EDP Sciences
Free access
Volume 402, Number 2, May I 2003
Page(s) 733 - 743
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20030291

A&A 402, 733-743 (2003)
DOI: 10.1051/0004-6361:20030291

A photometric monitoring of bright high-amplitude $\delta$ Scuti stars

II. Period updates for seven stars
A. Derekas1, 2, 3, L. L. Kiss2, 3, P. Székely1, E. J. Alfaro4, B. Csák1, Sz. Mészáros1, E. Rodríguez4, A. Rolland4, K. Sárneczky5, 3, Gy. M. Szabó1, K. Szatmáry1, M. Váradi1 and Cs. Kiss6

1  Department of Experimental Physics and Astronomical Observatory, University of Szeged, Dóm tér 9, Szeged 6720, Hungary
2  School of Physics, University of Sydney 2006, Australia
3  Guest observer at Konkoly Observatory, Hungary
4  Instituto de Astrofísica de Andalucía, CSIC, PO Box 3004, 18080 Granada, Spain
5  Astronomical Observatory, Szeged, Hungary
6  Konkoly Observatory of the Hungarian Academy of Sciences, PO Box 67, 1525 Budapest, Hungary

(Received 20 January 2003 / Accepted 21 February 2003 )

We present new photometric data for seven high-amplitude $\delta$ Scuti stars. The observations were acquired between 1996 and 2002, mostly in the Johnson photometric system. For one star (GW UMa), our observations are the first since the discovery of its pulsational nature from the Hipparcos data. The primary goal of this project was to update our knowledge on the period variations of the target stars. For this, we have collected all available photometric observations from the literature and constructed decades-long O-C diagrams of the stars. This traditional method is useful because of the single-periodic nature of the light variations. Text-book examples of slow period evolution (XX Cyg, DY Her, DY Peg) and cyclic period changes due to light-time effect (LITE) in a binary system (SZ Lyn) are updated with the new observations. For YZ Boo, we find a period decrease instead of increase. The previously suggested LITE-solution of BE Lyn (Kiss & Szatmáry 1995) is not supported with the new O-C diagram. Instead of that, we suspect the presence of transient light curve shape variations mimicking small period changes.

Key words: stars: variables: general -- stars: oscillations -- $\delta$ Sct

Offprint request: L. L. Kiss, laszlo@physics.usyd.edu.au

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