AAVSO: American Association of Variable Star Observers

The Southern Solar-type, Totally Eclipsing Binary PY Aquarii

Volume 47 number 1 (2019)

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Ronald G. Samec
Faculty Research Associate, Pisgah Astronomical Research Institute, 1 PARI Drive, Rosman, NC 28772; ronaldsamec@gmail.com
Heather A. Chamberlain
Pisgah Astronomical Research Institute, 1 PARI Drive, Rosman, NC 28772
Walter Van Hamme
Department of Physics, Florida International University, Miami, FL 33199


We obtained new BVRI (Bessell) observations of the solar-type eclipsing binary PY Aqr in 2017 with the 0.6-m SARA South reflector located at Cerro Tololo Inter-American Observatory. A simultaneous Wilson-Devinney solution of the new 2017 light curves, the 2003 discovery curve, and the 2001–2009 ASAS light curve reveals a system configuration with a modest degree of over-contact (fill-out ≈ 18%) and total eclipses (duration ≈ 23 minutes). The photometrically determined mass ratio is ≈ 0.32. The temperature difference between the components is ≈ 130K, indicating two stars in reasonably good thermal contact. Light curve asymmetries are modeled with a cool spot region on the primary, more massive star. Spanning a 16-year time base, the light curves indicate a 0.049 ± 0.005 s/yr steady increase of the orbit period. This dp/dt is not unusual as compared to the unpublished poster paper at the 2018 IAU GA study of over 200 solar type binaries. Two methods were used in conducting the period study, the p and dp/dt parameters in the Wilson program and a Wilson program means of generating eclipse timings from discovery and patrol based observations.