Variability of physical parameters of IRAS 22272\(+\)5435 during the pulsation cycle

Abstract

A time series of high-resolution spectra in the optical wavelength region was used to examine the variability of physical parameters of the early-stage post-AGB star IRAS 22272\(+\)5435. Excitation balance analysis for a sample of iron (Fe), cerium (Ce), and neodymium (Nd) lines confirms effective temperature changes from about \(5100\pm 150\) to \(5750\pm 100\) K during the 132-day pulsation cycle. Using the method of ionization balance, we observed a minor change in surface gravity between \(\log g= 0.5\) and \(0.7\pm 0.3\) (cgs). The microturbulent velocity does not change within the uncertainty limits, \(\xi _t=4.5\pm 0.5\) km s\(^{-1}\). Large macroturbulence in the range of 20–25 km s\(^{-1}\) was found. We observed variable intensity of the oxygen (O) infrared triplet at 7771-5 Å  which is most likely due to changes in luminosity during the pulsation cycle.