Long-term variability of the SX Phoenicis star CY Aquarii^*

Astronomy Group, Vrije Universiteit Brussels (VUB), Pleinlaan 2, 1050 Brussels, Belgium e-mail: csterken@vub.ac.be

Corresponding author: J. N. Fu, jianfu@vub.ac.be

Received: 4 April 2003
Accepted: 18 April 2003

Abstract

We present 23 new times of maximum light of the SX Phoenicis star CY Aquarii. The O–C diagram reveals a new value of the period since 1996. CY Aqr is the first SX Phe star where the major component of the long-term period change can be represented without invoking large-amplitude period jumps. A linear period change combined with the light-time effect in a highly-eccentric orbit yields a reasonably precise solution. The binary explanation, however, does not account for the full magnitude of the period changes, and small residuals in the time interval 1930–1950 seem to remain.