High-resolution spectroscopy of the high-velocity hot post-AGB star IRAS 18379–1707 (LS 5112). Issue 4 (29th November 2019)

• Record Type: Journal Article
• Authors: Ikonnikova, N P; Parthasarathy, M; Dodin, A V; Hubrig, S; Sarkar, G
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 491:Issue 4(2020)
• Page Start: 4829
• Page End: 4842
• Publication Date: 2019-11-29
• Subjects: stars: abundances -- stars: AGB and post-AGB -- stars: atmospheres -- stars: early-type -- stars: evolution -- stars: individual: IRAS 18379–1707, 62 Ori; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stz3355
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: 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 eff = 18 000 ± 1000 K, log g = 2.25 ± 0.08, ξt = 10 ± 4 km s −1, and v sin i = 37 ± 6 km s −1, and the derived abundances indicate a metal-deficient ([M/H] ≈ −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 ± 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 r = −124.0 ± 0.4 km s −1 . We have identified permitted emission lines of O i, N i, Na i, S ii, Si ii, C ii, Mg ii, and Fe iii . The nebula forbidden lines of [N i ], [O i ], [Fe ii ], [N ii ], [S ii ], [Ni ii ], and [Cr ii ] have also been identified. The Balmer lines H α, H β, and H γ show P-Cygni behaviour clearly indicating post-AGB mass-loss process in the object with the wind velocity up to 170 km s −1 .