The nitrogen abundance in the atmospheres of single and binary stars.

The nitrogen abundances for 47 single, 11 visual double, and 41 close binary stars are obtained from high-dispersion W_lambda determinations of nitrogen lines using atmospheric models and theoretical calculations of N II lines, taking LTE errors into account. The mean value of lg N(N) is found to be 8.05 for single stars, 8.50 for close binaries, and 8.15 for visual double stars. A correlation is found between the nitrogen abundance and the helium and carbon abundances. It is suggested that considerable mixing between the central part of stars and the atmosphere occurs in binary stars.