IRAS 22272+5435 (V354 Lac): Multicolor Photometry of a Variable Carbon-rich Post-AGB Star and a Dust Formation Episode

Abstract

We present new \(UBV\) photometric observations (2009–2024) of the carbon-rich post-AGB star IRAS 22272+5435 (V354 Lac), combined with our data spanning over 30 years (1991–2024). The star shows pulsations with two closely spaced periods, 127 and 132 d, which cause brightness variations of variable amplitude. We also detect low-amplitude oscillations with a 661-day period, of uncertain origin. Color analysis reveals both temperature variations during pulsations and spectral anomalies. For the first time, we analyze long-term \(JHKLM\) photometry (1994–2024), showing increased \(KLM\)-band brightness from 1996 to 2004—likely due to dust emission following a sudden mass ejection. The absence of strong optical variability suggests either a large angle between the ejection direction and the line of sight or a low optical depth of the ejected material. We discuss possible mechanisms and observational signatures of this dust-formation event.