2003NewA....8..719C

We have found that six sources listed in the new carbon star catalog are not really carbon-rich objects but oxygen-rich stars, because they all have prominent silicate features in emission at 10 and 18 mum. Moreover, one of them has a typical oxygen-rich spectrum in the optical region, whereas others have SiO maser emission. Most of these objects were considered as carbon stars in the catalog based only on their locations in the near infrared–IRAS two color diagram. Therefore, to use this diagram to distinguish carbon-rich stars from oxygen-rich stars requires caution. For individual star the other methods should be also employed to verify the results from the infrared two color method.