Approximating RR Lyrae light curves using cubic polynomials

TL;DR

This paper introduces a cubic polynomial method for approximating RR Lyrae light curves, reducing ringing effects and parameters compared to Fourier methods, and uncovers new periodicities in HST data of M31 halo RR Lyrae stars.

Contribution

The paper presents a novel cubic polynomial approach for light curve approximation that outperforms Fourier decomposition in reducing ringing and parameter count.

Findings

Eliminates ringing effects in light curve approximation

Identifies 23 RRc, 29 RRab, and 3 multiperiodic stars in HST data

Uses fewer parameters than Fourier method

Abstract

In this paper, we use cubic polynomials to approximate RR Lyrae light curves and apply the method to HST data of RR Lyraes in the halo of M31. We compare our method to the standard method of Fourier decomposition and find that the method of cubic polynomials eliminates virtually all ringing effects and does so with significantly fewer parameters than the Fourier technique. Further, for RRc stars the parameters in the fit are all physical. Our study also reveals a number of additional periodicites in this data not found previously: we find 23 RRc stars, 29 RRab stars and 3 multiperiodic stars.