Proposal #148

As per John Percy's paper in JAAVSO Vol 48, No. 2, during the last century, V725 Sgr gradually changed from a 12-day Cepheid to an 85-day yellow semiregular giant. His analysis confirms that the previously-identified pulsation period has increased from about 50–60 days to 80–90 days since 1982. In the ASAS-SN data, there appear to be both a 82.6-day period and a possible 160.0-day period, though the latter is not prominent after pre-whitening. If it is real, however, the two periods could be interpreted as a first overtone period and a fundamental period, respectively. Evidence for two (or more) periods can also be seen in the ASAS-SN light curve, and in the visual data. The total V range is 1.1 magnitude. Since recent results in the literature indicate that V725 Sgr is a K4 yellow giant, it should be classified as a SRd variable. In view of its continuing changes, Percy notes that it needs and deserves to be monitored more systematically. He notes that AAVSO visual observations are sparse, and AAVSO CCD observations are apparently non-existent. He also concludes "In view of the interesting and complex behavior of this star in the last few years, and the uniqueness of a star which is changing before our eyes, we again urge observers to monitor this star regularly, with CCD techniques and multicolour filters if possible. It needs and deserves such systematic monitoring."

This proposal is therefore based on a systematic programme of BVRI photometry using OC61 initially over a period of 3 years and observed on every available clear night. the results can be used to extend Percy's analysis and conclusions.