Chandra, Subhash (1966) A study of spectroscopic and kinematic characteristics of peculiar A-type stars. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-05012008-090141
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A spectroscopic survey of the different types of peculiar-A (Ap) stars has been made to discover the systematics of behavior of the various elements. Spectroscopic results are preceded by an account of some of the "gross Properties" investigated from the published data.
Gross Properties: (Chapter II): Under this group of investigations (a) intrinsic frequency distribution of the various peculiarity types is derived, (b) the controversy "whether Ap stars are too blue for their HD spectral types" is resolved, (c) mean absolute magnitudes of the different peculiarity types are derived by a statistical analysis of trigonometric parallaxes, and (d) space velocities are calculated which show significantly different solar motions for the different groups, but the velocity dispersions are found to be comparable.
Spectroscopic Studies: This study is based mainly on 21 to 45 (A/mm) dispersion plates, in the UV and blue regions of the spectrum of [...] Ap and [...] normal stars. k (A) (Chapter III) By eliminating the effects of temperature, electron pressure, continuous absorption and microturbulence, "strengthening" and "weakening" of various elements has been estimated. From these estimates (Chapter VI): (i) behavior of the various elements in Ap stars is described, (ii) several interesting correlations between the observed anomalies of various elements have been discovered, and (iii) for Ap stars, a new system of classification is proposed which is based on the general pattern of abnormalities rather than on single most prominent features. (B) Extensive tables of reliable blend-free UV and blue lines are given for detection of the various elements (Chapter III). A similar table is given for the detection of all the rare-earths (Chapter V). In different stars, relative distribution of the rare-earths is found to be different. (C) A survey of BeII [...]3130-31 is made. In seven Ap stars, from "Mn" and "Si-4200" groups, this doublet is very strong. A quantitative Be abundance analysis is given (Chapter IV).
Various explanations for the appearance of the abnormal line strengths -- including the predicted nuclear processes -- are discussed in the light of the present results. Some specific suggestions for further work are also made (Chapter VI).
|Item Type:||Thesis (Dissertation (Ph.D.))|
|Degree Grantor:||California Institute of Technology|
|Division:||Physics, Mathematics and Astronomy|
|Thesis Availability:||Public (worldwide access)|
|Defense Date:||20 May 1966|
|Default Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Imported from ETD-db|
|Deposited On:||13 May 2008|
|Last Modified:||26 Dec 2012 02:39|
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