Automated star counts in the southern globular cluster NGC 6809 (M55)

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view Abstract Citations (69) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Automated star counts in the southern globular cluster NGC 6809 (M55). Irwin, M. J. ; Trimble, V. Abstract The authors report star counts, as a function of position and apparent magnitude, in the rich, relatively open southern globular cluster NGC 6809 (M55). Three AAO 150arcsec plates were scanned by the Automatic Plate Measuring System (APM) at the Institute of Astronomy, Cambridge, and 20825 images were counted by its associated software. Previously known features of rich globular clusters which appear in the raw counts include a flattening of the luminosity function below MB ≡ +5.2, increased central concentration of bright stars relative to faint ones (normally interpreted as mass segregation), and mild deviations in radial profile from King models. Crowding of the field, which causes the counting procedure to miss faint stars preferentially near the cluster center, contributes to all of these, and may be responsible for all of the apparent mass segregation, but not for all of the other two effects. Publication: The Astronomical Journal Pub Date: January 1984 DOI: 10.1086/113485 Bibcode: 1984AJ.....89...83I Keywords: Astronomical Photography; Globular Clusters; Image Analysis; Star Distribution; Stellar Luminosity; Astronomical Coordinates; Image Processing; Mass To Light Ratios; Photographic Measurement; Stellar Magnitude; Variable Stars; Astronomy; Globular Clusters:Luminosity Function; Globular Clusters:Star Counts; Luminosity Function:Globular Clusters; Star Counts:Globular Clusters full text sources ADS | data products SIMBAD (6)