SIMBAD references

We present the results of a kinematical study of the W 50 nebula using high-resolution radio observations from the Very Large Array spanning a 12-yr period, sampled in 1984, 1993 and 1996. We conduct a careful analysis of the proper motions of the radio filaments across the W 50 nebula at each epoch and detect no significant motion for them during this period. The apparent lack of movement in the radio filaments mandates either (i) a high degree of deceleration of SS 433's jet ejecta in the W 50 nebula; or (ii) that the lobes of W 50 formed a long time ago in SS 433's history, during a jet outburst with appreciably different characteristics from the well-known precessing jet state observed in SS 433 at the present day. We discuss the possible scenarios which could explain this result, with relevance to the nature of SS 433's current jet activity.