2005ApJ...627L..45B

We present observational evidence that the OH/IR star OH 12.8-0.9 is the fourth in a class of objects previously dubbed ``water-fountain'' sources. Using the Very Long Baseline Array, we produced the first images of the H₂O maser emission associated with OH 12.8-0.9. We find that the masers are located in two compact regions with an angular separation of ∼109 mas on the sky. The axis of separation between the two maser regions is at a position angle of 1°.5 east of north, with the blueshifted (-80.5 to -85.5 km/s) masers located to the north and the redshifted (-32.0 to -35.5 km/s) masers to the south. In addition, we find that the blue- and redshifted masers are distributed along arclike structures ∼10-12 mas across, oriented roughly perpendicular to the separation axis. The morphology exhibited by the H₂O masers is suggestive of an axisymmetric wind with the masers tracing bow shocks formed as the wind impacts the ambient medium. This bipolar jet-like structure is typical of the three other confirmed water-fountain sources. When combined with the previously observed spectral characteristics of OH 12.8-0.9, the observed spatiokinematic structure of the H₂O masers provides strong evidence that OH 12.8-0.9 is indeed a member of the water-fountain class.