The APM Survey for cool carbon stars in the Galactic halo - II. The searchfor dwarf carbon stars

We present proper-motion measurements for carbon stars found during the APM Survey for Cool Carbon Stars in the Galactic halo as reported in an earlie r paper by Totten & Irwin. Measurements are obtained using a combination of POSSI, POSSII and UKST survey plates supplemented where necessary by CCD f rames taken at the Isaac Newton Telescope. We find no significant proper mo tion for any of the new APM colour-selected carbon stars and so conclude th at there are no dwarf carbon stars present within this sample. We also pres ent proper-motion measurements for three previously known dwarf carbon star s and demonstrate that these measurements agree favourably with those previ ously quoted in the literature, verifying our method of determining proper motions. Results from a complimentary program of JHK photometry obtained at the South African Astronomical Observatory are also presented. Dwarf carbo n stars are believed to have anomalous near-infrared colours, and this feat ure is used for further investigation of the nature of the APM carbon stars . Our results support the use of JHK photometry as a dwarf/giant discrimina tor and also reinforce the conclusion that none of the new APM-selected car bon stars is a dwarf. Finally, proper-motion measurements combined with ext ant JHK photometry are presented for a sample of previously known halo carb on stars, suggesting that one of these stars, CLS29, is likely to be a prev iously unrecognized dwarf carbon star.