Abstract
Strömgren four-color photometric measures have been made of blue horizontal-branch A stars in the globular clusters M 4, M 13 and M 55 with the Steward Observatory 90 inch telescope and with the 60 inch telescope at Cerro Tololo Inter-American Observatory. These stars are faint, ranging in V magnitude from 13.6 in M 4 to 15.5 in M 13 and the corresponding errors in the four-color indices are ± 0.04 to 0.06 in the c1 index, for one observation. The error of the mean value of the c1 indices is approximately ± 0.02 for most of the stars since they have been measured from 4 to 10 times each.
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© 1988 IAU
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Davis Philip, A.G. (1988). Four-Color Measures of BHB Stars in M 4, M 13 and M 55. In: Grindlay, J.E., Davis Philip, A.G. (eds) The Harlow-Shapley Symposium on Globular Cluster Systems in Galaxies. International Astronomical Union / Union Astronomique Internationale, vol 126. Springer, Dordrecht. https://doi.org/10.1007/978-94-015-1104-9_86
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DOI: https://doi.org/10.1007/978-94-015-1104-9_86
Publisher Name: Springer, Dordrecht
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