  We present an analysis of velocity parameters derived from multi-epoch
observations of the SiO maser spectra of 47 long period variables (LPVs). The
velocity parameters are important to inform and constrain theoretical models of
SiO maser emission and to extract information on binary orbits. Mira and R
Aquarii (R Aqr) are two known binaries included in the program. The 47 LPVs are
among 121 sources of the Australia Telescope National Facility (ATNF) Mopra
telescope's monitoring program. Observations were carried out several times a
year between 2008 and 2012 and are continuing. The SiO spectra are from the
v=1, J=1-0 (43.122 GHz; hereafter J10) and the v=1, J=2-1 (86.2434 GHz;
hereafter J21) transitions. For 41 of the 47 LPVs we observed both transitions
nearly simultaneously in 457 observations. We have determined and compared the
velocity centroids (VCs) and velocity ranges of emission (VRs) suffixed as
above (10 and 21) for the two transitions - VC10, VC21, VR10, and VR21. The VCs
of the two transitions are, on average, within 0.13 km s-1 of each other but
are sometimes separated by a few km s-1. The VC10s are, on average, slightly
more positive than the VC21s. The values of the VCs in the two transitions have
been compared to justify using both of these transitions to extract binary star
orbital parameters. The arithmetic mean VR10 derived from 635 observations of
47 sources is 6.4 km s-1 with a standard deviation of 3.4 km s-1 while the mean
VR21 derived from 485 observations of 41 sources is 4.2 km s-1 with a standard
deviation of 2.8 km s-1. The number of occurrences of VR10 and VR21versus
velocity range have different distributions. The differences in the VRs
indicate that the J21 and J10 emissions arise from dynamically different
regions of the circumstellar environment.

Solar and Stellar Astrophysics