Continuum energy distribution of O5 - G0 stars in terms of spectral gradients.

The question of absolute energy distribution of stellar continua is discussed. Available observational material is examined. The relevance of spectral gradients is studied. It is found that the continuum energy distribution from = 0.93 to -i = 3.13 can be very closely represented by spectral gradients, if a proper choice of wave-number bases is made. The influence of interstellar absorption is examined. It is found possible to reduce for this influence by means of a simple reduction formula, provided that MK classfflcations and colour excess values are available. Using intensity values by various authors, gradients are computed and reduced to a common absolute system. The dependence of the correction terms on colour or spectral type are shown to be insiguificant. The intrinsic gradients are studied for each luminosity class, covering a range in spectral type from 0 9 to G 0. A separate study is made of 05-08 stars. Gradient versus spectral type relations are obtained. The dispersion in these relations is found to be explained almost entirely by the statistical errors in the calculated apparent gradients. Thus, the relation between spectral type and intrinsic gradient is a very close one, provided that the material is divided into luminosity classes. Marked differences are found between the various luminosity classes throughout the wave-number interval studied. Also for the 0 stars the dispersion of gradient values is found to be very small. Key wor : energy distribution - continuum - spectral gradients