engleski

Phase Dispersion Minimisation as a tool for analysis of long-term brightness variations in light curves

Long-period variables such as Mira stars often show long-term variations in brightness superimposed on their periodic changes caused by pulsations. Long-term variations can be periodic or non-periodic, caused by orbital motion, presence of dust or by some other physical mechanism. In order to remove periodic short-term variations and study only the long-term component, we propose Phase dispersion minimisation (PDM) method as an efficient tool and a method of choice. PDM is a very robust and precise method, capable of efficiently removing short-term periodic variations regardless of the shape of the light curve. It greatly reduces the number of free fitting parameters usually used by other techniques as the pulsation period is the only parameter to be determined. If the phase diagram is fitted to the Fourier polynomial, other pulsational parameters can be also determined. We have successfully applied PDM method in analysis of light curves of symbiotic Miras HM Sge and RR Tel, and compared the results with the values obtained by Discrete Fourier Transform (DFT), another widely used method. Our results show that PDM method is efficient in reducing the light curves for short-term periodic variations and can be applied in larger stellar samples expected to be obtained by surveys such as LSST.

AGB stars, variable stars, numerical methods

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