RT Sculptoris

In 1908, this system was discovered to be an eclipsing variable of the Beta Lyrae type by Ida Whiteside,^[8] a volunteer observer at Harvard College Observatory.^[9] It showed continuous variability with two maxima and two minima, having a period of 0.511574 days.^[8] By 1925, the period had been refined to 0.51156935±0.00000009 days, with the interval between the primary and secondary minima being only 45% of the period from one primary minimum to the next.^[10]

By 1958, it became evident that the orbital period of RT Sculptoris was not constant. The period measured in October 1954 had decreased to 0.51156249 days, or one second shorter over a period of 50 years. The light curve for the system showed the two maxima are slightly unequal and are not flat topped.^[11] The pair undergo partial eclipses with the primary minimum being caused by an occultation. The secondary minimum was found to be displaced and asymmetrical, showing a steeper descent on the descending branch compared to the ascending branch.^[12]

This system was found metal-deficient compared to the Sun.^[6] It was proposed that the confirmed period change could be explained by a mass exchange between the two components. In this model, the higher mass component is filling its Roche lobe, forming a semi-detached binary.^[13] The overflow is being accreted by the secondary, creating a small hot spot. The mass transfer rate is estimated at 1.3×10⁻⁸ M_☉ per year. The primary appears to be a late A-type star, while there is some disagreement about the secondary; the latter has been modelled as an F-, G- and even K-type star.^[5]