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White Dwarf Candidates in the Globular Cluster NGC 6752

Published online by Cambridge University Press:  12 April 2016

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

Extract

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In a recent paper (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 plate material for this survey consisted of a set of deep UBV plates (only one in each color) obtained at the prime focus of the Cerro Tololo Interamerican Observatory 4-meter telescope. Limiting magnitudes reached by the plates were about U=22.4, B=23.0, V=22.0. A reanalysis of the photometry presented in Paper I (using a reduction program supplied by W. Harris [see Stetson and Harris 1977]) has now yielded a total of 68 candidate objects within 20′ of the cluster center having B≤22.7 and (U–B) ≤ –0.4. Although the accuracy of the photometry is low (about ±0.2 magnitudes), it seems clear that the preponderance of the objects do not have UBV colors typical of white dwarfs. Of the 68 candidate objects, 36 had a measurable V magnitude, and only 11 of these lay in the area of the color-color diagram known to be occupied by white dwarfs (Eggen and Greenstein 1965). The remaining 25 were generally well above the black body line in the two-color diagram and are probably QSO’s or peculiar blue stellar objects. Among these 11 good candidates, 7 are within 14’ of the cluster center and hence have a probability of greater than 50% of being cluster members according to the star counts of King et al (1968) assuming that white dwarfs have a radial distribution in NGC 6752 similar to other cluster members.

Type
Colloquium Session IV
Information
International Astronomical Union Colloquium , Volume 53: White Dwarfs and Variable Degenerate Stars , August 1979 , pp. 259 - 265
Copyright
Copyright © The University of Rochester 1979

References

Arp, H.C. 1965, in Galactic Structure, eds. Blaauw, A. and Schmidt, M. (Chicago: University of Chicago Press), chap. 19.Google Scholar
Cannon, R.D., and Stobie, R.S. 1973, M.N.R.A.S., 162, 227.CrossRefGoogle Scholar
Carney, B.W. 1979, A.J., 84, 515.Google Scholar
Eggen, O.J., and Greenstein, J.L. 1965, Ap.J., 141, 83.Google Scholar
Greenstein, J.L. 1960, in Stellar Atmospheres, ed. Greenstein, J.L. (Chicago: University of Chicago Press), chap. 19.Google Scholar
Greenstein, J.L., and Sargent, A.I. 1974, Ap.J.Suppl., 28, 157.Google Scholar
Hills, J.G. 1974, Ap.J., 190, 109.Google Scholar
King, I.R., Hedemann, E., and Hodge, S.M. 1968, A.J., 73, 456.CrossRefGoogle Scholar
Oke, J.B. 1974, Ap.J.Suppl., No. 235, 27, 21.Google Scholar
Richer, H.B. 1978, Ap.J. (Letters), 224, L9.Google Scholar
Shipman, H.L. 1972, Ap.J., 177, 723.Google Scholar
Stetson, P.B., and Harris, W.E. 1977, A.J., 82, 954.Google Scholar
Trimble, V., and Greenstein, J.L. 1972, Ap.J., 177, 441.CrossRefGoogle Scholar
Weidemann, V. 1968, Ann. Rev. Astr. and Ap., 6, 351.CrossRefGoogle Scholar
Wesselink, A.J. 1974, M.N.R.A.S., 168, 345.Google Scholar