Proper Motions in CW Tau

Top: Proper motion measurements of HH 220. The tangential radial velocity listed assumes a distance of 140 pc to CW Tau. Bottom: Historical V-magnitudes of CW Tau. The range of dates for the ejection of HH 220 are shown. The data prior to 1984 were found using a website described by Herbst et al (1994); filled squares denote points from Rydgren et al. (1984), who collected values from previous sources, and filled circles are from Walker (1987). Data from Bouvier et al (1995, open circles) and Oudmaijer et al (2001, triangles) also appear in the plot. Although CW Tau was somewhat brighter than average during the period of ejection, the difference is not striking