High-resolution spectroscopy of the high velocity hot post-AGB star IRAS 18379-1707 (LS 5112). (arXiv:1911.12636v1 [astro-ph.SR])

High-resolution spectroscopy of the high velocity hot post-AGB star IRAS 18379-1707 (LS 5112). (arXiv:1911.12636v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Ikonnikova_N/0/1/0/all/0/1">N.P. Ikonnikova</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Parthasarathy_M/0/1/0/all/0/1">M. Parthasarathy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dodin_A/0/1/0/all/0/1">A.V. Dodin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hubrig_S/0/1/0/all/0/1">S. Hubrig</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sarkar_G/0/1/0/all/0/1">G. Sarkar</a>

The high-resolution ($Rsim48,000$) 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 A 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 $T_text{eff}=18~000pm1000$
K, $log g=2.25pm0.08$, $xi_{rm t}=10pm4$ km/s and $v sin i=37pm6$ km/s,
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 $V_text{r}=-124.0pm0.4$ km/s. 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$alpha$, 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.

The high-resolution ($Rsim48,000$) 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 A 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 $T_text{eff}=18~000pm1000$
K, $log g=2.25pm0.08$, $xi_{rm t}=10pm4$ km/s and $v sin i=37pm6$ km/s,
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 $V_text{r}=-124.0pm0.4$ km/s. 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$alpha$, 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.

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