1. Observations of the ZZ Ceti star KUV 08368+4026 Chun Li Beijing Normal University

2. Overview Introduction of ZZ Ceti stars New observations for KUV 08368+4026 Data Reduction Preliminary Results Future Work

3. Introduction of ZZ Ceti Stars ZZ Ceti stars (DAV white dwarfs): － have the lowest T eff among the four classes of variable white dwarfs (DAV, DBV, DOV, PNNV) － at the cross of the extension of the Cepheid instability strip and the evolution tracks of white dwarfs.

4. Pure instability strip

5. Stucture of White Dwarfs

6. The DAVs (ZZ Ceti) More than 140 members Periods: 100 s – 1500 s Stucture: C/O core, He layer, H envelope Instability: κ-mechanism T eff : ~12500 K  ~11000 K; Pulsation modes: g modes

7. ZZ Ceti Star KUV 08368+4026 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 )

9. Journal of new observations in B DateObservatoryTelescopeFlames Feb.10-18.2009Lijiang2.40m6805 Dec.12-18.2009Xinglong2.16m1651 Dec.26-31.2009Lijiang2.40m2328 Dec.27-28.2009Xinglong2.16m815 Jan.07-17.2010SPM1.50m2771 Jan.12-19.2010Xinglong2.16m2745

10. 2.4m Telescope of Lijiang

11. 2.16m Telescope of Xinglong

12. 1.5m Telescope of SPM

13. Feb 2009 Light Curve

14. Power spectrum(Feb 2009)

15. Data analysis ： Period04

16. List of Frequencies ------------------------------------------- Freq Err Ampl Err S/N ------------------------------------------- 1386.9042 0.0430 3.944 0.218 15.04 1454.6732 0.0464 3.653 0.218 10.06 1976.4851 0.0157 10.828 0.218 20.88 2159.0911 0.0566 2.995 0.218 9.38 2498.7566 0.0160 10.596 0.218 24.90 2500.7136 0.0194 8.757 0.218 20.78 2757.8711 0.0736 2.304 0.218 5.63 2759.9866 0.0467 3.633 0.218 8.82 3245.5122 0.0571 2.970 0.218 8.76 3246.7395 0.0130 13.052 0.218 38.44 ------------------------------------------- Freq Err Ampl Err S/N ------------------------------------------- 3247.7690 0.0321 5.283 0.218 15.49 3249.1089 0.0623 2.722 0.218 7.97 3885.5344 0.0154 11.008 0.218 17.11 3886.7449 0.0359 4.729 0.218 7.38 3887.7290 0.0101 16.751 0.218 26.04 5223.7930 0.0718 2.363 0.218 7.09 5747.6812 0.0570 2.974 0.218 9.19 6386.5161 0.0651 2.606 0.218 8.70 7134.3735 0.0364 4.659 0.218 16.13 ------------------------------------------

17. Result: 1 ） 19 periods were founded 2 ） 8 independent modes 3 ） Periods identification: l =1, 2 4 ） Triple Periods: average δf=1.12 µHz → rotational Period: P=3.09 day 5 ） Average ΔP=32.6 s for l =1 → M=0.6-0.7 M ⊙

18. Light Curve(Dec 2009 part 1)

19. Light curve(Dec 2009 Part 2)

20. Light Curve(Jan 2010)

21. Future work To finish data reduction Period analysis To get stellar parameters Theoretical study with the white dwarf Modelling Code (France)

22. Thanks!