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The Effects of Metal Enhancement on the Period Ratio of Double Mode Cepheids

Published online by Cambridge University Press:  12 April 2016

Siobahn Morgan  and
Arthur N. Cox
Siobahn Morgan
Affiliation:
University of Washington, Seattle WA, USA
Arthur N. Cox
Affiliation:
Los Alamos National Laboratory, Los Alamos NM, USA

Abstract

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We increase the metal abundance in the envelope of Double Mode Cepheids (DMCs) in order to remove the period ratio mass discrepancy. By increasing the value of Z, we are able to increase the opacity by a factor of 2 to 2.5. We find that for a star of 5 solar masses, with a temperature of 5957 K, and a luminosity of 1050 times that of the sun, an increase in the metal abundance starting at the Log (T) value of 4.79 and reaching a maximum Z value of 0.3 in the Log (T) range of 4.8 to 5.3 produces a period ratio P1/P0 = 0.7089, and a value of P0 = 3.001 days. The value of Z returns to 0.02 at Log (T) = 5.62. The enhanced zone (part of which convects) is located well below the H and He convective regions. The enhanced region is also stable against downward mixing since the radiative gradient is so sub-adiabatic.

Type
4. Abstracts of Poster Papers
Information
International Astronomical Union Colloquium , Volume 111: The Use of Pulsating Stars in Fundamental Problems of Astronomy , 1989 , pp. 278
Copyright
Copyright © Cambridge University Press 1989