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

TL;DR

This study provides extensive multi-decade photometric data on the post-AGB star IRAS 22272+5435, revealing pulsation periods, dust formation episodes, and spectral anomalies, offering insights into late stellar evolution and dust ejection processes.

Contribution

It presents the first long-term JHKLM photometry analysis of IRAS 22272+5435, linking dust emission increases to a recent mass ejection event and analyzing pulsation and spectral variations.

Findings

Detected two close pulsation periods of 127 and 132 days.

Observed increased KLM-band brightness indicating dust emission from 1996 to 2004.

No strong optical variability suggests a specific dust ejection geometry or optical depth.

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.