On the kinematic state of the atmosphere within IRAS 07430+1115 system

Having obtained high-resolution optical spectra with the NES spectrograph of the 6-m telescope BTA, we investigated the variability of the spectral features and radial velocity for a cold star which passed the asymptotic branch of giants and is associated with the IRAS 07430+1115 source. The optical spectrum of this post-AGB star with altered chemical composition is purely absorbtional, emissions and other peculiarities are absent in the spectrum. From the measurements of the positions of many metal absorbtions (mainly ions of heavy $s$-process metals) a weak variability of the radial velocity was revealed. The velocity varies with the average value $V_r=37.0$ km/s and the standard deviation $\Delta V_r \approx 0.8$ km/s, which may be a consequence of low-amplitude pulsations in the atmosphere of a far evolved star. The position of the H$\alpha$ line core varies within 40.5–43.8 km/s. Based on measurements of the positions of the rotational components of the (0;0), (1;0) and (2;0) Swan bands of the molecule C$_2$ origin in the circumstellar envelope, the average radial velocity $V_r{\rm (Swan)}=21$ km/s and the expansion velocity typical for post-AGB stars envelope $V_{\rm exp} \approx 16$ km/s are determinated. Using the intensity of the infrared triplet of oxygen, we estimated the luminosity of the central star of the IRAS 07430 system $\log L/L_{\odot} \approx 3.1$ which is within the range of values for post-AGB stars.