Investigation of Galactic open cluster remnants: the case of NGC\,7193

M. ANGELO + 3 COAUTHORS; A.E. PIATTI

RESEARCH IN ASTRONOMY AND ASTROPHYSICS

NATL ASTRONOMICAL OBSERVATORIES

Lugar: Beijing; Año: 2017 vol. 17 p. 1 - 24

1674-4527

Galactic open clusters (OCs) that survive the early gas-expulsion phase are grad-ually destroyed over time by the action of disruptive dynamical processes. Their final evo-lutionary stages are characterized by a poorly populated concentration of stars called opencluster remnant (OCR). This study is devoted to assess the real physical nature of the OCRcandidate NGC 7193. GMOS/Gemini spectroscopy of 53 stars in the inner target region wereobtained to derive radial velocities and atmospheric parameters. We also employed photomet-ric and proper motion data. The analysis method consists of the following steps: (i) analysisof the statistical resemblance between the cluster and a set of field samples with respect tothe sequences defined in colour-magnitude diagrams (CMDs); (ii) a 5-dimensional iteractiveexclusion routine was employed to identify outliers from kinematical and positional data;(iii) isochrone fitting to the K s × (J − K s ) CMD of the remaining stars and the dispersion of123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960Research in Astronomy and Astrophysicsspectral types along empirical sequences in the (J − H) × (H − K s ) diagram was checked. Agroup of stars was identified for which the mean heliocentric distance is compatible with thatobtained via isochrone fitting and whose metallicities are compatible with each other. Fifteenmember stars observed spectroscopically were identified together with other 19 probablemembers. Our results indicate that NGC 7193 is a genuine OCR, of an once very populousOC, for which the following parameters were derived: d = 501 ± 46 pc, t = 2.5 ± 1.2 Gyr,[F e/H]= −0.17 ± 0.23 and E(B − V ) = 0.10 ± 0.05 E(B − V ) = 0.05 ± 0.05.Its luminosity and mass functions show depletion of low mass stars, confirming the OCRdynamically evolved state.