Abundance anomalies in main sequence A stars *
III. Nitrogen and sulphur
Received 28 March 1996 / Accepted 3 May 1996
Nitrogen and sulphur abundances in 15 sharp-lined `normal' main sequence A stars are determined from new high-resolution CCD spectra. Non-LTE effects are taken into account.
Nitrogen abundances are distributed over an interval of 0.5 dex around the solar value of 8.05. Non-LTE abundance corrections range from -0.2 to -1.2 dex.
Sulphur is overabundant with respect to the sun by 0.1 to 0.6 dex in all program stars. Taking non-LTE effects into account reduces the overabundances, but cannot remove them entirely; non-LTE abundance corrections are typically -0.1 dex.
Comparison with previously derived carbon abundances reveals that carbon and nitrogen behave very similarly in each star. Thus the anticorrelation of [C/Si] with [Si/H] found by Holweger (1992) is also true for [N/Si]. For sulphur a similar anticorrelation is also possible.
Key words: stars: abundances stars: early-type stars: individual: Sirius
© European Southern Observatory (ESO) 1997