Planetary nebula central stars - A detailed examination of the sensitivity of the Zanstra temperature method to stellar and nebular parameters

Abstract

view Abstract Citations (36) References (40) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Planetary Nebula Central Stars: A Detailed Examination of the Sensitivity of the Zanstra Temperature Method to Stellar and Nebular Parameters Henry, Richard B. C. ; Shipman, Harry L. Abstract Blackbody continua and model stellar atmospheres, representing a large range in Teff, He/H, and log g, were employed in conjunction with photoionization models to assess the validity of the Zanstra method of determining the temperatures of central stars of optically thick planetary nebulae. The blackbody continua were used to establish that, for nebulae for which H-beta and He II emission can be measured to an accuracy of about 80 percent, the UV photon counting capabilities of these lines are not substantially influenced or lowered by radiative transfer effects associated with low values of the ionization parameter. For the model stellar atmospheres tested, the H I Zanstra temperature agreed with the stellar effective temperature to within 10 percent. Thus, for an optically thick nebula, it is a reasonable temperature to use in placing central stars on the HR diagram. However, the He II Zanstra temperature can differ sharply from the H I Zanstra temperature when the atmospheric helium level differs markedly from solar. Furthermore, the sign and magnitude of the observed difference suggests that most central stars which show large Zanstra temperature discrepancies have photospheres with low He/H abundance ratios, significantly lower than solar. Publication: The Astrophysical Journal Pub Date: December 1986 DOI: 10.1086/164815 Bibcode: 1986ApJ...311..774H Keywords: Optical Thickness; Planetary Nebulae; Stellar Evolution; Stellar Temperature; White Dwarf Stars; Black Body Radiation; Continuous Spectra; Emission Spectra; Photoionization; Stellar Atmospheres; Stellar Models; Astrophysics; NEBULAE: PLANETARY; STARS: ATMOSPHERES; STARS: EVOLUTION; STARS: WHITE DWARFS full text sources ADS |