On measuring low-degree p-mode frequency splitting with full-disc integrated data |
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| Authors: | T Appourchaux H-Y Chang D O Gough T Sekii |
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| Institution: | ESA/ESTEC, PO Box 299, 2200 AG, Noordwijk, the Netherlands;Korea Institute for Advanced Study, 207-43 Cheongryangri-dong Dongdaemun-gu, Seoul 130-012, Republic of Korea;Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA;Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge CB3 9EW;Department of Physics, HEPL Annex B208, 455 Via Palou, Stanford, CA 94305-4085, USA |
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| Abstract: | The standard method of measuring rotational splitting from solar full-disc oscillation data, based on maximum-likelihood fitting of multi-Lorentzian profiles to oscillation power spectra, systematically overestimates the splitting. One of the reasons is that the maximum likelihood estimators (MLE) become unbiased only asymptotically as the number of data tends to infinity; for a finite data set they are often biased, inducing a systematic error. In this paper we assess by Monte Carlo simulations the amount of systematic error in the splitting measurement, using artificially generated power spectra. The simulations are carried out for multiplets of degree  2 and 3 with various signal-to-noise ratios, linewidths and observing times. We address the possible use of non-MLE estimators that could provide a smaller or negligible systematic error. The implication for asteroseismology is also discussed. |
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| Keywords: | methods: data analysis Sun: oscillations |
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