2026A&A...705A.186D

Context. A major challenge in modeling classical Cepheids is the treatment of convection, particularly its complex interplay with pulsation. This inherently three-dimensional (3D) process is typically approximated in one-dimensional (1D) hydrocodes, using dimensionless turbulent convection (TC) free parameters. Calibrating these parameters is essential for reproducing key observational features, such as the light curve amplitudes, secondary bumps, and the red edge of the instability strip (IS).
Aims. In this work, we calibrate the TC parameters adopted from the publicly available Modules for Experiments in Stellar Astrophysics-Radial Stellar Pulsations (MESA-RSP) code. We carried out a comparison using both the observational data of classical Cepheids and stellar parameter constraints from the Stellingwerf code. This is one of the few codes currently available that are capable of replicating a wide range of observed features of the classical pulsators.
Methods. We computed the multiband (V, I, and K_s) MESA-RSP light curves for 18 observed Large Magellanic Cloud (LMC) Cepheids, using stellar parameters determined on the basis of Stellingwerf's code. By fine-tuning the mixing-length and eddy viscosity parameters, we calibrated the TC treatment in MESA-RSP. We compared the resulting period-luminosity (PL), period-radius (PR), and period-mass-radius (PMR) relations with the prediction of Stellingwerf's model.
Results. We successfully reproduced the multiband (V, I, and K_s) light curves for 18 observed LMC Cepheids using the stellar parameters determined with Stellingwerf's code. We also finetuned the mixing-length and eddy viscosity parameters in MESA-RSP. Our models yielded PL, PR, and PMR relations that were consistent with the previous results. Interestingly, although our results are broadly in agreement with previous works, we explicitly identified distinct mass-luminosity (ML) relations for fundamental-mode (FU) and first-overtone (FO) Cepheids for the first time. This suggests that the macroscopic phenomena affecting the ML relation depend on the stellar mass itself and/or on the effective temperature range. Our investigation is focused on the calibration of the TC parameters, but we did not find a single set of convective parameter values that was sufficient to reproduce all the light curves. In addition, no statistically significant correlation was found between the stellar properties (e.g., the effectives temperature or the stellar mass) and the convection parameters, although subtle trends for the period and effective temperature have been noted. As for the inferred Cepheid distances, our application of the model-fitting technique yields reddened distance moduli, in good agreement with those reported in previous works. This result is not surprising, given that we adopted the same input stellar parameters, with only minor differences in the adopted model atmospheres.