"Convection In Pulsating Stars" by Michael John Robert Costello
 

Physics & Astronomy ETDs

Publication Date

10-27-1977

Abstract

Stellar models using mixing length convection in a linear calculation show a red edge to the instability strip. The models are of a 6 solar mass, 1 x 10 ergs/sec luminos­ity, King 4A composition, cepheid variable star, for various values of effective temperature, Te, and mixing length parameter, a. Results are obtained with an assumed instantaneous adjustment of the convective flux to changes in the local stellar conditions. Calculations of the convective time de­lay show it to be small compared to the period, under the assumption that the convective time delay is due solely to the inertia of convective bubbles. An instability inherent in the mixing length equations is found. The instability is removed by removing the assumption of hydrostatic equilibrium implicit in the usual mixing length equations and by making the mixing length proportional to the equilibrium pressure scale height, P/pg.

Results show the first overtone mode blue and red edges occur at higher Te than the corresponding fundamental mode edges, a1nd that in the center of the strip there is a region where both fundamental and first overtone modes are unstable to pulsation. The calculated blue edge is about 300 K lower than the Sandage and Tammann edge while the calculated red edge depends upon a, but for a= 2.0 falls inside the Sandage and Tammann strip.

Degree Name

Physics

Level of Degree

Doctoral

Department Name

Physics & Astronomy

First Committee Member (Chair)

David Solomon King

Second Committee Member

Arthur N. Cox

Third Committee Member

James Daniel Finley III

Fourth Committee Member

Christopher Pratt Leavitt

Fifth Committee Member

Howard Carnes Bryant

Language

English

Document Type

Dissertation

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