Period study of the δ Scuti variable DE Lac

S.-M. Wang,1,2,3* S.-B. Qian,1,2,3 W.-P. Liao,1,2 J. Zhang,1,2 X. Zhou,1,2,3 and E.-G. Zhao1,2
1Yunnan Observatories, Chinese Academy of Sciences, P. O. Box 110, 650011 Kunming, China
2Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences
3University of the Chinese Academy of Sciences, Yuquan Road 19#, Shijingshan Block, 100049
Beijing, P. R. China
Received: May 05 2014 | Accepted: June 08 2014

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Abstract

DE Lac is a high-amplitude δ Scuti variable with a period of 0:253694 days. New CCD photometric monitoring of DE Lac was carried out on 2013 December 18 and 2014 January 5, by using the 1.0-m reflecting telescope at Yunnan Observatories. Photometric observations of DE Lac were also obtained by using the 85-cm telescope at Xinglong Station of National Astronomical Observatory. By using a few new determined times of maximum light together with those collected from the literature, the period changes in Observed-Calculated (O - C) diagram are analyzed. We discover that the pulsating period of DE Lac is increasing continuously at a rate of ˙P = +3.7 × 10-8 days/year. It is compatible with the prediction from the stellar evolution model calculations. Meanwhile, we collect other δ Scuti stars that have exhibited period changes.

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Keywords : techniques: photometric – stars: variable: δ Scuti – stars: individual: DE Lacertae