Bibcode
Jiménez-Reyes, S. J.; Chaplin, W. J.; García, R. A.; Appourchaux, T.; Baudin, F.; Boumier, P.; Elsworth, Y.; Fletcher, S. T.; Lazrek, M.; Leibacher, J. W.; Lochard, J.; New, R.; Régulo, C.; Salabert, D.; Toutain, T.; Verner, G. A.; Wachter, R.
Referencia bibliográfica
Monthly Notices of the Royal Astronomical Society, Volume 389, Issue 4, pp. 1780-1790.
Fecha de publicación:
10
2008
Número de citas
12
Número de citas referidas
9
Descripción
We report on the results of the latest solarFLAG hare-and-hounds
exercise, which was concerned with testing methods for extraction of
frequencies of low-degree solar p modes from data collected by
Sun-as-a-star observations. We have used the new solarFLAG simulator,
which includes the effects of correlated mode excitation and
correlations with background noise, to make artificial time-series data
that mimic Doppler velocity observations of the Sun-as-a-star. The
correlations give rise to asymmetry of mode peaks in the frequency power
spectrum. 10 members of the group (the hounds) applied their
`peak-bagging' codes to a 3456-d data set, and the estimated mode
frequencies were returned to the hare (who was WJC) for comparison.
Analysis of the results reveals a systematic bias in the estimated
frequencies of modes above ~1.8mHz. The bias is negative, meaning the
estimated frequencies systematically underestimate the input
frequencies.
We identify two sources that are the dominant contributions to the
frequency bias. Both sources involve failure to model accurately subtle
aspects of the observed power spectral density in the part (window) of
the frequency power spectrum that is being fitted. One source of bias
arises from a failure to account for the power spectral density coming
from all those modes whose frequencies lie outside the fitting windows.
The other source arises from a failure to account for the power spectral
density of the weak l = 4 and 5 modes, which are often ignored in
Sun-as-a-star analysis. The Sun-as-a-star peak-bagging codes need to
allow for both sources, otherwise the frequencies are likely to be
biased.
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Savita
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