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White Dwarf Candidates in the Globular Cluster NGC 6752

Published online by Cambridge University Press:  14 August 2015

Harvey B. Richer*
Affiliation:
Department of Geophysics and Astronomy, University of British Columbia, Vancouver, Canada

Extract

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Recently (Richer 1978, hereafter Paper I), the results of a search for faint blue objects in and around the globular cluster NGC 6752 were reported. The aim of the program was to isolate a sample of white dwarf candidates in this cluster which could then be studied in further detail. The statistics of this survey are as follows: (1) 68 objects found with B ≤ 22.7 and (U-B) ≤ −0.4 within 20 arcmin of the cluster center; (2) of the 68, 36 also had a measurable V magnitude; (3) of these 36, only 11 lay in the area of the color-color diagram occupied by white dwarfs, while the remaining 25 were generally well above the black body line and are probably QSOs or peculiar blue stellar objects; (4) of these 11, 7 are within 14 arcmin of the cluster center and hence have a probability of greater than 50% of being cluster members (King et al. 1968); (5) CTIO 4-m SIT vidicon spectra were obtained of 5 of these 7 candidates, 4 of which appear to be white dwarfs and 1 of which is a QSO with Z = 2. Table 1 lists the derived properties of the 4 white dwarfs assuming that they belong to NGC 6752. The star names are from Paper 1.

Type
August 30 Globular Clusters
Copyright
Copyright © Reidel 1980 

References

Greenstein, J.L., and Sargent, A.I.: 1974, Astrophys. J. Suppl. 28, 157.CrossRefGoogle Scholar
King, I.R., Hedemann, E., and Hodge, S.M.: 1968, Astron. J. 73, 456.Google Scholar
Richer, H.B.: 1978, Astrophys. J. (Letters) 224, L9.Google Scholar
Richer, H.B.: 1979, in Van Horn, H.M. and Weidemann, V. (eds.). Proc. of IAU Colloquim 53: White Dwarfs and Variable Degenerate Stars (in press).Google Scholar