Search for evolutionary changes in Cepheid periods using the Harvard plate collection: NSV 9159 |
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Authors: | L. N. Berdnikov E. N. Pastukhova D. G. Turner D. J. Majaess |
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Affiliation: | (1) Sternberg Astronomical Institute, Universitetskii pr. 13, Moscow, 119992, Russia;(2) Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya ul. 48, Moscow, 109017, Russia;(3) Saint Mary’s University, 923 Robie Str., Halifax, Nova Scotia, B3H 3C3, Canada |
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Abstract: | We have obtained 530 photographic magnitude estimates for the long-period classical Cepheid NSV 9159 (P = 39d) in the plate collections of the Harvard Observatory and the Sternberg Astronomical Institute. Together with the currently available CCD observations from the ASAS-3 catalog, our data have allowed us to construct an O-C diagram spanning a time interval of 119 years. The O-C diagram has the shape of a parabola, which has made it possible to determine for the first time the quadratic light elements and to calculate the rate of evolutionary decrease in the period, 314.4 (±7.3) s yr?1, in agreement with the results of theoretical calculations for the second crossing of the instability strip. The available data reduced by the Eddington-Plakidis method do not reveal any noticeable random fluctuations in the period. |
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Keywords: | Cepheids period variability stellar evolution |
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