Polarization and a Model for the Dust Shell of the Carbon-rich post-AGB Object IRAS 22272$$+$$5435 (V354 Lac)

We present the observations of the carbon-rich post-AGB object IRAS 22272 $$+$$ 5435 performed in the 550, 625, and 880 nm bands by the method of differential speckle polarimetry with the 2.5-m telescope of the Caucasus Mountain Observatory. A shell has been detected at an angular distance of $$1^{\prime\prime}$$ from the star in all bands. The infrared (IR) source IRAS 22272 $$+$$ 5435 is associated with the semiregular variable star V354 Lac. Apart the quasi-periodic variability caused by pulsations, an increase in the near-IR ( $$KLM$$ ) brightness due to an additional dust ejection was observed in the period from 1996 to 2004 (Ikonnikova et al. 2025). We have constructed a model of the circumstellar dust shell that reproduces well (within the adopted model assumptions) the observed spectral energy distribution and the polarized flux distribution in the visible range. The model is consistent with the observations performed by the method of differential speckle polarimetry in 2020. We have obtained the following parameters of the star and its dust shell. For the distance $$d=1410$$ pc derived from the Gaia DR3 parallax the luminosity of the star is $$L=6600\,L_{\odot}$$ . The dust shell in our model consists of four components formed by the isotropic wind and the superwind at the AGB stage as well as by the isotropic wind and the equatorial ejection at the post-AGB phase. The dust masses in these shells are $$3\times 10^{-9}$$ , $$6.9\times 10^{-7}$$ , $$3\times 10^{-4}$$ , and $$1.3\times 10^{-4}\,M_{\odot}$$ , respectively. The increase in the IR flux in 1996–2004 is explained in the model by the separate ejection of a dust cloud with a mass of $$6\times 10^{-10}\,M_{\odot}$$ whose velocity is estimated to be 60 km s $${}^{-1}$$ .