Wednesday, June 26, 2013

1306.5923 (Tapas Baug et al.)

Noise reduction methods in analysis of near infrared lunar occultation light curves for high angular resolution measurements    [PDF]

Tapas Baug, Thyagarajan Chandrasekhar
Lunar occultation (LO) technique in the near-infrared provides angular resolution down to milliarcseconds on the occulted source even with ground-based 1m class telescopes. LO observations are limited to brighter objects because they require high signal to noise ratio (S/N ~ 40) for proper extraction of angular diameter values. Hence, methods to improve the S/N ratio by reducing noise using Fourier and Wavelet transforms have been explored in this study. A sample of 54 near-infrared LO light curves observed with IR Camera at Mt Abu observatory has been used. It is seen that both Fourier and Wavelet methods have shown improvement in S/N, compared to the original data. However, the application of wavelet transforms results in slight smoothening of the fringes resulting in a higher angular diameter value. Fourier transforms which reduce discrete noise frequencies do not distort the fringe. Fourier transform method seems to be effective in S/N improvement, as well as improved model fit particularly in the fainter regime of our sample. They also provide a better model fit for brighter sources in some cases though there may not be significant S/N improvement.
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