MAVKA: Program Of Statistically Optimal Determination Of Phenomenological Parameters Of Extrema. Parabolic Spline Algorithm and Analysis of Variability of the Semi-Regular Star Z UMa

TL;DR

This paper introduces MAVKA software with a novel parabolic spline algorithm for analyzing extrema in variable star brightness, demonstrating its effectiveness on the semi-regular star Z UMa and highlighting its broader signal analysis potential.

Contribution

A new parabolic spline algorithm with adjustable boundaries is proposed, enhancing the analysis of extrema and variability in astrophysical signals beyond traditional methods.

Findings

Analysis of Z UMa reveals multiple periodic oscillations.

The new spline method improves extrema approximation accuracy.

Significant variability in amplitudes and phases of oscillations is detected.

Abstract

Advanced MAVKA software for the approximation of extrema observations is used to analyze the variability of the brightness of pulsating and eclipsing stars, but may be useful in analyzing signals of any nature. A new algorithm using a parabolic (quadratic) spline is proposed. In contrast to the traditional definition of a spline as a piecewise-defined function at fixed intervals, a spline is proposed to be divided into three intervals, but the positions of the boundaries between the intervals are additional parameters. The spline defect is 1, that is, the function and its first derivative are continuous and the second derivative can be discontinuous at the boundaries. Such a function is an enhancement of the "asymptotic parabola" (Marsakova and Andronov 1996). The dependence of the fixed signal approximation accuracy on the location of the boundaries of the interval is considered. The parameter accuracy estimates using the least squares method and bootstrap are compared. The variability of the semi-regular pulsating star Z UMa is analyzed. The presence of multicomponent variability of an object, including, four periodic oscillations and significant variability of the amplitudes and phases of individual oscillations is shown.