ON THE NATURE OF THE STELLAR GROUP ESO442-SC04

MAIA, F.F.S.; SANTOS JR, JOÂO F.C.; CORRADI, W.J.B.; PIATTI, ANDRÉS E.

Passa Quatro (MG, Brazil)

Congreso; Reunion de la Sociedade Astronomica Brasileira; 2008

Sociedade Astronomica Brasileira

As a consequence of the dynamical evolution of open clusters, it is an expected fact theoccurrence of systems characterized by loose clumps with small number of stars in theintermediate state between well defined, concentrated, dense structures and disruptedsystems. According to the present knowledge on how this dynamical evolution occurs,the timescales involved indicate that finding clusters in the state of dissolution shouldbe common. In this context, there is a controversy whether ESO442-SC04 is, in fact, adissolving open cluster or the result of a fortuit alignment of stars. Carraro et al. (2005)based on Color-Magnitude (CMD) and Vector-Point Diagrams (VPD) argued that thestructure is not real. However, based on the surface density of stars and the 2MASSCMD of the central parts we believe that ESO442-SC04 is a Possible Open ClusterRemnant (POCR). We propose a definitive test on its real physical nature. In orderto pursue such analysis, we carried out multi-object spectroscopy of stars in its innerarea using GMOS at Gemini-S telescope. By determining their radial velocity andmetallicity, in conjunction with 2MASS color-magnitude diagrams and proper motionanalyses, we aim at evaluating if the stars form a physical system. Preliminary analysisof the radial velocity data for 8 stars on the central region of the object suggests thatthe stars are not dynamically bound according to the large radial velocity dispersion (30 km/s).