Sm. Andrievsky et al., Magellanic Clouds elemental abundances from F supergiants: Revisited results for the Large Magellanic Cloud, ASTRON ASTR, 367(2), 2001, pp. 605-612
With an improved method of the LTE abundance analysis for most elements (Ko
vtyukh & Andrievsky 1999), the abundances hare been re-investigated in nine
F supergiants of the Large Magellanic Cloud. The NLTE calculations for car
bon, oxygen and sodium, based on Kurucz's atmospheric models with an over-a
ll metal deficiency, were carried out. The most important results are the f
ollowing: - carbon abundance in supergiants is in much better agreement wit
h the carbon abundance of the LMC HII regions, oxygen remaining in fair agr
eement with HII regions. The (C/O) ratio is low, lower than solar and the H
II ratios (a possible sign of the first dredge-up, or another large-scale m
ixing event in the supergiant atmospheres); - the NLTE computations: do not
show remarkable sodium overabundances in the LMC supergiants, in contrast
with the Galactic supergiants; - the mean abundance of iron is found to be
[Fe/H] = -0.40, slightly lower than the results of some previous determinat
ions for the LMC. but in agreement with the recent result obtained bq Kern
ct al. (2000), who give [Fe/H] = -0.41. The relative to iron abundance of o
xygen [O/Fe] = +0.01 derived from nine F supergiants appears to be in excel
lent accordance with predictions based on the smooth model of the LMC evolu
tion; - the (alpha /Fe) ratios are comparable to those found in previous an
alyses. The surprisingly low abundance of Mg is even lower in the new analy
sis, but it is in good agreement with the relative magnesium abundance in L
MC B-stars [Mg/H] = -0.62 determined by Kern et al, (2000). Sulphur in the
program supergiants shows the same abundance within an error bar as in H II
regions; - the iron-group elements follow the solar distribution of the (M
/Fe) ratios; - the heavy elements show enhanced abundances; - significantly
larger log g values were obtained than in a previous study, resulting in s
upergiant masses of about 10-20 M. which are in excellent agreement with ev
olutionary calculations.