Equivalent widths of Hγ in the Magellanic Clouds

Abstract

J. B. Hutchings has measured equivalent widths of Hγin the large stock of Radcliffe spectra of stars in the Magellanic Clouds. The maximum equivalent width occurs at spectral type Fo due to the very low pressures in the atmospheres of these supergiants. Curves relating equivalent width (reduced to types Ao and B3) with apparent magnitude are presented and agree reasonably well with the corresponding galactic calibration of absolute magnitudes. Among the stars of highest luminosity, measured equivalent widths may be affected by both (a) emission, and (b) presence of expanding shells.Hutchings has also detected in some of these spectra the presence of 4430Å absorption originative within both Clouds.