Instability in the System of the Distant Post-AGB Star LS III +52°24 (IRAS 22023+5249)

Abstract

The optical spectra of the B-supergiant LS III +52°24 (IRAS 22023+5249) obtained at the 6-m BTA telescope with a resolution ${R} ≥slant 60{\kern 1pt} {\kern 1pt} 000$ in 2010-2021 revealed signs of wind variability and velocity stratification in the extended atmosphere. The neutral hydrogen lines H$α $ and H$β $ have a P Cyg profile; their wind absorption component changes position in the range from ${{V}_{ \odot }} = - 270$ to $ - 290$ km/s. The H$α $ emission intensity reaches record-high values with respect to the local continuum: $I{/}{{I}_{{{cont}}}} ≥slant 70$. The stationary radial velocity according to the positions of symmetric forbidden emissions and pemitted metal emissions is taken as the systemic velocity ${{V}_{{{sys}}}} = - 149.6 ± 0.7$ km/s. For the first time for this star, a time variability of the radial velocity in the range from ${{V}_{ \odot }} = - 127.2$ to $ - 178.3$ km/s was found based on the positions of absorptions of NII and OII ions, which indicates the possible presence of a companion and/or atmospheric pulsations. The variability of the oxygen triplet profile $W$(OI 7774) due to the appearance of unstable emission was recorded. The set of interstellar absorptions of the NaI D-line profile in the range from ${{V}_{ \odot }} = - 10.0$ to $ - 167.2$ km/s is formed in the Local Arm and subsequent arms of the Galaxy. The distance to the star, $d > 5.3$ kpc, combined with the high velocity indicates that the star is located in the interarm space of the Galaxy beyond the Scutum-Crux arm.