asteroseismology of the zz ceti star kuv 08368+4026
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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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
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Overview
IntroductionZZ Ceti starsKUV 08368+4026
New observationsPreliminary results of asteroseismologyDiscussion on variations of FTFuture Plans
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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)
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Pure instability strip
(Li & Fu, 2010, in preparation)
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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
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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)
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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.
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KUV08368+4026
G29-38
HL Tau 76
G255-2
Location of the 4 ZZ Ceti stars on the Instability Strip
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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
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2.4m Telescope of Lijiang 2.16m Telescope of Xinglong
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Light Curve (Feb 2009)
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Power spectrum (Feb 2009)
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Period analysis:Period04
(Lenz & Breger 2005)
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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
-------------------------------------------------
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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.
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Light Curves (Dec 2009 part 1)
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Power Spectrum (Dec 2009 part 1)
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Light Curve (Dec 2009 Part 2)
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Power Spectrum (Dec 2009 Part 2)
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Light Curve (Jan 2010)
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Power Spectrum (Jan 2010)
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Power spectrum (Feb 2009)
Discussion on variations of FT
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Power Spectrum (Dec 2009 part 1)
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Power Spectrum (Dec 2009 Part 2)
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Power Spectrum (Jan 2010)
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Amplitude variation
Time scale of variation: weeksExplanation:
Not a evolutionary effectInteraction of rotation and pulsation?Interaction of convection and pulsation?
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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
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Amplitude variation also be found in HS 0507+0434B(See the Poster of Fu et al.)
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Power Spectrum (Dec 2009 + Jan 2010)
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42 Periods were resolved.However, it is very difficult to do the mode identification
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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)
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Vielen Dank!