Results of the proper-motion measurements. The large panel shows a scatter plot of the best-fit positions (delta x vs. delta y). Here, each color identifies the best-fit positions from 2004. Black arrows show best-fit directions of the proper motions. The small panel that is placed close to the large one shows a plot of the best-fit positions as a function of time (delta x, y vs. time). Solid lines show the best-fit linear models for the estimations of the mean shift values summarized in Table 3. The error bars show a 68% confidence level, which includes the systematic errors of (σ_x, σ_y) = (0.″5, 0.″5). The fitting (statistical) errors are much smaller than the systematic uncertainties.