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Time Domain Astrophysics in South Africa 2

Time Domain Astrophysics in South Africa 2. Astero-seismology. Astero-seismology. Monitoring Time variations in intrinsic variables in order to infer their properties such as mass, luminosity, rotation rate, internal composition. Seismic Waves trapped in Stars. Stars pulsate according to

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Time Domain Astrophysics in South Africa 2

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  1. Time Domain Astrophysics in South Africa 2 Astero-seismology

  2. Astero-seismology • Monitoring Time variations in intrinsic variables in order to infer their properties such as mass, luminosity, rotation rate, internal composition

  3. Seismic Waves trapped in Stars • Stars pulsate according to y=An( r ) Ylm (theta, phi) exp(-omega t) Where n l m describe a mode A good start to astero-seismology is in determining these for as many modes as possible

  4. Probing a star with seismic waves

  5. Asteroseismology Research in South Africa • Observational Studies include - mode identification using photometry alone (determines l) - mode identification using Baade-Wesselink methods (combination) - mode-identification by observing line profile variations On roAp stars, delta Scuti, sdB stars, beta Cepheid etc

  6. Search for new Pulsating stars • Rapidly Oscillating Ap stars (SAAO) 5 min < Ppuls<16 min

  7. like nothing you have ever seen dipole(-like) new, improved mode strange doublet Frequency Spectrum

  8. Pulsating sdB stars • hot Horizontal Branch stars with temperatures of about 30,000 K • Periods 2 -3 minutes

  9. Observational Facilities • Photo-electric photometers • CCDs (also have frame-transfer) • Giraffe spectrograph {R = 39000, wavelength 3820 - 9240 angstrom, V < 9} • SALT ?

  10. Theory • Non-linear theory (SAAO) • Radiative Transfer and Oscillations in A stars (UCT/SAAO)

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