NOAO >   Observing Info >   Approved Programs >   2002B-0023

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Proposal Information for 2002B-0023


PI: Edward G. Schmidt, Universtiy of Nebraska-Lincoln, eschmidt1@unl.edu
Address: Lincoln, NE 68588-0111, USA

CoI: Kevin M. Lee, University of Nebraska-Lincoln

Title: The Pulsational Properties of Type II Cepheid Variable Stars

Abstract: We have undertaken a photometric study of the pulsational properties of Population II or Type II Cepheid variable stars. Although in principle the Type II Cepheids are a well defined group, distinguishing between Type II Cepheids and the more numerous Classical Cepheids on the basis of easily observed properties is often ambiguous and can not be trusted in many cases. There are also significant differences among the properties of individual Type II Cepheids which confuse classification and need to be understood to relate them to theory. To provide a firm basis for the investigation of the pulsation, we are approaching the classification of Cepheids in a new way. We will assemble a database of parameters for each of about 50 presumed Type II Cepheids and 20 Classical Cepheids. Cluster analysis will then be used to find groups of stars which can be associated with Type II and Classical Cepheids and perhaps with subgroups among the Type II stars. Many of the parameters will come from photometry done at Behlen Observatory (such as Fourier coefficients, rise times, slopes of color- magnitude plots, etc.) but others, such as the presence of emission lines and line doubling or broadening, will be derived from spectra. Seven nights were allocated to the program in July 2001. About forty-five percent of the needed spectra were obtained.


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NOAO >   Observing Info >   Approved Programs >   2002B-0023

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