The high-resolution ( R \sim 48 000 ) optical spectrum of the B-type supergiant LS 5112 , identified as the optical counterpart of the post-AGB candidate IRAS 18379–1707 is analysed .
We report the detailed identifications of the observed absorption and emission features in the wavelength range 3700-9200 Å for the first time .
The absorption line spectrum has been analysed using non-LTE model atmosphere techniques to determine stellar atmospheric parameters and chemical composition .
We estimate T _ { \text { eff } } = 18 ~ { } 000 \pm 1000 K , \log g = 2.25 \pm 0.08 , \xi _ { t } = 10 \pm 4 km s ^ { -1 } and v \sin i = 37 \pm 6 km s ^ { -1 } , and the derived abundances indicate a metal-deficient ( [ M/H ] \approx - 0.6 ) post-AGB star .
Chemical abundances of eight different elements were obtained .
The estimates of the CNO abundances in IRAS 18379–1707 indicate that these elements are overabundant with [ ( C+N+O ) /S ] =+0.5 \pm 0.2 suggesting that the products of helium burning have been brought to the surface as a result of third dredge-up on the AGB .
From the absorption lines , we derived heliocentric radial velocity of V _ { \text { r } } = -124.0 \pm 0.4 km s ^ { -1 } .
We have identified permitted emission lines of \ion OI , \ion NI , \ion NaI , \ion SII , \ion SiII , \ion CII , \ion MgII and \ion FeIII .
The nebula forbidden lines of [ \ion NI ] , [ \ion OI ] , [ \ion FeII ] , [ \ion NII ] , [ \ion SII ] , [ \ion NiII ] and [ \ion CrII ] have also been identified .
The Balmer lines H \alpha , H \beta and H \gamma show P-Cygni behaviour clearly indicating post-AGB mass-loss process in the object with the wind velocity up to 170 km s ^ { -1 } .