Analysis of Data Gathered by Hipparcos Satellite on Cepheid Variable Stars.Quantifying the shapes of Cepheid variable Cepheid variable One of a class of variable stars whose period of variation is closely related to its luminosity and is therefore useful in measuring the distances to clusters of stars and galaxies. star light curves is a technique that has been in use for the past several decades. Work to date has been primarily done for a few stars observed at a single site or by compiling the data for many stars from various sites. The availability of photometry photometry (fōtŏm`ətrē), branch of physics dealing with the measurement of the intensity of a source of light, such as an electric lamp, and with the intensity of light such a source may cast on a surface area. from the Hipparcos satellite presents the opportunity to utilize a homogenous homogenous - homogeneous data set to calculate the Fourier parameters. Light curves of 135 classical Cepheids observed by Hipparcos were decomposed de·com·pose v. de·com·posed, de·com·pos·ing, de·com·pos·es v.tr. 1. To separate into components or basic elements. 2. To cause to rot. v.intr. 1. . The Hipparcos periods were used and the light curves were categorized into four groups based on the completeness of phase coverage. There were 28 stars with very good phase coverage, 23 with good, 44 with fair, and 40 with poor. The Fourier parameters were then calculated using from two to seven harmonics depending on the asymmetry Asymmetry A lack of equivalence between two things, such as the unequal tax treatment of interest expense and dividend payments. of the light curve. For those Cepheids with adequate phase coverage the results are presented in terms of amplitude ratios and phase differences. Through examination of these results it can be seen that further use of Hipparcos data is warranted in the study of Cepheid variable stars. Kwayera Davis South Carolina Governor's School for Science and Mathematics |
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