Magnetic Intensification of Stellar Absorption Lines.

The total intensity of a saturated absorption line may be increased several fold in a magnetic field of a few kilogauss because the Zeeman pattern may be considerably wider than the thermal Doppler profile. The effect should be particularly marked for lines having wide, anomalous Zeeman patterns of many components; it is enhanced for elements of high atomic weight at reduced temperatures and in the ab- sence of turbulence. An upper limit to the intensification factor is half the number of components in the Zeeman pattern of the line. A method is developed for computing the magnetic intensification, W~/W0, for a saturated line of given pattern in integrated light of a star viewed from the direction of the pole (i = 00) or viewed from the plane of the star's equator (~ = 90°). For the line Fe i X 4260, having a triplet pattern (Z = 1.60), W~/Wo = 1.25 for a field of 8 kilogauss and a temperature of 10,000°. The intensification factor appears to be essentially independent of i; it may approach 7 for an exceptional line like Eu ii X 4205, which has 21 widespread components. If equivalent widths can be measured, it should be possible in principle to estimate stellar magnetic field strengths by detailed comparisons of lines se]ectively intensified by Zeeman splitting, even if pronounced rotational broadening is present. In a number of the peculiar stars of type A, magnetic fields ranging up to several kilogauss have been measured with the polarizing analyzer; the conclusion is practically inescapable that magnetic intensifica- tion must contribute to the abnormal line intensities in the spectra of some of these stars. For about fifty lines in the spectrum of a2 CVn, for which intensity estimates at three phases of the spectral variation have been published by Struve and Swings, the degree of observed intensity variation is compared with the magnetic intensification factor predicted from the Zeeman patterns; a satisfactory correspondence is found. I. INTRODUCTIO