Correlation of Mira's SiO maser properties

The v = 0, 1, and 2, J = 1-0 SiO maser spectra of Mira have been observed with high phase resolution over approximately three periods of the star. A time lag cross-correlation analysis of the integrated flux density and the velocity centroid of the emission indicates that the velocity structure varies in a consistent manner with emission during some oscillation periods of the star. Over two periods of the star the v = 1 integrated flux density and velocity centroid were correlated at the 0.67 level. The velocity centroid reached a maximum 0.066 phase earlier than the integrated flux density. These quantities were anticorrelated at the 0.71 level, with the velocity centroid reaching a minimum 0.59 phase earlier than the integrated flux density maximum. The other maser transitions show lower levels of correlation and other phase relationships. The velocity centroids of the spectra have been analyzed and compared with theoretical predictions of shock passage effects. These observations are relevant for kinematic models of the maser region and for maser-pumping models.