EVOLUTION OF H-ALPHA EMISSION PROFILES IN S-TYPE MIRA STARS

High-dispersion observations of the Ha profile in S-type Mira stars ha ve been obtained at a number of different phases. Because it is diffic ult to obtain wide phase coverage on individual stars (with typical pe riods of around 300 days), observations obtained from a number of diff erent stars were combined and analyzed as if they were all from the sa me star. This procedure yielded quite consistent results. The profiles , considered by previous authors to consists of two components, have b een modeled as the sum of three emission components of equal width, tw o of which are blended. Supplemental H beta and H gamma observations s how a single feature close to the velocity of the middle H alpha emiss ion component. The relative amplitudes of these components, as well as the velocity of the red component, vary smoothly with advancing phase , Although it is uncertain, the three components may correspond to phy sically distinct emitting regions.