# Light Curve Parameters of Cepheid and RR Lyrae Variables at Multiple Wavelengths $-$ Models vs. Observations

## TL;DR

This study compares observed and theoretical light curves of Cepheid and RR Lyrae stars across multiple wavelengths, highlighting discrepancies and suggesting improvements in stellar pulsation models based on Fourier analysis.

## Contribution

It provides a detailed comparison between models and observations of variable star light curves, emphasizing the need for refined input physics in pulsation codes.

## Key findings

- RR Lyrae amplitude and Fourier parameters mostly match observations except at low metallicity.
- Cepheid models show larger deviations from observations, especially in amplitude.
- Increasing convective efficiency in models reduces discrepancies.

## Abstract

We present results from a comparative study of light curves of Cepheid and RR Lyrae stars in the Galaxy and the Magellanic Clouds with their theoretical models generated from the stellar pulsation codes. Fourier decomposition method is used to analyse the theoretical and the observed light curves at multiple wavelengths. In case of RR Lyrae stars, the amplitude and Fourier parameters from the models are consistent with observations in most period bins except for low metal-abundances ($Z<0.004$). In case of Cepheid variables, we observe a greater offset between models and observations for both the amplitude and Fourier parameters. The theoretical amplitude parameters are typically larger than those from observations, except close to the period of $10$ days. We find that these discrepancies between models and observations can be reduced if a higher convective efficiency is adopted in the pulsation codes. Our results suggest that a quantitative comparison of light curve structure is very useful to provide constraints for the input physics to the stellar pulsation models.