We present proper motions of water masers toward the Onsala 1 star forming region , observed with the Japanese VLBI network at three epochs spanning 290 days .
We found that there are two water maser clusters ( WMC1 and WMC2 ) separated from each other by \timeform 1 ” .6 ( 2900 AU at a distance of 1.8 kpc ) .
The proper motion measurement reveals that WMC1 is associated with a bipolar outflow elongated in the east-west direction with an expansion velocity of 69 \pm 11 km s ^ { -1 } .
WMC1 and WMC2 are associated with two 345 GHz continuum dust emission sources , and located \timeform 2 ” ( 3600 AU ) east from the core of an ultracompact H \emissiontype II region traced by 8.4 GHz radio continuum emission .
This indicates that star formation activity of Onsala 1 could move from the west side of ultracompact H \emissiontype II region to the east side of two young stellar objects associated with the water masers .
We also find that WMC1 and UC H \emissiontype II region could be gravitationally bound .
Their relative velocity along the line of sight is \sim 3 km s ^ { -1 } , and total mass is \sim 37 \MO .
Onsala 1 seems to harbor a binary star at different evolutionary stage .