Issue |
Astron. Astrophys. Suppl. Ser.
Volume 132, Number 1, October I 1998
|
|
---|---|---|
Page(s) | 121 - 132 | |
DOI | https://doi.org/10.1051/aas:1998440 | |
Published online | 15 October 1998 |
The art of fitting p-mode spectra
II. Leakage and noise covariance matrices
1
Space Science Department of ESA, ESTEC, NL-2200 AG Noordwijk, The Netherlands
2
Teoretisk Astrofysik Center, Århus Universitet, DK-8000 Århus C, Denmark
3
W.W. Hansen Experimental Physics Laboratory, Center for Space Science and Astrophysics, Stanford University, Stanford, CA 94305-4085, U.S.A.
Received:
15
October
1997
Accepted:
24
March
1998
In Part I we have developed a theory
for fitting p-mode Fourier spectra assuming that these spectra have a
multi-normal distribution. We showed, using Monte-Carlo simulations,
how one can obtain p-mode parameters using "Maximum Likelihood
Estimators". In this article, hereafter Part II, we show how to use the
theory developed in Part I for fitting real data. We introduce 4 new
diagnostics in helioseismology: the echelle
diagram, the cross echelle diagram, the inter echelle diagram,
and the cross spectrum ratio.
These diagnostics are extremely powerful to visualize and understand
the covariance matrices of the Fourier spectra, and also to find
bugs in the data analysis code. The diagrams are used to verify the
computation of the leakage matrices, and also to measure quantitatively
these matrices. Cross spectrum ratios are used to obtain quantitative
information on the noise covariance matrices. Numerous examples using the
LOI/SOHO and GONG data are given.
Key words: methods: data analysis / statistical / observational / Sun: oscillations
© European Southern Observatory (ESO), 1998