Cutoff frequencies and noise power law model of spectral density:adaptation of the multivariance method for irregularly spaced timingdata using the lowest-mode estimator approach

摘要

The concept of structure functions, which is an extension of thenvariance approach, is useful to determine the variance (the structurenfunction) which is optimized for a type of noise and for an order ofndrift. The multivariance method was developed to use different variancesnover the same signal. It is then possible to select a set of variancesnin which each variance is optimized to the determination of onenparameter (of one noise level, drift, or cutoff frequency). Recently, wenadapted this method to irregularly spaced timing data. In thisnconnection, we replaced the structure functions by another method ofnspectral density estimation: the lowest-mode estimator, introduced bynJ.E. Deeter and P.E. Boynton (1982, 1984) for the analysis of pulsarntiming data. Different lowest-mode estimators can be constructednaccording to two priorities: the order of drifts that must be removednand the type of noise for which the sensitivity must be maximum. Thus, anmultivariance system is developed using a set of different estimators.nThe details of this method are described, and the results for differentnsignals are discussed in this paper