Massive stars in the Small Magellanic Cloud : Evolution, rotation and surface abundances. (arXiv:2101.09269v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Bouret_J/0/1/0/all/0/1">Jean-Claude Bouret</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Martins_F/0/1/0/all/0/1">Fabrice Martins</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hillier_D/0/1/0/all/0/1">Desmond John Hillier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Marcolino_W/0/1/0/all/0/1">Wagner Marcolino</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rocha_Pinto_H/0/1/0/all/0/1">Helio Rocha-Pinto</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Georgy_C/0/1/0/all/0/1">Cyril Georgy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lanz_T/0/1/0/all/0/1">Thierry Lanz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hubeny_I/0/1/0/all/0/1">Ivan Hubeny</a>
We study the evolutionary and physical properties of evolved O stars in the
Small Magellanic Cloud (SMC), with a special focus on their surface abundances
to investigate the efficiency of rotational mixing as a function of age,
rotation and global metallicity. We analyse the UV + optical spectra of
thirteen SMC O-type giants and supergiants, using the stellar atmosphere code
CMFGEN to derive photospheric and wind properties. We compare the inferred
properties to theoretical predictions from evolution models. For a more
comprehensive analysis, we interpret the results together with those we
obtained for O-type dwarfs in a former study. Most dwarfs lie in the early
phases of the main-sequence. For a given initial mass, giants are further along
the evolutionary tracks, confirming that they are more evolved than dwarfs.
Supergiants have larger initial masses and are located past the terminal age
main-sequence. We find no clear trend of a mass discrepancy, independent of the
diagram used to estimate the evolutionary mass. CNO abundances are consistent
with nucleosynthesis from the CNO cycle. Comparisons to theoretical predictions
reveal the importance of the initial mixture for reproducing the observed
trends in the N/C versus N/O diagram. A trend for stronger chemical evolution
for more evolved objects is observed. More massive stars, are on average, more
chemically enriched at a given evolutionary phase, qualitatively consistent
with evolutionary models. Abundance ratios supports the theoretical prediction
that massive stars at low metallicity are more chemically processed than their
Galactic counterparts. Finally, models including rotation generally reproduce
both the surface abundances and rotation rates, provided different initial
rotational velocities are considered. Nevertheless, there are objects for which
a stronger braking and/or more efficient mixing is required.
We study the evolutionary and physical properties of evolved O stars in the
Small Magellanic Cloud (SMC), with a special focus on their surface abundances
to investigate the efficiency of rotational mixing as a function of age,
rotation and global metallicity. We analyse the UV + optical spectra of
thirteen SMC O-type giants and supergiants, using the stellar atmosphere code
CMFGEN to derive photospheric and wind properties. We compare the inferred
properties to theoretical predictions from evolution models. For a more
comprehensive analysis, we interpret the results together with those we
obtained for O-type dwarfs in a former study. Most dwarfs lie in the early
phases of the main-sequence. For a given initial mass, giants are further along
the evolutionary tracks, confirming that they are more evolved than dwarfs.
Supergiants have larger initial masses and are located past the terminal age
main-sequence. We find no clear trend of a mass discrepancy, independent of the
diagram used to estimate the evolutionary mass. CNO abundances are consistent
with nucleosynthesis from the CNO cycle. Comparisons to theoretical predictions
reveal the importance of the initial mixture for reproducing the observed
trends in the N/C versus N/O diagram. A trend for stronger chemical evolution
for more evolved objects is observed. More massive stars, are on average, more
chemically enriched at a given evolutionary phase, qualitatively consistent
with evolutionary models. Abundance ratios supports the theoretical prediction
that massive stars at low metallicity are more chemically processed than their
Galactic counterparts. Finally, models including rotation generally reproduce
both the surface abundances and rotation rates, provided different initial
rotational velocities are considered. Nevertheless, there are objects for which
a stronger braking and/or more efficient mixing is required.
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