Very Large Array Observations of Proper Motions in L1551 IRS 5

Using high angular resolution (~0 1) Very Large Array observations made at 2 cm during the period 1983 to 1998, we report the detection of proper motions in the components of the binary radio source in L1551 IRS 5. The absolute proper motions observed in these two protostars, of order 25 mas yr -1 or ~17 km s -1 at a distance of 140 pc, are very similar in magnitude and direction to those of T Tauri stars in the same region and are attributed to the large-scale motion of the parent molecular complex. The relative astrometry between the two components reveals orbital proper motions that suggest that the total mass and period of the binary system are ~1.2 M ☉ and ~260 yr, respectively.