New periodic variable stars coincident with ROSAT sources discovered using SuperWASP^*

¹ Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK e-mail: a.j.norton@open.ac.uk
² Department of Physics, University of Warwick, Coventry CV4 7AL, UK
³ Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK
⁴ Astrophysics Research Centre, Main Physics Building, School of Mathematics & Physics, Queen's University, University Road, Belfast BT7 1NN, UK
⁵ School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, UK
⁶ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁷ Astrophysics Group, School of Chemistry & Physics, Keele University, Staffordshire ST5 5BG, UK
⁸ Institute of Astronomy, University of Cambridge, Madingly Road, Cambridge CB3 0HA, UK
⁹ Department of Physics, University of Florida, Gainesville, FL 32611-8440, USA
¹⁰ Planetary & Space Sciences Research Institute, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
¹¹ Isaac Newton Group of Telescopes, Apartado de Correos 321, 38700 Santa Cruz de la Palma, Tenerife, Spain

Received: 11 January 2007
Accepted: 21 February 2007

Abstract

We present optical lightcurves of 428 periodic variable stars coincident with ROSAT X-ray sources, detected using the first run of the SuperWASP photometric survey. Only 68 of these were previously recognised as periodic variables. A further 30 of these objects are previously known pre-main sequence stars, for which we detect a modulation period for the first time. Amongst the newly identified periodic variables, many appear to be close eclipsing binaries, their X-ray emission is presumably the result of RS CVn type behaviour. Others are probably BY Dra stars, pre-main sequence stars and other rapid rotators displaying enhanced coronal activity. A number of previously catalogued pulsating variables (RR Lyr stars and Cepheids) coincident with X-ray sources are also seen, but we show that these are likely to be misclassifications. We identify four objects which are probable low mass eclipsing binary stars, based on their very red colour and light curve morphology.