NGC 6994: an open cluster which is not an open cluster

Abstract

We report on CCD photometry in the Johnson B,V and I passbands for 146 stars in a 9' \times 9' region around the southern aggregate NGC 6994 (C 2056-128), which appears in the Lynga (1987) catalogue of open star clusters. We argue that this object is not really an open cluster, but simply a random enhancement of four bright stars above the background level. This stars sample includes HD 358033 and GSC 05778-0082, together with M 73, which is referred to as a binary star, but actually represents the whole asterism. Since NGC 6994 is not the first case (see for instance Carraro and Patat 1995), this raises the possibility that other open clusters may have been misclassified. We also suggest that NGC 6994 is unlikely to be an open cluster remnant (OCR).