Download Time Domain Astrophysics in South Africa 2

Time Domain Astrophysics in
South Africa 2
Astero-seismology
Astero-seismology
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• 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
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
Probing a star with seismic
waves
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
Search for new Pulsating stars
• Rapidly Oscillating
Ap stars (SAAO)
5 min < Ppuls<16 min
Frequency Spectrum
like nothing you
have ever seen
dipole(-like)
new, improved
mode
strange doublet
Pulsating sdB stars
• hot Horizontal
Branch stars with
temperatures of
about 30,000 K
• Periods 2 -3 minutes
Observational Facilities
• Photo-electric photometers
• CCDs (also have frame-transfer)
• Giraffe spectrograph {R = 39000,
wavelength 3820 - 9240 angstrom, V <
9}
• SALT ?
Theory
• Non-linear theory (SAAO)
• Radiative Transfer and Oscillations in A stars
(UCT/SAAO)