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Multivariate Characterization of Hydrogen Balmer Emission in Cataclysmic Variables

Published online by Cambridge University Press:  05 March 2013

Gordon E. Sarty  and
Kinwah Wu
Gordon E. Sarty*
Affiliation:
Departments of Psychology and Physics & Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5A5, Canada Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Surrey RH5 6NT, UK
Kinwah Wu
Affiliation:
Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Surrey RH5 6NT, UK TIARA, Department of Physics, National Tsing Hua University, Hsinchu 300, Taiwan
*
DCorresponding author. E-mail: [email protected]
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Abstract

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The ratios of hydrogen Balmer emission line intensities in cataclysmic variables are signatures of the physical processes that produce them. To quantify those signatures relative to classifications of cataclysmic variable types, we applied the multivariate statistical analysis methods of principal components analysis and discriminant function analysis to the spectroscopic emission data set of Williams (1983). The two analysis methods reveal two different sources of variation in the ratios of the emission lines. The source of variation seen in the principal components analysis was shown to be correlated with the binary orbital period. The source of variation seen in the discriminant function analysis was shown to be correlated with the equivalent width of the Hβ line. Comparison of the data scatterplot with scatterplots of theoretical models shows that Balmer line emission from T CrB systems is consistent with the photoionization of a surrounding nebula. Otherwise, models that we considered do not reproduce the wide range of Balmer decrements, including ‘inverted’ decrements, seen in the data.

Keywords

accretion: accretion discsstars: cataclysmic variablesstars: dwarf novaestars: emission linestars: statistics
Type
Research Article
Information
Publications of the Astronomical Society of Australia , Volume 23 , Issue 3 , 2006 , pp. 106 - 118
Copyright
Copyright © Astronomical Society of Australia 2006

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