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The Origin of the Zanstra Discrepancy: UV Excess in the Central Star Continuum?

Published online by Cambridge University Press:  19 July 2016

R. B. C. Henry  and
H. L. Shipman
R. B. C. Henry
Affiliation:
University of Oklahoma
H. L. Shipman
Affiliation:
University of Oklahoma

Abstract

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The temperature of a planetary nebula central star (CPN) may be determined by observing the nebular flux in an H I or He II recombination line and the stellar flux in a continuum band. The former measures the integrated UV stellar continuum blueward of the ionization edge of the recombined ion. By assuming a continuum shape (usually a blackbody), the ratio of these two fluxes yields an effective temperature for the CPN. This particular method, first introduced by Zanstra (1931), has an advantage over others in that the observables are relatively straightforward to obtain. However, this method also carries a troublesome ambiguity with it: CPN temperatures determined using He II recombination lines. This Zanstra discrepancy is reviewed by Kaler (1985) and Henry and Shipman (1986). Examples of He II and H I temperatures for numerous CPNs are given in Pottasch (1984), where it is shown that the He II Zanstra temperature often exceeds the H I temperature by several times 104K.

Type
III. Central Stars
Information
Symposium - International Astronomical Union , Volume 131: Planetary Nebulae , 1989 , pp. 305
Copyright
Copyright © Kluwer 1989 

References

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Pottasch, S.R. 1984, Planetary Nebulae (Dordrecht: D. Reidel).Google Scholar
Zanstra, H. 1931, Publ. Dom. Ap. Obs. , 4, 209.Google Scholar