SuperWASP discovery and SALT confirmation of a semi-detached eclipsing binary that contains a δ Scuti star

Aims. We searched the SuperWASP archive for objects that display multiply periodic photometric variations. Methods. Specifically we sought evidence for eclipsing binary stars that display a further non-harmonically related signal in their power spectra. Results. The object 1SWASP J050634.16-353648.4 has been identified as a relatively bright (V similar to 11.5) semi-detached eclipsing binary with a 5.104 d orbital period that displays coherent pulsations with a semi-amplitude of 65 mmag at a frequency of 13.45 d(-1). Follow-up radial velocity spectroscopy with the Southern African Large Telescope confirmed the binary nature of the system. Using the PHOEBE code to model the radial velocity curve with the SuperWASP photometry enabled parameters of both stellar components to be determined. This yielded a primary (pulsating) star with a mass of 1.73 +/- 0.11 M-circle dot and a radius of 2.41 +/- 0.06 R-circle dot, as well as a Roche-lobe filling secondary star with a mass of 0.41 +/- 0.03 M-circle dot and a radius of 4.21 +/- 0.11 R-circle dot. Conclusions. 1SWASP J050634.16-353648.4 is therefore a bright delta Sct pulsator in a semi-detached eclipsing binary with one of the largest pulsation amplitudes of any such system known. The pulsation constant indicates that the mode is likely a first overtone radial pulsation.