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We have examined the relationship between the velocity parameters of SiOmasers and the phase of the long period variable stars (LPVs) from which themasers originate. The SiO spectra from the v=1, J=1-0 (43.122 GHz; hereafter$J_{1\rightarrow0}$) and the v=1, J=2-1 (86.2434 GHz; hereafter$J_{2\rightarrow1}$) transitions have been measured using the Mopra Telescopeof the Australia Telescope National Facility. One hundred twenty one sourceshave been observed including 47 LPVs contained in the American Association ofVariable Star Observer Bulletin (2011). The epoch of maxima and the periods ofthe LPVs are well studied. This database of spectra allows for phase dependentcomparisons and analysis not previously possible with such a large number ofsources observed almost simultaneously in the two transitions over a time spanof several years. The velocity centroids ($VCs$) and velocity ranges ofemission ($VRs$) have been determined and compared for the two transitions as afunction of phase. No obvious phase dependence has been determined for the $VC$or $VR$. The results of this analysis are compared with past observations andexisting SiO maser theory.

A Phase Dependent Comparison of the Velocity Parameters of SiO v=1, J=1-0 and J=2-1 Maser Emission in Long Period Variables