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Astron. Astrophys. 326, 698-708

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Period changes of AR Lacertae between 1900 and 1989

L. Jetsu1, I. Pagano2, D. Moss3, M. Rodonò2,4, A.F. Lanza2, and I. Tuominen5

1NORDITA, Blegdamsvej 17, DK-2100 Copenhagen, Denmark
2Osservatorio Astrofisico di Catania, Città Universitaria, I-95125, Catania, Italy
3Mathematics Department, The University, Manchester M13 9PL, UK
4Istituto di Astronomia, Università degli Studi, Viale A. Doria, 6, I-95125 Catania, Italy
5Department of Geosciences and Astronomy, University of Oulu, P.O. Box 333, FIN-90571 Oulu, Finland

Received 6 June 1996 / Accepted 29 April 1997


The epochs of the primary and secondary minima of AR Lac between 1900 and 1989 are analysed with two nonparametric methods of searching for periodicity in a weighted time point series. An analytical model for transforming the OC data of eclipsing binaries into the period domain is presented and is applied to AR Lac. The abrupt period changes of AR Lac reported in several previous studies are most probably a consequence of an oversimplified interpretation of the OC data, since these changes are as likely to be continuous, and even the possibility of a 36y cycle in the period cannot be definitely ruled out.

Key words: stars: AR Lacertae - binaries: eclipsing - methods: analytical; statistical

Send offprint requests to: L. Jetsu (jetsu@nordita.dk)

© European Southern Observatory (ESO) 1997

Online publication: September 18, 1997
Last change: October 15, 1997