"Asymptotic Parabola" Fits for Smoothing Generally Asymmetric Light Curves

TL;DR

This paper introduces a Windows-based program for fitting 'Asymptotic Parabolas' to asymmetric light curves, improving the analysis of pulsating stars by providing statistically optimal, continuous approximations.

Contribution

The paper presents a new user-friendly Windows program implementing the 'Asymptotic Parabola' fit, extending previous DOS-based methods for analyzing asymmetric light curves of variable stars.

Findings

Effective for pulsating variables with asymmetric maxima and minima

Applicable to both asymmetric and symmetric light curves

Enhanced computational capacity with Windows interface

Abstract

A computer program is introduced, which allows to determine statistically optimal approxi-mation using the "Asymptotic Parabola" fit, or, in other words, the spline consisting of polynomials of order 1,2,1, or two lines ("asymptotes") connected with a parabola. The function itself and its derivative is continuous. There are 5 parameters: two points, where a line switches to a parabola and vice versa, the slopes of the line and the curvature of the parabola. Extreme cases are either the parabola without lines (i.e.the parabola of width of the whole interval), or lines without a parabola (zero width of the parabola), or "line+parabola" without a second line. Such an approximation is especially effective for pulsating variables, for which the slopes of the ascending and descending branches are generally different, so the maxima and minima have asymmetric shapes. The method was initially introduced by Marsakova and Andronov (1996OAP.....9..127M) and realized as a computer program written in QBasic under DOS. It was used for dozens of variable stars, particularly, for the catalogs of the individual characteristics of pulsations of the Mira (1998OAP....11...79M) and semi-regular (200OAP....13..116C) pulsating variables. For the eclipsing variables with nearly symmetric shapes of the minima, we use a "symmetric" version of the "Asymptotic parabola". Here we introduce a Windows-based program, which does not have DOS limitation for the memory (number of observations) and screen resolution. The program has an user-friendly interface and is illustrated by an application to the test signal and to the pulsating variable AC Her.