Observations of the ZZ Ceti star KUV 08368+4026

Chun Li

Beijing Normal University

Overview

Introduction of ZZ Ceti starsNew observations for KUV 08368+4026Data ReductionPreliminary ResultsFuture Work

Introduction of ZZ Ceti Stars

ZZ Ceti stars (DAV white dwarfs):

－ have the lowest Teff 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.

Pure instability strip

Stucture of White Dwarfs

The DAVs (ZZ Ceti)More than 140 membersPeriods: 100 s – 1500 sStucture:

C/O core, He layer, H envelope

Instability: κ-mechanism

Teff: ~12500 K ~11000 K;

Pulsation modes: g modes

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

Journal of new observations in BDate Observatory Telescope Flames

Feb.10-18.2009 Lijiang 2.40m 6805

Dec.12-18.2009 Xinglong 2.16m 1651

Dec.26-31.2009 Lijiang 2.40m 2328

Dec.27-28.2009 Xinglong 2.16m 815

Jan.07-17.2010 SPM 1.50m 2771

Jan.12-19.2010 Xinglong 2.16m 2745

2.4m Telescope of Lijiang

2.16m Telescope of Xinglong

1.5m Telescope of SPM

Feb 2009 Light Curve

Power spectrum(Feb 2009)

Data analysis：Period04

List of Frequencies

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Freq Err Ampl Err S/N

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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

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Freq Err Ampl Err S/N

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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

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Result:1 ） 19 periods were founded2 ） 8 independent modes3 ） Periods identification: l=1, 24 ） Triple Periods: average δf=1.12 µHz →rotational Period: P=3.09 day5 ） Average ΔP=32.6 s for l=1 → M=0.6-0.7 M ⊙

Light Curve(Dec 2009 part 1)

Light curve(Dec 2009 Part 2)

Light Curve(Jan 2010)

Future work

To finish data reductionPeriod analysisTo get stellar parametersTheoretical study with the white dwarf

Modelling Code (France)

Thanks!