Central star temperatures of low-excitation planetary nebulae

James B. Kaler, George H. Jacoby

Research output: Contribution to journalArticlepeer-review

Abstract

We correlate Kaler's Stoy (energy balance) and new Zanstra temperatures of the central stars of lowexcitation planetary nebulae with the intensity of [O III] λ5007, where all objects are small (young) and have no or weak He II λ4686 (intensity < 10). More recent energy balance temperatures are shown to be unsatisfactory for this class of objects. We find Ts = 25,840 + 19.30I(λ5007) + 2.8229 × 10-2 I2(λ5007)-1.46115 × 10-5I3(λ5007), Tz(H) = 30,370 + 14.26I(λ5007), and Tz. = 28,380 + 26.13I(λ5007), where for the last we substitute Tz(He II) for Tz(H) in cases where He II is detected. Comparisons among the temperatures show that planetaries may start becoming optically thin for central star temperatures in the 40,000 K-50,000 K range and that the Zanstra discrepancy for this class of objects may be resolved by invoking low optical depth; an excess in the stellar He+ Lyman continuum may also provide a contribution. The Stoy calibration seems to give the best estimate of central star temperatures from the λ5007 line. The correlations are valuable for determining effective temperatures in cases where no nuclei can be detected and are especially useful for extragalactic objects.

Original languageEnglish (US)
Pages (from-to)215-224
Number of pages10
JournalAstrophysical Journal
Volume372
Issue number1
DOIs
StatePublished - May 1 1991

Keywords

  • Nebulae: planetary
  • Stars: early-type

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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