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Astron. Astrophys. 322, 751-755 (1997)

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Procedure to find [FORMULA], [FORMULA] and [FORMULA] for Cepheids from isolated observations using the complete light curve in V

L. Labhardt 1, A. Sandage 2 and G.A. Tammann 1

1 Astronomical Institute, University of Basel, Venusstrasse 7, CH-4102 Binningen, Switzerland
2 The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101, USA

Received 9 May 1996 / Accepted 29 November 1996


The successful discovery of Cepheids in nearby galaxies with HST has triggered the development of a both simple and effective method to determine mean magnitudes from a few scattered measurements in combination with the complete light curve observed in V. Based on the empirically derived variation of the scaled difference of magnitude deflections at two passbands with phase, correction values are obtained to transfer the complete light curve in V into light curves in B, R and I, respectively. Applied to isolated observations, the procedure yields a mean magnitude for each phase point observed at that passband. With three to four measurements, the accuracy of the final mean magnitude obtained for Cepheids with normal light curves is comparable to the value obtained from complete light curves.

Key words: methods: data analysis – techniques: photometric – stars: fundamental parameters – Cepheids

Send offprint requests to: L. Labhardt

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© European Southern Observatory (ESO) 1997

Online publication: June 5, 1998