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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
IntroductionZZ Ceti starsKUV 08368+4026
New observationsPreliminary results of asteroseismologyDiscussion on variations of FTFuture Plans
Introduction of ZZ Ceti Stars
ZZ Ceti stars (DAV white dwarfs):
- the lowest Teff among the 4 classes of variable white dwarfs (DAV, DBV, DQV, GW Vir)
The DAVs (ZZ Ceti)148 members (Castanheira et al. 2010)Periods: 100 – 1500 sInternal stucture:
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)
The FTs of 4 ZZ Ceti stars
(G29-38, HL Tau 76, G255-2, KUV08368+4026)
show similar character,large amplitudescommon frequencies (1.6 mHz and 2.0 mHz) the similarity is probably the signature of some
fundamental mechanism.
Journal of new observations in BDate Observatory Telescope Frames Nights
Feb.10-18.2009
Lijiang 2.40 m 6805 8
Dec.12-18.2009
Xinglong 2.16 m 1651 6
Dec.26-31.2009
Lijiang 2.40 m 2328 3
Dec.27-28.2009
Xinglong 2.16 m 815 1
Jan.07-17.2010
SPM 1.50 m 2771 7
Jan.12-19.2010
Xinglong 2.16 m 2745 6
Frequency List
---------------------------------------------------
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
----------------------------------------------------
-------------------------------------------------
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
-------------------------------------------------
Preliminary results of asteroseismology
19 periods extracted8 eigenmodes foundedmode identification: l=1, 2triplets: average δf=1.12 µHz
→rotational period: P=3.09 dayaverage ΔP=32.6 s for l=1
→ M=0.6-0.7 M ⊙
The 1.6mHz frequency found in 1996 disappeared.
Amplitude variation
Time scale of variation: weeksExplanation:
Not a evolutionary effectInteraction of rotation and pulsation?Interaction of convection and pulsation?
Calculation of Total Power
Runs Σ(An)2 (mma2)
2009.2 1044.1
2009.12.1 778.5
2009.12.2 1146.4
2010.1 933.5
Future plans
To get high-precision stellar parameters (High-Resolution Spectroscopic data needed)
Call a WET Campaign for
KUV 08368+4026Theoretical study with the white dwarf
Modelling Code (Toulouse)