The OmegaWhite Survey for short period variable stars – II. An overview of results from the first four years

• Published in: Monthly notices of the Royal Astronomical Society Vol. 463; no. 1; pp. 1099 - 1116
• Main Authors: Toma, R., Ramsay, G., Macfarlane, S., Groot, P. J, Woudt, P. A., Dhillon, V., Jeffery, C. S., Marsh, T., Nelemans, G., Steeghs, D.
• Format: Journal Article
• Language: English
• Published: London Oxford University Press 21.11.2016
• Subjects: Aerial surveys; Astronomy; Binary stars; Diffraction; Planes; Samples; Space telescopes; Stars; Stars & galaxies; Statistical analysis; Statistical methods; Variable stars; surveys; binaries: close; Galaxy: bulge; methods: observational; methods: data analysis; techniques: photometric
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stw2079

OmegaWhite is a wide-field, high cadence, synoptic survey targeting fields in the southern Galactic plane, with the aim of discovering short period variable stars. Our strategy is to take a series of 39 s exposures in the g band of a 1 deg2 of sky lasting 2 h using the OmegaCAM wide field imager on the VLT Survey Telescope (VST). We give an overview of the initial 4 yr of data which covers 134 deg2 and includes 12.3 million light curves. As the fields overlap with the VLT Survey Telescope Hα Photometric Survey of the Galactic plane and Bulge (VPHAS+), we currently have ugriHα photometry for ∼1/3 of our fields. We find that a significant fraction of the light curves have been affected by the diffraction spikes of bright stars sweeping across stars within a few dozen of pixels over the two hour observing time interval due to the alt-az nature of the VST. We select candidate variable stars using a variety of variability statistics, followed by a manual verification stage. We present samples of several classes of short period variables, including: an ultra compact binary, a DQ white dwarf, a compact object with evidence of a 100 min rotation period, three CVs, one eclipsing binary with an 85 min period, a symbiotic binary which shows evidence of a 31 min photometric period, and a large sample of candidate δ Sct type stars including one with a 9.3 min period. Our overall goal is to cover 400 deg2, and this study indicates we will find many more interesting short period variable stars as a result.