Observations of the ZZ Ceti star KUV Chun Li Beijing Normal University

Overview Introduction of ZZ Ceti stars New observations for KUV Data Reduction Preliminary Results Future Work

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.

Pure instability strip

Stucture of White Dwarfs

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

ZZ Ceti Star KUV 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 )

Journal of new observations in B DateObservatoryTelescopeFlames Feb Lijiang2.40m6805 Dec Xinglong2.16m1651 Dec Lijiang2.40m2328 Dec Xinglong2.16m815 Jan SPM1.50m2771 Jan Xinglong2.16m2745

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 Freq Err Ampl Err S/N Freq Err Ampl Err S/N

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= M ⊙

Light Curve(Dec 2009 part 1)

Light curve(Dec 2009 Part 2)

Light Curve(Jan 2010)

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

Thanks!