PHOTOMETRIC PROPERTIES FOR SELECTED ALGOL-TYPE BINARIES. VI. THE NEWLY DISCOVERED oEA STAR FR ORIONIS

Abstract

New photometry of the neglected eclipsing binary FR Orionis was obtained in 2012 November and December. Using the updated Wilson–Devinney program, the photometric elements were deduced from two-color light curves. The results indicate that this system is a semi-detached binary, with a mass ratio of 0.325(±0.002) and a fill-out factor of the primary of fp = 73.5(±0.2)%. The oscillating light curves imply that FR Ori may be an oscillating EA (oEA)-type star with a rapidly pulsating, mass-accreting primary component. After we removed the theoretical light curves from the observations, Fourier analysis revealed that the more massive component possibly shows a δ Scuti type pulsation with four detected frequencies. The dominant frequency is f1 = 38.6c day −1 (i.e., Ppuls = 37.3 minutes), and the pulsation constant is Q = 0.014 days. Based on all available eclipsing times, the orbital period is undergoing a secular period increase with a rate of dP/dt = +8.85(±0.66) × 10 −8 day yr −1 , which may be interpreted by mass transfer from the secondary to the primary. We expect that the more massive component will fill its Roche lobe due to mass transfer of the secondary. Therefore, the oEA star FR Ori may evolve into a contact configuration.