16.20 o10 p chote
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Transcript of 16.20 o10 p chote
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
Time Series Photometry of Pulsating WhiteDwarf Stars
P. Chote D.J. Sullivan
School of Chemical and Physical SciencesVictoria University of Wellington
NZIP Conference 2011
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
Outline
Pulsating White DwarfsWhat?How?Why?
Puoko-nui CCD PhotometerInstrumentData ReductionExample
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
What?How?Why?
What are White Dwarfs?
I Slowly cooling stellar remnantafter nuclear fusion ceases
I 98% of stars end their life asWhite Dwarfs
I Very faint (difficult to observe)
I First pulsating white dwarfdiscovered accidentally in 1967(Landolt, ApJ, 1968)
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
What?How?Why?
How do they pulsate?
I Complex internal interactions
I Non-radial G-mode pulsations(like water waves)
I Changing Density→Temperature→ Luminosity
I Described by sphericalharmonics that evolve with time
I Periods of 100 - 1000 seconds
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
What?How?Why?
How do they pulsate?
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
What?How?Why?
Why study them?
I Pulsation modes sample internalstructure
I Asteroseismology!
I Laboratories for extreme & exoticphysics
I Core compositionI Convection zone informationI Neutrino coolingI Age determinationsI ...
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
InstrumentData ReductionExample
Instrument Overview
I Puoko-nui: “Big Sensor”
I 1024x1024px shutterlessFrame Transfer CCD
I ∼ 6 × 6 arcmin field of view
I GPS timing
I Autoguiding
I Portable
I Online data reduction
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
InstrumentData ReductionExample
Mount John University Observatory
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
InstrumentData ReductionExample
Frame Transfer
I CCD Readout is slow
I Mask half the chip from light
I Shift charge into masked areaand readout in parallel with nextexposure
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
InstrumentData ReductionExample
Instrument Overview
TimeDownload
Monitor Configure
Frames
Time
Guiding
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
InstrumentData ReductionExample
Instrument Overview
Imaging CCD +
Thermo-electric Cooler
Guide
Camera
Control
Electronics
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
InstrumentData ReductionExample
Instrument Overview
Guide + AcquisitionComputers
To GPSReceiver
ControllerUnit
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
InstrumentData ReductionExample
Instrument Overview
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
InstrumentData ReductionExample
Data reduction
T
I
F
I
Converting the raw CCD frames to ameasure of brightness vs time
1. Preprocessing
2. Aperture Photometry
3. Fourier Analysis
4. Modelling
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
InstrumentData ReductionExample
Preprocessing
Raw CCD Frame Processed CCD Frame
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
InstrumentData ReductionExample
Aperture Photometry
1. Determine aperture size
2. Estimate & subtract skyintensity (blue annulus)
3. Center aperture over star
4. Sum pixel intensities insideaperture (red circle)
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
InstrumentData ReductionExample
Lightcurve
I Measurement of intensity vs time
I Divide pulsating star intensity bycomparison to atmosphericeffects
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
InstrumentData ReductionExample
Fourier AnalysisI Any periodic signal can be
represented as a sum of sinewaves
I The Fourier Transform tells youthe frequency components in agiven signal
I Peaks in FT tell us thefrequencies of the pulsationmodes in the WD
I More data = better identificationof frequencies
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
InstrumentData ReductionExample
Fourier AnalysisI Any periodic signal can be
represented as a sum of sinewaves
I The Fourier Transform tells youthe frequency components in agiven signal
I Peaks in FT tell us thefrequencies of the pulsationmodes in the WD
I More data = better identificationof frequencies
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
InstrumentData ReductionExample
EC04207-4748: 30 July 2011
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
InstrumentData ReductionExample
EC04207-4748
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
InstrumentData ReductionExample
EC04207-4748
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
InstrumentData ReductionExample
I Determine ‘real’ frequenciesI Combination frequenciesI Rotational splitting
I Constraints on numerical models
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
Summary
I Pulsating White Dwarfs areinteresting objects
I Pulsations constrain internalstructure
I Specialised instruments forobserving
I Data reduction to determinefrequencies
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars
Pulsating White DwarfsPuoko-nui CCD Photometer
Summary
Acknowledgements
I Marsden Fund
I University of Canterbury
P. Chote, D.J. Sullivan Time Series Photometry of Pulsating White Dwarf Stars