Multiwavelength study of observed and predicted pulsation properties of first overtone Cepheids in the Magellanic Clouds

ABSTRACT We present a detailed analysis of the light curves and pulsation properties of first overtone (FO) Cepheids in the Magellanic Clouds (MCs) obtained using observations and predictions from stellar pulsation models. Multiwavelength observational light curves were compiled from the literature (OGLE-IV, Gaia, and VMC). We investigate the period–amplitude (PA), period–colour (PC), period–luminosity (PL), and amplitude–colour (AC) relations for FO Cepheids at multiwavelengths. We find that the PA distribution of FO Cepheids in the MCs modelled using a Gaussian Mixture Model shows that the Small Magellanic Cloud (SMC) consists of higher amplitude stars than the Large Magellanic Cloud (LMC). We find multiple break-points in the PC/PL/AC relations for FO/fundamental Cepheids in the optical and near-infrared bands including the one near to $P=2.5$ d in the MCs, using piecewise regression analysis and F-test statistics. Similarly, for the LMC FO Cepheids, we find a break-point in the PC/PL/AC relations near $P=0.58$ d. The slopes of the PC relations for LMC FO Cepheids are found to be shallow for $0.58<P(\rm d)< 2.5$ but steeper for $P< 0.58$ d and $P>2.5$ d. We complemented the observed relations using theoretical models for FO Cepheids with chemical compositions $Z= 0.008$ and $Z = 0.004$, appropriate for the LMC and SMC, respectively, computed with mesa-rsp. Our results show that the pulsation properties of FO Cepheids in PC/PL/AC relations and colour–magnitude diagram are strongly correlated and their connections can provide stringent constraints for the theoretical pulsation models.