1997A&A...319..244U

We present a uniform and high quality set of infrared photometric (JHK) observations of the 6 peculiar carbon giant stars V Ari, UV Cam, BD+34 911, TU Gem, BD+57 2161 and BD+34 4134. All of these belong to the small group of known cool CH giants populating the Galactic halo. Comparison of the J-H and H-K colours to "normal" C stars show our stars to be "bluer" (i.e., having lower values of J-H and H-K) than the bulk of the Galactic C stars. Comparison with synthetic JHK colours reveal 5 of our 6 stars as having considerably lower metallicities and/or higher temperatures than the bulk. Using standard assumptions we derive estimates of their effective temperatures, gravities, luminosities and distances. Their derived luminosities place them close to (or below) the theoretical first He shell flash luminosity, although other observations indicate their carbon excess to be intrinsic.