Instabilities of the kinematic state of the atmospheres of some single C-rich post-AGB stars

TL;DR

This study investigates atmospheric instabilities in certain post-AGB stars using high-resolution spectroscopy, revealing pulsations, profile asymmetries, and velocity stratification, which enhance understanding of their atmospheric dynamics.

Contribution

The paper provides new observational evidence of atmospheric instabilities and stratification in post-AGB stars, utilizing long-term high-resolution spectroscopy to analyze their pulsations and velocity fields.

Findings

Detected low-amplitude pulsations in several stars.

Observed splitting and asymmetry in absorption profiles.

Estimated stellar luminosities consistent with post-AGB status.

Abstract

To search for and study the instabilities in the atmospheres of selected post-AGB stars, we have performed a long-term high-resolution spectroscopy (R=60000) with the spectrograph NES of the 6-meter BTA telescope. Low-amplitude pulsations, splitting and/or asymmetry of the absorption profiles with a low excitation potential, as well as variability of a complex H$\alpha$ profile have been registered in the optical spectra of single stars associated with the IR sources IRASz02229+6208, IRAS 04296+3429, IRAS 07134+1005, IRAS 07430+1115, IRAS 19500-1709, IRAS 22223+4327, and IRAS 23304+6147 that had previously undergone the 3-d dredge-up. The maximum pulsation amplitude A$_{\rm Vr}$ was detected for the stars in the IRAS 07134+1005 and IRAS 19500-1709 systems, which have the maximum temperatures among the stars studied. Stratification of radial velocity in the atmosphere was found for two stars in the sample. The luminosity of the studied stars was estimated based on the intensity of the IR oxygen triplet OI(7774). Moreover, a luminosity of log${\rm (L/L_{\odot})}\approx$3.1 was obtained for the star in the IRAS 07430+1115 system within the typical values for post-AGB stars luminosity, which eliminates the paradox of the luminosity and the initial mass of this object.