engleski

CN status of a sample of galactic OB supergiants

In search for evidence for the CNO processed material in the atmospheres of galactic OB supergiants we measured the equivalent widths of photospheric lines in the high-resolution IUE spectra. A sample of 36 stars was investigated and the following lines were studied: He II 1640 Å ; , C III 1247 Å ; , N IV 1718 Å ; , O IV 1339 Å ; , Si III 1299 Å ; , Fe IV 1682 Å ; , Fe IV 1688 Å ; , Fe IV 1765Å ; . All ions show a well-defined dependence on effective temperature. Comparison of stars with questionable CN status with normal stars gives evidence for decrease in equivalent widths of C III and O IV lines accompanied by increase in equivalent widths of N IV and He II lines, which leads to abundance differences. The CN status has been compared with results obtained in the visual.

supergiants; atmospheres; abundances; UV spectroscopy

nije evidentirano