The NLTE Analyses of Carbon Emission Lines in the Atmospheres of O and B type Stars. (arXiv:1909.07702v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Alexeeva_S/0/1/0/all/0/1">Sofya Alexeeva</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sadakane_K/0/1/0/all/0/1">Kozo Sadakane</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nishimura_M/0/1/0/all/0/1">Masayoshi Nishimura</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Du_J/0/1/0/all/0/1">Junju Du</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hu_S/0/1/0/all/0/1">Shaoming Hu</a>
We present a model atom for C I – C II – C III – C IV using the most
up-to-date atomic data and evaluated the non-local thermodynamic equilibrium
(NLTE) line formation in classical 1D atmospheric models of O-B-type stars. Our
models predict the emission lines of C II 9903~AA and 18535~AA to appear at
effective temperature Teff~$geq$~17,500~K, those of C II 6151~AA and
6461~AA to appear at Teff~$>$~25,000~K, and those of C III 5695, 6728–44,
9701–17~AA to appear at Teff~$geq$~35,000~K (log~$g$=4.0). Emission
occurs in the lines of minority species, where the
photoionization-recombination mechanism provides a depopulation of the lower
levels to a greater extent than the upper levels. For C II 9903 and 18535~AA,
the upper levels are mainly populated from C III reservoir through the Rydberg
states. For C III 5695 and 6728–44~AA, the lower levels are depopulated due
to photon losses in UV transitions at 885, 1308, and 1426–28~AA which become
optically thin in the photosphere. We analysed the lines of C I, C II, C III,
and C IV for twenty-two O-B-type stars with temperature range between 15,800
$leq$~Teff~$leq$ 38,000~K. Abundances from emission lines of C I, C II and
C III are in agreement with those from absorption ones for most of the stars.
We obtained log~$epsilon_{rm C}$=8.36$pm$0.08 from twenty B-type stars, that
is in line with the present-day Cosmic Abundance Standard. The obtained carbon
abundances in 15~Mon and HD~42088 from emission and absorption lines are
8.27$pm$0.11 and 8.31$pm$0.11, respectively.
We present a model atom for C I – C II – C III – C IV using the most
up-to-date atomic data and evaluated the non-local thermodynamic equilibrium
(NLTE) line formation in classical 1D atmospheric models of O-B-type stars. Our
models predict the emission lines of C II 9903~AA and 18535~AA to appear at
effective temperature Teff~$geq$~17,500~K, those of C II 6151~AA and
6461~AA to appear at Teff~$>$~25,000~K, and those of C III 5695, 6728–44,
9701–17~AA to appear at Teff~$geq$~35,000~K (log~$g$=4.0). Emission
occurs in the lines of minority species, where the
photoionization-recombination mechanism provides a depopulation of the lower
levels to a greater extent than the upper levels. For C II 9903 and 18535~AA,
the upper levels are mainly populated from C III reservoir through the Rydberg
states. For C III 5695 and 6728–44~AA, the lower levels are depopulated due
to photon losses in UV transitions at 885, 1308, and 1426–28~AA which become
optically thin in the photosphere. We analysed the lines of C I, C II, C III,
and C IV for twenty-two O-B-type stars with temperature range between 15,800
$leq$~Teff~$leq$ 38,000~K. Abundances from emission lines of C I, C II and
C III are in agreement with those from absorption ones for most of the stars.
We obtained log~$epsilon_{rm C}$=8.36$pm$0.08 from twenty B-type stars, that
is in line with the present-day Cosmic Abundance Standard. The obtained carbon
abundances in 15~Mon and HD~42088 from emission and absorption lines are
8.27$pm$0.11 and 8.31$pm$0.11, respectively.
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