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NGC 6863



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Characterization of open cluster remnants
Context: Despite progress in the theoretical knowledge of open clusterremnants and the growing search for observational identifications inrecent years, open questions still remain. The methods used to analyzeopen cluster remnants and criteria to define them as physical systemsare not homogeneous. In this work we present a systematic method forstudying these objects that provides a view of their properties andallows their characterization. Aims: Eighteen remnant candidates areanalyzed by means of photometric and proper motion data. These dataprovide information on objects and their fields. We establish criteriafor characterizing open cluster remnants, taking observationaluncertainties into account. Methods: 2MASS J and H photometry isemployed (i) to study structural properties of the objects by means ofradial stellar density profiles, (ii) to test for any similarity betweenobjects and fields with a statistical comparison method applied to thedistributions of stars in the CMDs, and (iii) to obtain ages, reddeningvalues, and distances from the CMD, taking an index of isochrone fitinto account. The UCAC2 proper motions allowed an objective comparisonbetween objects and large solid angle offset fields. Results: Theobjective analysis based on the present methods indicates 13open-cluster remnants in the sample. Evidence of the presence of binarystars is found, as expected for dynamically evolved systems. Finally, weinfer possible evolutionary stages among remnants from the structure,proper motion, and CMD distributions. The low stellar statistics forindividual objects is overcome by means of the construction of compositeproper motion and CMD diagrams. The distributions of remnants in thecomposite diagrams resemble the single-star and unresolved binary stardistributions of open clusters.

Dissolving star cluster candidates
We present a list of 34 neglected entries from star cluster catalogueslocated at relatively high galactic latitudes (|b| >15deg) which appear to be candidate late stages of starcluster dynamical evolution. Although underpopulated with respect tousual open clusters, they still present a high number density contrastas compared to the galactic field. This was verified by means of (i)predicted model counts from different galactic subsystems in the samedirection, and (ii) Guide Star Catalog equal solid angle counts for theobject and surrounding fields. This suggests that the objects arephysical systems, possibly star clusters in the process of disruption ortheir fossil remains. The sample will be useful for followup studies inview of verifying their physical nature.

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Observation and Astrometry data

Right ascension:20h05m07.00s
Apparent magnitude:99.9

Catalogs and designations:
Proper Names   (Edit)
NGC 2000.0NGC 6863

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