Post-AGB candidate IRAS 02143+5852: Cepheid-like variability, three-layer circumstellar dust envelope and spectral features

Abstract

We present the results of multicolour UBVRCICJHK photometry, spectroscopic analysis and spectral energy distribution (SED) modelling for the post-AGB candidate IRAS 02143+5852. We detected Cepheid-like light variations with the full peak-to-peak amplitude ΔV ∼ 0.9 mag and the pulsation period of about 24.9 d. The phased light curves appeared typical for the W Vir Cepheids. The period-luminosity relation for the Type II Cepheids yielded the luminosity log L/L⊙ ∼ 2.95. From a low-resolution spectrum, obtained at maximum brightness, the following atmospheric parameters were determined: Teff ∼ 7400 K and log g ∼ 1.38. This spectrum contains the emission lines Hα, ${\rm Ba\, \small {II}}$ λ6496.9, ${\rm He\, \small {I}}$λ10830 and Paβ. Spectral monitoring performed in 2019–2021 showed a significant change in the Hα profile and appearance of CH and CN molecular bands with pulsation phase. The metal lines are weak. Unlike typical W Vir variables, the star shows a strong excess of infrared radiation associated with the presence of a heavy dust envelope around the star. We modelled the SED using our photometry and archival data from different catalogues and determined the parameters of the circumstellar dust envelope. We conclude that IRAS 02143+5852 is a low-luminosity analogue of dusty RV Tau stars.