AAVSO: American Association of Variable Star Observers

The Eclipsing Triple Star System b Persei (HD 26961) (Abstract)

Volume 47 number 2 (2019)

Donald F. Collins
Emeritus Professor of Physics, Warren Williams College, 701 Warren Wilson Road, Swannanoa, NC 28778


(Abstract only) The triple star system, b Persei (HD 26961, HR 1324, HIP 20070, SAO 24531), magnitude 4.6 V, spectral class A1 III, consists of two non-eclipsing stars in a close orbit (1.52-day period) and a third star that orbits the inner pair with a period of approximately 700 days. Many AAVSO observers have been observing high time-resolved eclipses or transits of the third star transiting both behind the inner pair (secondary eclipse) and in front of the inner pair (primary eclipse) since the first observations in February 2013. The AAVSO eclipse light curve observations have refined the measured period for the third star’s orbit to be 704.9 ± 0.1 d, a significant departure from the earlier spectroscopic radial velocity observations of 701.8 ± 0.4 d (Hill, et al. 1976, AJ 208, 152). A simple simulation of the light curves was developed to fit the timings of the dips in the light curves by adjusting a limited number of the orbital parameters for the star system. It is hoped to continue observing these transits to examine a possible evolution of the orbits and to obtain better knowledge of the astrophysical parameters for the three separate stars in the system.