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

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⩾ 60 1pt 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_⊙ = - 270 to - 290 km/s. The H α emission intensity reaches record-high values with respect to the local continuum: I/I_cont⩾ 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_⊙ = - 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_⊙ = - 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.