Clumpy ultracompact HII regions -- III. Cometary morphologies around   stationary stars
  Cometary ultracompact HII regions have been modelled as the interaction of the hypersonic wind from a moving star with the molecular cloud which surrounds the star. We here show that a similar morphology can ensue even if the star is stationary with respect to the cloud material. We assume that the HII region is within a stellar wind bubble which is strongly mass loaded: the cometary shape results from a gradient in the distribution of mass loading sources. This model circumvents problems associated with the necessarily high spatial velocities of stars in the moving star models. 
R.J.R. Williams(1), J.E. Dyson(1,2) and M.P. Redman(1) ((1) University   of Manchester, (2) University of Leeds)