Observations and analysis of the Southern binary R Arae

Abstract

This paper investigates the nature of the relatively bright (≃ 7th magnitude) eclipsing variable R Arae (HD 149730A), which has an orbital period of 4d.42509, from the analysis of photometricUBV observations. The main objective behind such an analysis is to determine whether the system qualifies for a classical Algol of semi-detached status. An analysis has been performed twice on each of theUBV curves as well as the light curve due to Gaposchkin, utilising a light curve optimisation procedure. In the first analysis the presence of the visual companion (HD 1497330B) to R Arae (angular separation = 3′'.6), whose light was present in all observations, was not accounted for. The second analysis attempts to account for this third light source. All the analyses indicate the relative radius of the secondary star, is of the order of 0.20. This value is well below the limit which would classify the system as a semi-detached binary. These results do, however, seem to be somewhat discordant with the spectroscopic and general photometric nature of the system, all of which suggest mass transfer processes to be occuring (therefore a possible semi-detached status). This is seen in several features, especially a marked increase in the system's mean orbital period, which tends to corroborate mass transfer from the secondary star.