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

¹ Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
e-mail: Andrew.norton@open.ac.uk
² Astrophysics Group, Keele University, Staffordshire ST5 5BG, UK
³ Department of Physics, University of Warwick, Coventry CV4 7AL, UK

Received: 3 July 2015
Accepted: 12 January 2016

Abstract

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 ~ 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_⊙ and a radius of 2.41 ± 0.06 R_⊙, as well as a Roche-lobe filling secondary star with a mass of 0.41 ± 0.03 M_⊙ and a radius of 4.21 ± 0.11 R_⊙.

Conclusions. 1SWASP J050634.16–353648.4 is therefore a bright δ 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.