Bump masses for BL Her stars

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The masses of classical Cepheids can be determined by using the phase of the Hertzsprung bump on the light or velocity curve, Cox-Stewart opacities, and nonlinear pulsation theory. The fact that these bump masses are some 60% lower than the evolutionary masses raises some questions about this approach. In support of our method, we calculate the light curve for BL Her, a population II Cepheid, with an observed bump on the declining portion of its light curve. The nonlinear hydrodynamic model we use (Davis and Davison - 1978) resolves the light curve by dynamic zoning and allows us the opportunity ... continued below

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Pages: 6

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Davis, C.G. January 1, 1982.

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Description

The masses of classical Cepheids can be determined by using the phase of the Hertzsprung bump on the light or velocity curve, Cox-Stewart opacities, and nonlinear pulsation theory. The fact that these bump masses are some 60% lower than the evolutionary masses raises some questions about this approach. In support of our method, we calculate the light curve for BL Her, a population II Cepheid, with an observed bump on the declining portion of its light curve. The nonlinear hydrodynamic model we use (Davis and Davison - 1978) resolves the light curve by dynamic zoning and allows us the opportunity to make a direct comparison of the calculated light curve to the observations, using a prescribed mass, luminosity and effective temperature. The parameters for BL Her are from a linear model (Hodson, Cox, and King - 1982) that has nearly the correct period (1./sup d/2) and the correct period ratio from resonance theory (..pi../sub 2//..pi../sub 0/ = 0.53) for a bump to appear on the declining portion of the light curve as observed. These parameters are: M = 0.55 M, L = 95.0 L, and T/sub eff/ = 6500 K. This mass is near the evolutionary mass as described by Schwartzschild and Haerm (1970). The model results agree well with the observations and the color-T/sub eff/ relation has the same slope as that observed for RR Lyrae stars by the Oke, Giver and Searle (1965) relationship.

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Pages: 6

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NTIS, PC A02/MF A01.

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  • Conference on pulsations in classical and cataclysmic variable stars, Boulder, CO, USA, 1 Jun 1982

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  • Other: DE82019564
  • Report No.: LA-UR-82-2008
  • Report No.: CONF-8206101-2
  • Grant Number: W-7405-ENG-36
  • Office of Scientific & Technical Information Report Number: 5100744
  • Archival Resource Key: ark:/67531/metadc1061218

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • January 1, 1982

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  • Jan. 22, 2018, 7:23 a.m.

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  • Feb. 1, 2018, 7:01 p.m.

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Davis, C.G. Bump masses for BL Her stars, article, January 1, 1982; New Mexico. (digital.library.unt.edu/ark:/67531/metadc1061218/: accessed April 22, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.