Photometric and spectral variability of the candidate post-AGB star IRAS 07506-0345

Abstract

We report photometric and spectroscopic observations of the poorly studied post-AGB candidate IRAS 07506-0345, obtained with the telescopes of the Caucasian Mountain Observatory of SAI MSU in 2023-2026. The star exhibits Cepheid-like variability with a pulsation period of P = 33.68 days. Low-resolution spectra reveal a strong CN molecular band at $λ$ 3883, characteristic of carbon-rich post-AGB objects, while H$α$ shows phase-dependent emission and P~Cyg-type profiles, indicating shock waves and mass outflow. Radial velocities are measured from multiple spectral lines. Using period-luminosity-color relations for Type II Cepheids, we estimate a luminosity of $L = 1050\pm250\,L_\odot$. The combined properties - period, amplitude, light-curve morphology, infrared excess, low metallicity, and hydrogen line emissions - securely classify IRAS 07506-0345 as an RV Tau variable.