747.68 0.06 2.9 9.19 6386.52 0.07 2.6 8.70 7134.37 0.04 4.6 16.13 ------------------------------------------------- --------------------------------------------------- Freq(μHz) Err Amp(mma) S/N --------------------------------------------------- 1386.90 0.04 3.9 15.04 1454.67 0.05 3.6 10.06 1976.48 0.02 10.8 20.88 2159.09 0.06 2.9 9.38 2498.75 0.02 10.5 24.90 2500.71 0.02 8.7 20.78 2757.87 0.07 2.3 5.63 2759.98 0.05 3.6 8.82 3245.51 0.06 2.9 8.76 3246.74 0.01 13.0 38.44 ----------------------------------------------------

  15. Preliminary results of asteroseismology • 19 periods extracted • 8 eigenmodes founded • mode identification: l=1, 2 • triplets: average δf=1.12 µHz →rotationalperiod: P=3.09 day • average ΔP=32.6 s for l=1 → M=0.6-0.7 M⊙ The 1.6mHz frequency found in 1996 disappeared.

  16. Light Curves (Dec 2009 part 1)

  17. Power Spectrum (Dec 2009 part 1)

  18. Light Curve (Dec 2009 Part 2)

  19. Power Spectrum (Dec 2009 Part 2)

  20. Light Curve (Jan 2010)

  21. Power Spectrum (Jan 2010)

  22. Power spectrum (Feb 2009) Discussion on variations of FT

  23. Power Spectrum (Dec 2009 part 1)

  24. Power Spectrum (Dec 2009 Part 2)

  25. Power Spectrum (Jan 2010)

  26. Amplitude variation • Time scale of variation: weeks • Explanation: • Not a evolutionary effect • Interaction of rotation and pulsation? • Interaction of convection and pulsation?

  27. Calculation of Total Power

  28. Amplitude variation also be found in HS 0507+0434B (See the Poster of Fu et al.)

  29. Power Spectrum (Dec 2009 + Jan 2010)

  30. Periods were resolved. • However, it is very difficult to do the mode identification

  31. Future plans To get high-precision stellar parameters (High-Resolution Spectroscopic data needed) Call a WET Campaign for KUV 08368+4026 Theoretical study with the white dwarf Modelling Code (Toulouse)

  32. Vielen Dank!

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