1997A&A...327..758F

An earlier multi-epoch high angular resolution study of the 22GHz H₂O maser emission from the dark cloud core L 1287 presented an unusual position-velocity distribution of the identified masers. Since the observational results could only unsatisfactorily be modeled in terms of an outflow association, the alternative interpretation of a disk origin is investigated in some more detail. Clumpy mass infall onto the accretion disk around the embedded protostar in L 1287 is identified as the hydrodynamic trigger mechanism for the maser excitation. Shock compressed clump layers are found likely to have the required density, temperature and column density for detectable 22GHz H₂O maser emission. A simplified model of the velocity field in the shocked clump layers leads to a remarkable agreement with the position-velocity distribution of the observed masers.