Comparison of the H₂O masers around VLA 2 in epoch 2005.89 (left panel; S11) and in epoch 2012.54 (right panel; present work). A comparison of the elliptical fits of the H₂O maser distributions observed in the past 13 years is also shown (see Fig. 1 for more details). The maser LSR radial velocity bar on the right of both panels shows the same velocity range. Four ellipses are drawn, which are assumed to have the same center (the (0, 0) reference position). They are the results of the best fit of the H₂O masers detected by T03 (epoch 1999.25; red dashed ellipse), S11 (epoch 2005.89; green dotted ellipse), K13 (epoch 2007.41; blue dot-dashed ellipse), and the present work (epoch 2012.54; black solid ellipse). Their parameters are listed in Table 1.