Time/frequency analysis of some MOST data F. Baudin (IAS) & J. Matthews (UBC)
Just few words about time/frequency analysis Classical Fourier transform: FT[S(t)]( )= S(t) e i t dt Windowed Fourier transform: WFT[S(t)]( ,t 0 ) = S(t) W(t-t 0 ) e i t dt If W(t) = gaussian => Gabor transform If W(t, ) => wavelet transform
Just a drawing about time/frequency analysis
MOST data Equ [roAp] Oph [red giant] Boo [Post MS] Procyon [MS]
Equ : a simple case?
Equ : a simple case of beating Confirmation with simulation: modulation due to beating
Oph : a more interesting case
Signal + sine wave of constant amplitude => noise estimation
Oph : a more interesting case Temporal modulation not due to noise: which origin?
[ Boo] Noise : not so interesting but…
Instrumental periodicities (CCD temperature?)
Procyon: variability of the signal?
Procyon: variability of the signal T < 10 days T > 10 days
Procyon: variability of the signal T < 10 days T > 10 days
Conclusion Time/Frequency analysis allows : variation with time of the (instrumental) noise [ Boo, Procyon] simple interpretation (beating) of amplitude modulation [ Equ] evidence of temporal variation of modes of unknown origin [ Oph]
[Procyon] Noise : not so interesting but…